CHINESE JOURNAL of CATALYSIS Vol

http://www.chxb.cn ISSN 0253-9837 CN 21-1195/O6

催 CODEN THHPD3

化

学报

CHINESE JOURNAL OF C AT ALYSIS ChineseChinese JournalJournal ofof CatalysisCatalysis

主编林励吾 2013 Editor-in-Chief LIN Liwu Vol. 34 No. 2 eray 03Vol. 34 No. 2 pages 283 February 2013

N 2

O 2

CO CO2

_ o 80 c

- O2 397

中国化学会催化学会会刊 Transaction of the Catalysis Society of China

2013年 2013 第34卷第2期 CHINESE JOURNAL OF CATALYSIS Vol. 34 No. 2 In This Issue

封面: Co3O4 中钴和氧的属性如同一个硬币的正反两面. 通过纳米材料

可控合成实现三价钴的表面富集, 可获取性能优异的 Co3O4 催化剂. 另一方

面, 余运波等报道了合适条件下的预处理有利于 Co3O4 表面氧空穴团的形成, 实现了 CO 的低温氧化. 见本期第 283–293 页.

Cover: The properties of cobalt and oxygen ions in Co3O4 are just the two sides of the same coin. Using controlled synthesis of nano materials, Co3O4 enriched with surface Co3+ cations can be created, giving excellent catalytic performance. On the other hand, Yu and coworkers in their Article on pages 283–293 reported that pretreatment under suitable conditions favored the for-

mation of oxygen vacancy clusters on the Co3O4 surface, the presence of which guarantees CO oxidation at low temperatures.

About the Journal

Chinese Journal of Catalysis is an international journal published monthly by Chinese Chemical Society, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, and Elsevier. The journal publishes original, rigorous, and scholarly contributions in the fields of heterogeneous and homogeneous catalysis in English or in both English and Chinese. The scope of the journal includes:  New trends in catalysis for applications in energy production, environmental protection, and production of new materials, petroleum chemicals, and fine chemicals;  Scientific foundation for the preparation and activation of catalysts of commercial interest or their representative models;  Spectroscopic methods for structural characterization, especially methods for in situ characterization;  New theoretical methods of potential practical interest and impact in the science and applications of catalysis and catalytic reaction;  Relationship between homogeneous and heterogeneous catalysis;  Theoretical studies on the structure and reactivity of catalysts.  The journal also accepts contributions dealing with photo-catalysis, bio-catalysis, and surface science and chemical kinetics issues related to catalysis.

Types of Contributions Impact Factor

 Reviews deal with topics of current interest in the areas covered by this journal. Re- 2011 SCI Impact Factor: 1.171 views are surveys, with entire, systematic, and important information, of recent progress 2011 SCI 5-Year Impact Factor: 0.945 in important topics of catalysis. Rather than an assemblage of detailed information or a 2011 ISTIC Impact Factor: 1.288 complete literature survey, a critically selected treatment of the material is desired. Un- Abstracting and Indexing solved problems and possible developments should also be discussed. Authors should have published articles in the field. Reviews should have more than 80 references. Abstract Journals (VINITI)  Communications rapidly report studies with significant innovation and major academic Cambridge Scientific Abstracts (CIG) value. They are limited to four Journal pages. After publication, their full-text papers Catalysts & Catalysed Reactions (RSC) can also be submitted to this or other journals. Current Contents/Engineering, Computing  Articles are original full-text reports on innovative, systematic and completed research and Technology (Thomson ISI) on catalysis. Chemical Abstract Service/SciFinder  Highlight Comments describe and comment on very important new results in the orig- (CAS) inal research of a third person with a view to highlight their significance. The results Chemistry Citation Index should be presented clearly but concisely without the comprehensive details required of (Thomson ISI) an original article. Highlight comment should not be more than 2–3 Journal pages (ap- Japan Information Center of Science and proximately 9000 characters) in length, and should be appropriately organized by the Technology author. Chemical formulae, figures, and schemes should be restricted to important ex- Journal Citation Reports/Science Edition amples. The number of references should be restricted to about 15. (Thomson ISI)  Academic Arguments can discuss, express a different opinion or query the idea, con- Science Citation Index Expanded cept, data, data processing method, characterization method, computational method, or (Thomson ISI) the conclusion of published articles. The objective of an academic argument should be SCOPUS (Elsevier) to enliven the academic atmosphere. Web of Science (Thomson ISI)

2013年 2013 第34卷第2期 CHINESE JOURNA OF CATALYSIS Vo l . 3 4 No. 2

《催化学报》第四届编辑委员会月刊 SCI 收录 1980 年 3 月创刊中国化学会催化学会会刊 The Fourth Editorial Board of Chinese Journal of Catalysis 2013年2月20日出版顾问 (Advisors)

主管中国科学院蔡启瑞 (CAI Qirui) 辛勤 (XIN Qin) Bernard DELMON (比利时) 主办中国化学会闵恩泽 (MIN Enze) 胥诲熊 (XU Huixiong) Gerhard ERTL (德国) 中国科学院大连化学物理研究所彭少逸 (PENG Shaoyi) Jürgen CARO (德国) Masaru ICHIKAWA (日本) 主编林励吾宋春山 (SONG Chunshan, 美国) Michel CHE (法国) 编辑《催化学报》编辑委员会出版主编 (Editor-in-Chief)

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伏义路沈之荃杨启华 Publication Monthly (12 issues) (FU Yilu) (SHEN Zhiquan) (YANG Qihua) Started in March 1980 高滋 (GAO Zi) 申文杰 (SHEN Wenjie) 杨维慎 (YANG Weishen) Transaction of the Catalysis Society of China 关乃佳 (GUAN Naijia) 苏宝连 (SU Baolian, 比利时) 杨向光 (YANG Xiangguang) Superintended by 郭新闻孙予罕余林 Chinese Academy of Sciences (GUO Xinwen) (SUN Yuhan) (YU Lin) Sponsored by 何鸣元 (HE Mingyuan) 万惠霖 (WAN Huilin) 袁友珠 (YUAN Youzhu) Chinese Chemical Society and Dalian 贺鹤勇 (HE Heyong) 王德峥 (WANG Dezheng) 张涛 (ZHANG Tao) Institute of Chemical Physics of CAS 胡友良 (HU Youliang) 王国祯 (WANG Guozhen) 赵进才 (ZHAO Jincai) Editor-in-Chief LIN Liwu Edited by Editorial Board of 贾继飞 (JIA Jifei, 美国 ) 王建国 (WANG Jianguo) 郑小明 (ZHENG Xiaoming) Chinese Journal of Catalysis 寇元 (KOU Yuan) 王祥生 (WANG Xiangsheng) Published by Science Press 编辑部成员 (Editorial Office Staff)

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(CUIHUA XUEBAO) CHINESE JOURNAL OF CATALYSIS 中国科学院科学出版基金资助出版月刊 SCI 收录 2013 年 2 月第 34 卷第 2 期

综述 361 (中) 351 (中) 碱土金属对锆基钙钛矿材料负载钌催化剂氨合成性能的影生物制造不同立体构型2,3-丁二醇: 合成机理与实现方法响沈梦秋, 纪晓俊, 聂志奎, 夏志芳, 杨晗, 黄和王自庆, 马运翠, 林建新, 王榕, 魏可镁

367 (中) 研究论文液相沉积法制备可磁分离复合光催化剂纳米球及其催化性 283 (英/中/封面文章) 能许士洪, 谭东栋, 鲁巍, 时鹏辉, 毕得福, 马春燕, 上官文峰焙烧与预处理条件对Co3O4催化氧化CO性能的影响余运波, 赵娇娇, 韩雪, 张燕, 秦秀波, 王宝义 373 (中) 294 (英) Cr掺杂对中孔MgF2酸性及孔结构的影响 ZSM-5沸石结晶度对乙苯叔丁基化对位选择性的影响牛怀成, 李利春, 李瑛, 郭荔, 唐浩东, 韩文锋, 刘化章 PUSHPARAJ Hemalatha, MANI Ganesh, MUTHIAHPILLAI Palanichamy, VELAYUTHAM Murugesan, PARK Yong-Ki, 379 (中) CHOI Won Choon, JANG Hyun Tae 介孔Ni-β-Mo2C/SBA-16催化剂在CH4/CO2重整制合成气反应中的催化性能 305 (英) 瑙莫汗, 付晓娟, 雷艳秋, 苏海全

Ni掺杂对纳米结构牡丹花状CeO2材料催化特性的影响仙存妮, 王少飞, 孙春文, 李泓, 陈晓惠, 陈立泉 385 (中) Pt/BiOCl纳米片的制备、表征及其光催化性能 313 (英/中) 余长林, 陈建钗, 操芳芳, 李鑫, 樊启哲, YU Jimmy C, 催化臭氧氧化降解邻苯二甲酸二甲酯中催化剂构效关系魏龙福王建兵, 王灿, 杨春丽, 王国庆, 祝万鹏 391 (中) 322 (英) Ru-Fe/C催化剂上邻氯硝基苯原位液相加氢性能

镍促进CuO-CeO2催化剂的结构表征及低温CO氧化活性许响生, 陈傲昂, 周莉, 李小青, 顾辉子, 严新焕陈国星, 李巧灵, 魏育才, 方维平, 杨意泉相关信息 330 (英) 复合氧化物载体对镍基催化剂上CO甲烷化反应性能的影响 293 2nd International Congress on Catalysis for Biorefineries 张罕, 董云芸, 方维平, 连奕新 (CatBior 2013) 321 第二届国际生物质催化炼制大会(CatBior 2013)第一轮 336 (英) 通知 Au/NTS-1催化丙烯气相直接环氧化 397 作者索引刘义武, 张小明, 索继栓

( ) Elsevier ScienceDirect 341 (英/中) 英文全文电子版国际版由出版社在上出版 http://www.sciencedirect.com/science/journal/18722067 Cu掺杂对介孔VOx-TiO2催化苯羟基化制苯酚的影响 http://www.elsevier.com/locate/chnjc 徐丹, 贾丽华, 郭祥峰 http://www.chxb.cn

(CUIHUA XUEBAO) CHINESE JOURNAL OF CATALYSIS Supported by the Science Publication Foundation of the CAS Monthly Vol. 34 No. 2 February 2013 Graphical Contents

Review

Chin. J. Catal., 2013, 34: 351–360 doi: 10.3724/SP.J.1088.2013.20737 Biotechnological production of 2,3‐butanediol stereoisomers: synthetic mechanism and realized methods SHEN Mengqiu, JI Xiaojun*, NIE Zhikui, XIA Zhifang, YANG Han, HUANG He* Nanjing University of Technology

OH OH OH Diacetyl Reductase H3C H3C H3C OR CH3 CH3 CH3 Catalysis O O meso-, (R, R), (S, S)-2,3- OH O OH Butanediol Dehydrogenase (S, S)-2,3-Butanediol H C H C 3 3 OH Biotechnological CH3 CH3 Whole cell catalysts Production of O OH H3C CH Racemic 3 2,3-Butanediol R, R)-, meso- 2,3-Butanediol OH Stereoisomers (R, R)-2,3-Butanediol Fermentation Acetoin Carbohydrates; Biodiesel derived glycerol… α-Acetolactate OH

H3C CH3 OH meso-2,3-Butanediol Synthetic metabolic pathways

The biological routes for the production of pure 2,3‐butanediol stereoisomers, including using the methods of whole cell catalysis and the emerging synthetic biology, was reviewed. In contrast to the conventional chemical methods, the biological methods own their great advantages.

Articles

Chin. J. Catal., 2013, 34: 283–293 doi: 10.1016/S1872‐2067(11)60484‐1

Influence of Calcination and Pretreatment Conditions on the Activity of Co3O4 for CO Oxidation YU Yunbo*, ZHAO Jiaojiao, HAN Xue, ZHANG Yan, QIN Xiubo, WANG Baoyi Research Center for Eco‐Environmental Sciences, Chinese Academy of Sciences; Institute of High Energy Physics, Chinese Academy of Sciences

20 100

80 -TPD (%) 2 15

60 10 40 measured by O by measured 2 5 20

Adsorbed O

0 0 conversion CO (h)Durability for 100% o o o Air, 150 C N2, 150 C N2, 200 C Pretreatment conditions

Pretreatment of Co3O4 in N2 at moderate temperatures promotes the formation of oxygen vacancy clusters, favoring the adsorption of oxygen molecules and guaranteeing a long durability for CO oxidation. Chin. J. Catal., 2013, 34: 294–304 doi: 10.1016/S1872‐2067(11)60482‐8 Effects of crystallinity of ZSM‐5 zeolite on para‐selective tert‐butylation of ethylbenzene PUSHPARAJ Hemalatha, MANI Ganesh, MUTHIAHPILLAI Palanichamy, VELAYUTHAM Murugesan, PARK Yong‐Ki, CHOI Won Choon, JANG Hyun Tae* Hanseo University, South Korea; Anna University, India; Korea Research Institute of Chemical Technology, South Korea

A fluoride medium offers defect‐free, highly crystalline ZSM‐5 crystals. High crystallinity confers high para selectivity (> 90%) in tert‐butylation of ethylbenzene. A fluoride medium is better than an alkaline medium for the commercial production of para‐selective ZSM‐5 catalysts.

Chin. J. Catal., 2013, 34: 305–312 doi: 10.1016/S1872‐2067(11)60466‐X

Effect of Ni doping on the catalytic properties of nanostructured peony‐like CeO2 XIAN Cunni, WANG Shaofei, SUN Chunwen, LI Hong*, CHAN Suiwai, CHEN Liquan Institute of Physics, Chinese Academy of Sciences, China; Columbia University, USA

100 Ni-doped PCO CO 80 CO2 Ni-loaded PCO 60

20 PCO CO conversion (%) conversion CO Ce Ni O C 0 60 90 120 150 180 210 240 270 300 Ni-doped peony-like CeO2 (PCO) o Temperature ( C)

Oxygen vacancies are generated in bulk ceria after Ni doping, which promotes the reducibility of peony‐like CeO2, and hence enhances the catalytic activity for CO oxidation.

Chin. J. Catal., 2013, 34: 313–321 doi: 10.1016/S1872‐2067(11)60479‐8 Relationship between the structure and activity of ruthenium catalysts in the catalytic ozonation of dimethyl phthalate WANG Jianbing*, WANG Can, YANG Chunli, WANG Guoqing, ZHU Wanpeng China University of Mining and Technology, Beijing Campus; Tsinghua University

80 80

60 60

o 20 500 C 20 300 W TOC removal (%) TOC removal (%) 0 C AC C C C C l-A ll- t-A t-A l-A l-A 0 hel she nu onu oa oa 0 20406080100 uts ut oco oc C u/C N u/N C u/C R R R Time (min)

H O Ru H O

H O Ru Activated carbon

The surface structure of the activated carbon (AC) support influenced the activity of Ru/AC catalysts in dimethyl phthalate ozonation. Microwave heating during catalyst preparation changed the catalyst activity by a modification of its surface structure.

Chin. J. Catal., 2013, 34: 322–329 doi: 10.1016/S1872‐2067(11)60468‐3

Low temperature CO oxidation on Ni‐promoted CuO‐CeO2 catalysts CHEN Guoxing, LI Qiaoling, WEI Yucai, FANG Weiping, YANG Yiquan* Xiamen University

The high catalytic activity of Ni‐promoted CuO‐CeO2 is due to the promoter giving increased amounts of Cu+ in the catalyst and the formation of solid solutions of Cu‐O‐Ce and Ni‐O‐Ce.

Chin. J. Catal., 2013, 34: 330–335 doi: 10.1016/S1872‐2067(11)60485‐3

Effects of composite oxide supports on catalytic performance CO + H2 CH4 + H2O of Ni‐based catalysts for CO methanation ZHANG Han, DONG Yunyun, FANG Weiping*, LIAN Yixin* Xiamen University NiO Strong Ni-Al Al2O3 interaction

CO + H2 CH4 + H2O

MOx adding

NiO/MOx‐Al2O3 (M = Mg, Si, Zr) catalysts for CO methanation, prepared using a modified grinding‐mixing method, have higher NiO catalytic activities than that of a conventional NiO/Al2O3 catalyst. Relatively weak This is attributed to the weakening of Ni–Al interactions after Al2O3 Ni-Al interaction adding MOx.

Chin. J. Catal., 2013, 34: 336–340 doi: 10.1016/S1872‐2067(11)60474‐9 Gold supported on nitrogen‐incorporated TS‐1 for gas‐phase epoxidation of propylene LIU Yiwu, ZHANG Xiaoming*, SUO Jishuan Chengdu Institute of Organic Chemistry, Chinese Academy of Sciences; Neijiang Normal University

A novel gold catalyst was prepared by immobilization of gold nanoparticles on nitrogen‐incorporated TS‐1. This catalyst exhibits an excellent catalytic capacity for gas‐phase epoxidation of propylene using H2 and O2. Nitrogen‐incorporation into TS‐1 improved both gold loading and dispersion, and decreased the acidic sites of the support surface. Chin. J. Catal., 2013, 34: 341–350 doi: 10.1016/S1872‐2067(11)60487‐7

Cu‐doped mesoporous VOx‐TiO2 for catalytic hydroxylation of benzene to phenol XU Dan, JIA Lihua*, GUO Xiangfeng* Qiqihar University

H2-TPR Cu loading

2.5%

1.1%

H O 2 2

Intensity 0.75% Cu VO x 0.36%

0.29% TiO2 0%

100 200 300 400 500 600 700 Temperature (oC)

Incorporation of Cu additives into a VOx/TiO2 catalyst improved the reducibility of VOx species, while Cu helped the monodispersion of VOx species on the TiO2 support surface.

Chin. J. Catal., 2013, 34: 361–366 doi: 10.3724/SP.J.1088.2013.20744 H

Effect of alkali earth mentals on performance of H zirconium‐based perovskite composite oxides supported ruthenium for ammonia synthesis + Ru WANG Ziqing, MA Yuncui, LIN Jianxin, WANG Rong, WEI Kemei N Fuzhou University Ru Ru

Ca/Sr/Ba

BaZrO3 was an excellent support for Ru‐based catalyst for ammonia synthesis compared with CaZrO3 and SrZrO3, which Zr o could significantly inhibit the adsorption of H2 and facilitate the N + 3H 2NH cleavage of N2. 2 2 3

Chin. J. Catal., 2013, 34: 367–372 doi: 10.3724/SP.J.1088.2013.20766 Photocatalytic properties of magnetically separable composite photocatalyst nanospheres prepared by liquid‐phase deposition XU Shihong*, TAN Dongdong, LU Wei, SHI Penghui, BI Defu, MA Chunyan, SHANGGUAN Wenfeng Donghua University; Beijing General Municipal Engineering Design & Research Institute; Shanghai Jiao Tong University

Surfactant AOT

TEOS (NH4)TiF6

NiFe O SiO @NiFe O TiO @SiO @NiFe O 2 4 2 2 4 2 2 2 4 A novel photocatalyst nanosphere TiO2@SiO2@NiFe2O4 was prepared by a reverse micelle method and liquid phase deposition technique. The prepared photocatalyst nanospheres show high photocatalytic activity.

Chin. J. Catal., 2013, 34: 373–378 doi: 10.3724/SP.J.1088.2013.20854 Effect of Cr‐doping on the acidity and pore structure of mesoporous magnesium fluoride NIU Huaicheng, LI Lichun, LI Ying*, GUO Li*, TANG Haodong, HAN Wenfeng, LIU Huazhang Zhejiang University of Technology; Zhejiang Chemical Industry Research Institute Co., Ltd.

CHClF2 CHCl3 + CHF3 HF 100 Cr doped MgF2 80 MgF2 60 Co-precipitation 40 Thermal treatment 20 Mg(NO3)2 Conversion (%) CrF3 0 Cr(NO ) 0 100 200 300 400 3 3 Mesoporous MgF / Cr doped MgF o 2 2 Temperature ( C) The Cr‐doping in mesoporous magnesium fluoride prepared by co‐precipitation increases the acidity and the specific surface area of magnesium fluoride and thus increases the catalytic performance in CHClF2 disproportionation.

Chin. J. Catal., 2013, 34: 379–384 doi: 10.3724/SP.J.1088.2013.20857 Catalytic performance of mesoporous material supported bimetallic carbide Ni‐‐Mo2C/SBA‐16 catalyst for CH4/CO2 reforming to syngas Naomohan, FU Xiaojuan, LEI Yanqiu, SU Haiquan* Inner Mongolia University

The catalyst Ni‐‐Mo2C/SBA‐16 in methane/carbon dioxide reforming reaction, which establishs carbonization‐oxidation circulation, exhibited high catalytic activity and remarkable

anti‐coke effect.

Chin. J. Catal., 2013, 34: 385–390 doi: 10.3724/SP.J.1088.2013.20904 Preparation, characterization, and photocatalytic properties of Pt/BiOCl nanoplates Potential YU Changlin*, CHEN Jianchai, CAO Fangfang, LI Xin, FAN Qizhe, -2 light YU Jimmy C, WEI Longfu -1 hv - - - CB Jiangxi University of Science and Technology; Fuzhou University; + Pt e e e - - (H2/H ) 0 O2 +1 - The Chinese University of Hong Kong ·O2 Pt +2 light E ≈3.47 eV + + hv g +3 Ptn+ +dye OH- BiOCl The presence of Pt nanoparticles could effectively separate the CO + H O + Pt +4 2 2 photo‐generated e–/h+ pairs and result in the plasmon h+ h+ h+ ·OH VB photocatalysis under visible light irradiation.

Chin. J. Catal., 2013, 34: 391–396 doi: 10.3724/SP.J.1088.2013.20959 NO2 Re Catalytic stability of ortho‐chloronitrobenzene ac ti hydrogenation on Ru‐Fe/C catalyst on Cl ion tivat H* CO Deac XU Xiangsheng, CHEN Ao’ang, ZHOU Li, LI Xiaoqing, GU Huizi, 2 YAN Xinhuan* Zhejiang University of Technology CO

NH2 FTS WGSR Cl H2 C2H5OH H O n 2 atio CO accumulation on the active centers of Ru‐based catalyst is the ner ege main reason for its deactivation, while the Fe additive can reduce R the CO amount to a minimum level through WGS and FTS reaction. Ru Fe Active carbon

Chinese Journal of Catalysis 34 (2013) 305–312 催化学报 2013年第34卷第2期 | www.chxb.cn

available at www.sciencedirect.com

journal homepage: www.elsevier.com/locate/chnjc

Article Effect of Ni doping on the catalytic properties of nanostructured peony‐like CeO2

a a a a, b a XIAN Cunni , WANG Shaofei , SUN Chunwen , LI Hong *, CHAN Suiwai , CHEN Liquan a Key Laboratory for Renewable Energy, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China b Department of Applied Physics and Applied Mathematics, Columbia University, New York, USA

ARTICLE INFO ABSTRACT

Article history: Nanostructured ceria materials have attracted wide attention as catalysts, and the doping of these Received 13 August 2012 materials with rare earth elements to modify their catalytic activity has been comprehensively in‐ Accepted 12 October 2012 vestigated. A novel type of Ni‐doped hierarchical nanostructured peony‐like ceria (PCO) has been Published 20 February 2013 prepared and its catalytic activity is investigated and compared with that of Ni‐loaded samples. The prepared Ni‐doped ceria have nanoscale grain sizes and open mesopores. This unique morphology Keywords: endows it with superior catalytic activity for the oxidation of CO and the partial oxidation of me‐ Nanostructured ceria thane. It is found that extra oxygen vacancies are generated in the ceria, and the reducibility of the Nickel ceria is highly enhanced after Ni‐doping. The catalytic activity for CO oxidation is improved after Carbon monoxide Ni‐doping, compared with that of pure ceria and Ni‐loaded ceria. In the reaction for the partial oxi‐ Oxidation dation of methane, the 3.8 atm% Ni‐loaded PCO sample realizes a higher CH4 conversion than the Methane Ni‐doped ceria. However, it is found that the onset temperature for CH4 conversion decreases from Partial oxidation 400 °C for the pure PCO and 3.8 atm% Ni‐loaded PCO sample, to 340 °C for the 5.7 atm% Ni‐doped PCO sample. © 2013, Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.

1. Introduction these materials as peony‐like CeO2 (PCO). The PCO‐based ma‐ terials have an open mesoporous microstructure. The thickness CeO2‐based materials have attracted much attention in re‐ of the petals is in the range of 20–50 nm, and the grain size is cent years, due to their high catalytic activity for CO oxidation approximately 6–8 nm. Their surface area is above 100 m2/g. [1–3], water‐gas shift reactions [4–6], reformation of hydro‐ Compared with commercial ceria, they show higher thermal carbons [7,8], and three‐way catalysis for the elimination of stability [16] and much higher activity for CO oxidation [14,15], toxic auto‐exhaust [6,9]. The excellent catalytic activity of ethanol reformation [17], and as active supporters in the anode CeO2‐based materials is related to the redox reaction of active layer and cathode layer in solid oxide fuel cells (SOFCs) CeIII/CeIV and the presence of intrinsic oxygen vacancies [18,19]. [10,11]. The catalytic activity can be significantly enhanced by The catalytic activity of CeO2 can also be modified signifi‐ changing the morphology of the catalysts [12,13]. Recently, cantly by metal loading. It has been found that CeO2 interacts hierarchical nanostructured ceria materials have been pre‐ with the loaded metal, and the interfacial interaction gives the pared using a hydrothermal method in our group [14,15]. They composite oxide unusual features compared with pure ceria have a similar morphology to the Chinese peony, so we named [20]. One of the most studied catalysts is Ni supported by

* Corresponding author. Tel.: +86‐10‐82648067; Fax: +86‐10‐82649046; E‐mail: [email protected] This work was supported by the National Natural Science Foundation of China (511172275) and the National Basic Research Program of China (973 Program, 2012CB215402). DOI: 10.1016/S1872‐2067(11)60466‐X | http://www.sciencedirect.com/science/journal/18722067 | Chin. J. Catal., Vol. 34, No. 2, February 2013 306 XIAN Cunni et al. / Chinese Journal of Catalysis 34 (2013) 305–312

CeO2‐based materials; this catalyst is effective in exploiting the 2. Experimental synergetic effects of Ni and CeO2. Nickel shows high activity for the reformation of hydrocarbons, similar to precious metals, 2.1. Catalyst preparation but with a much lower cost [21,22]. Nickel is also used as a catalyst for carbon nanotube growth because of its high cata‐ 2.1.1. Synthesis of Ni‐doped peony‐like ceria lytic activity for the cleavage of the C–C bond in hydrocarbons All of the doped peony‐like ceria materials were synthesized [23–25]. This also gives rise to the deactivation of the Ni‐based using the hydrothermal method described in our previous re‐ catalyst in the reformation of the hydrocarbons, due to the port [14]. In brief, hydrate cerium (III) nitrate (AR, 99%), hy‐ formation of carbon. Fortunately, the coking problem can be drate nickel nitrate (AR, ≥ 98%), glucose, acrylamide, and am‐ alleviated by modifying the properties of the support [24,26– monia aqueous solutions were purchased from Beijing Chemi‐ 28]. As an oxygen ion conductor, CeO2 has been demonstrated cal Reagents Company. The hexahydrated nickel nitrate was to be effective in impeding the formation of carbon; it achieves dissolved in de‐ionized water to obtain a solution with a Ni2+ this by transporting oxygen vacancies from the bulk to the sur‐ concentration of 0.2 mol/L. Then, hydrate cerium nitrate, the face, to promote the oxidation of carbon species [10,11]. Ac‐ Ni2+ solution (the total cation concentration was 0.005 mol, cordingly, Ni‐loaded CeO2 catalysts are widely used in wa‐ with molar ratios of dopant cation Ni2+ to Ce3+ of 0.05:0.95, ter‐gas shift reactions [4,29], the partial oxidation of methane 0.1:0.9, 0.15:0.85, and 0.2:0.8), 0.01 mol glucose, 0.015 mol (POM) [30–32], and the reformation of ethanol [17,33]. The acrylamide, and 80 ml of de‐ionized water were mixed in a most important component in this composite catalyst is be‐ Teflon autoclave with a capacity of 100 ml. The pH value of the lieved to be the metallic Ni, while the ceria support also plays a solution was then adjusted to approximately 10 via dropwise noticeable role. It has been confirmed that catalysts with CeO2 addition of an aqueous ammonia solution. After continuous support have higher activity and lower deactivation rates than stirring at room temperature for 3 h, the autoclave was sealed those with inert supports, such as Al2O3 or SiO2 [34–36]. The and kept in an oven at 180 C for 24 h. The precipitate was col‐ former benefits from the superior oxygen storage capacity and lected from the autoclave after the suspension was cooled to transport activity in the ceria. room temperature. After being washed with de‐ionized water The catalytic activity of ceria can be also modified by doping and alcohol and dried at 80 C, the Ni‐doped peony‐like ceria with Ga, La, Zr, Sn, Pr, or Cu [10,12,37]. The Cu‐doped ceria materials were obtained via calcining, using a previously re‐ material shows unusual structural and chemical properties that ported two‐step procedure [14]. favor the formation of oxygen vacancies, and can be reversibly reduced [37]. Taking this approach further, we expect that 2.1.2. Synthesis of Ni‐loaded peony‐like ceria Ni‐doped ceria materials would show some novel properties. The peony‐like CeO2 materials were synthesized using the However, it is difficult to dope Ni into the CeO2 lattice with a same process as that described in a previous paper [14]. The large molar ratio, due to the large discrepancy in ionic radius Ni‐loading was achieved using the nitrate impregnation meth‐ between Ce and Ni. This could be one of the reasons for the od. Peony‐like CeO2 (0.5 g) was added to 40 ml of de‐ionized relative lack of reports in the literature on Ni‐doped ceria. water, and after stirring at room temperature for 3 h, 855 μl Thurber et al. [38] studied the ferromagnetism of Ni doped into (5.7 atm% Ni content) of a 0.2 mol/L Ni2+ solution was added; 8 CeO2. It was claimed that the CeO2 retained its cubic fluorite h of additional, vigorous stirring was performed, and the sam‐ structure even when the Ni doping concentration reached as ple was dried at 80 C. The Ni‐loaded material was obtained high as 10 atm% of the nominal composition, and that the dop‐ after the sample was dried at 110 C for 2 h and calcined at 450 ing could decrease the grain size and generate additional strain C for 4 h in air. in the lattice. Jalowiecki‐Duhamel et al. [39] found that CeNixOy mixed oxides are large catalytic hydrogen reservoirs with 2.2. Characterization marked diffusion properties for hydrogen species. Yisup et al. [40] reported that Ce‐Ni‐O mixed oxides were highly active for X‐ray diffraction (XRD) measurements were carried out us‐ the catalytic oxidation of methane. Kaneko et al. [41] claimed ing a Holland X’Pert Pro MPD X‐ray diffractometer equipped that the reactivity in a two‐step water‐splitting reaction for with a monochromatized Cu Kα radiation source (λ = 0.15405 solar H2 production was improved by Ni‐doping in ceria. How‐ nm) operated at 40 kV and 40 mA using a step rate of 0.017. ever, none of these studies clarified this basic fact for Ni‐doped The morphology of the samples was observed using a scanning ceria; did the nickel really enter the lattice of the ceria? electron microscope (SEM, XL30s‐FEG, 10 kV). To determine The activities of Ni‐loaded and Ni‐doped ceria catalysts have the true amount of Ni doped into the CeO2, induced coupled been extensively studied [17,21,22,39–41], but the difference in plasma (ICP, Thermo Electron Corporation) analysis was used the catalytic activity between them is rarely reported. In this to test the chemical composition. The Raman spectra of the work, Ni‐doped peony‐like ceria catalysts were successfully Ni‐containing materials were recorded on a JY HR800 spec‐ prepared, and the effects of Ni doping on the structure and trometer at ambient temperature using a laser source of 514 catalytic activity of CeO2 were studied. For comparison, nm and resolution of 1 cm–1. The X‐ray photoelectron spec‐ Ni‐loaded PCO samples were also prepared at the same time. troscopy (XPS) analysis was performed on a PHI Quantera SXM The catalytic activities for CO oxidation and POM reactions instrument, using an Al X‐ray source, and the binding energies were also investigated. were calibrated using the binding energy of the C 1s (284.8 eV) XIAN Cunni et al. / Chinese Journal of Catalysis 34 (2013) 305–312 307 peak as a reference. Temperature‐programmed reduction 2:1:4 (for POM) was used. The total gas flow rate was 50 (TPR) was performed to determine the reduction behavior of ml/min for CO oxidation, and 49 ml/min for POM. The effluent the 5.7 atm% Ni‐doped and 3.8 atm% Ni‐loaded catalysts, using gas was analyzed using an online gas chromatograph (Agilent 10% H2‐90% Ar as the reducing gas on a Micromeritics Chem 7890a) equipped with Porapak Q, ShinCarbon ST, and a ther‐ 2920 instrument equipped with a thermal conductivity detec‐ mal conductivity detector (TCD). The conversions of CO and tor. The samples were heated from room temperature to 900 CH4 were calculated as: C at a rate of 10 C/min, and the gas flow rate was 50 ml/min. XCO = mol CO2out/(mol COout + mol CO2out) × 100% Typically, 20 mg of fresh catalyst was used in each experiment. XCH4 = (1 – mol CH4out/mol CH4in) × 100% A sample pretreatment was performed by flowing Ar over the sample at 300 C for 0.5 h, to remove the adsorbed species on 3. Results and discussion the surface. The H2 consumption was determined from the integrated peak area of the reduction profiles. 3.1. Characterization results of the catalysts

2.3. Catalytic testing All of the Ni‐doped ceria catalysts present a peony‐like nanostructure morphology, as shown in Fig. 1. Some small par‐ All of the Ni‐doped and Ni‐loaded samples were examined ticles can be clearly observed on the surface of the Ni‐loaded in the catalysis tests. Activity tests were performed under at‐ ceria sample. These are suggested to be residual Ni salt. As mospheric pressure, in a continuous down‐flow quartz listed in Table 1, the actual Ni contents in the samples with fixed‐bed reactor. The catalyst (50 mg) was loaded in the reac‐ nominal compositions of 5, 10, 15, and 20 atm% Ni doping tor, using quartz wool. A feed with a constant CO:O2:N2 volume were determined as 1.1, 3.2, 5.7, and 10.7 atm%, respectively, ratio of 2:3:95 (for CO oxidation), and CH4:O2:N2 volume ratio of using ICP analysis. Some of the Ni was lost during the washing

(a) (b)

Fig. 1. SEM images of the Ni‐doped peony‐like CeO2 (PCO) and 3.8 atm% Ni‐loaded PCO catalysts. (a) 1.1 atm% Ni doping; (b) 3.2 atm% Ni doping; (c) 5.7 atm% Ni doping; (d) 3.8 atm% Ni loading.

Table 1 Characterization results for the Ni‐doped/loaded peony‐like ceria catalysts.

e Ni content (atm%) Lattice CeO2 grain Surface element (atm%) Surface Ce/O ΔH2 NiO phase b Expected a ICP result parameter c (nm) size d (nm) O Ni ratio (%) P1 P2 P3 0 — no 0.54156 6.2 77.27 — 29.41 0 0.329 0.606 5D 1.1 no 0.54169 6.6 79.18 0 26.30 — — — 10D 3.2 no 0.54171 6.8 79.18 0 26.30 — — — 15D 5.7 no 0.54172 6.3 71.13 5.40 38.40 0.00387 0.471 0.585 20D 10.7 yes 0.54157 6.5 — — — — — — 5.7L 3.8 no 0.54122 10.9 75.89 13.99 31.77 0.116 0.0678 0.571 a The superscript D refers to doping, and L refers to loading. b From Fig. 2. c Calculated from the XRD data shown in Fig. 2 using the Jade program. d Calculated from the (111) XRD data for the ceria, as shown in Fig. 2. e From XPS. 308 XIAN Cunni et al. / Chinese Journal of Catalysis 34 (2013) 305–312

(5) NiO (4) (3) (2) (1) Intensity

(6) Intensity 440 460 480

(5) (4) (5)  2 (4) (3)  4 (2) (3)  (1) (2) 1.2 (1)  1/10 20 30 40 50 60 70 80 150 300 450 600 750 900 1050 1200 1350 1500 2/( o ) Raman shift (cm1) Fig. 2. XRD patterns of different catalyst samples. (1) Pure PCO; (2) 1.1 Fig. 3. Raman spectra of different catalyst samples. (1) Pure PCO; (2) atm% Ni‐doped PCO; (3) 3.2 atm% Ni‐doped PCO; (4) 5.7 atm% 3.8 atm%Ni‐loaded PCO; (3) 1.1 atm% Ni‐doped PCO; (4) 3.2 Ni‐doped PCO; (5) 10.7 atm% Ni‐doped PCO; (6) 3.8 atm% Ni‐loaded atm%Ni‐doped PCO; (5) 5.7 atm%Ni‐doped PCO. The small graph inset PCO. shows an enlargement of the peak at 450 cm–1. with water and alcohol. Figure 1(d) shows the Ni‐loaded PCO in all of the Ni‐doped samples, but is 10.9 nm in the 3.8 atm% catalyst with a nominal composition of 5.7 atm%. The actual Ni Ni loaded PCO, as shown in Table 1. After the impregnation content was 3.8 atm%. process, the 3.8 atm% Ni‐loaded PCO sample was calcined at The XRD patterns of the samples are shown in Fig. 2. The 450 C for 4 h in air to make the nickel nitrate decompose. This NiO phase is not found in the 3.8 atm% Ni‐loaded PCO catalyst, extra sintering also made the PCO grains grow bigger com‐ which could be due to the detection limit of the XRD measure‐ pared with those in the doped samples, which did not occur ments. It is not clear from these results whether some of the Ni extra sintering. was doped into the CeO2 lattice, or if it was all dispersed on the The Raman spectra are shown in Fig. 3. The peak at 462.0 surface. This will be clarified in a later section. All of the doped cm–1, the typical F2g Raman active modes of a fluorite struc‐ catalysts show a cubic fluorite structure. The NiO phase pre‐ tured ceria [43], shift to 455.2, 455.0, and 459.8 cm–1 for the sents only in the XRD pattern of the 10.7 atm% Ni‐doped PCO. 1.1, 3.2, and 5.7 atm% Ni‐doped samples, respectively. It does The lattice parameters of CeO2 increase with increasing of not shift for the Ni‐loaded sample. For clarity, an enlargement Ni‐doping amounts, as listed in Table 1. The NiII radius (0.069 of the spectra is shown in the inset. The red‐shift suggests a nm) is much smaller than that of CeIV (0.092 nm), and the lat‐ significant modification of the M–O bonding symmetry, which tice should shrink when Ni enters the CeO2 lattice. In fact, the probably results from the presence of Ni in the fluorite lattice conversion of CeIV (0.092 nm) to CeIII (0.103 nm) will happen [40,44]. As mentioned above, the doping of Ni into the ceria after the Ni‐doping. The increase in the amount of CeIII will ex‐ lattice results in extra strain and increases the concentration of pand the CeO2 lattice [38], which will counteract the shrinking CeIII in the bulk [38], which also influences the Raman bands. effects caused by the Ni‐doping. The more Ni doping that oc‐ The shoulder peaks around 230 and 590 cm–1 are related to the curs, the more CeIII is generated. Therefore, the CeO2 lattice addition of Ni. The relative intensity of the band from 540 to expands until the shrinking lattice effects of the NiII doping 636 cm–1 increases with increases in the Ni‐doping amount. begin to dominate. As shown in Table 1, the lattice parameters This is ascribed to the formation of oxygen vacancies in the of CeO2 decrease to 0.54157 nm under 10.7 atm% of Ni doping. Ni‐doped ceria [45]. These values are much smaller than those of the other The XPS spectra for the binding energies of Ce 3d and Ni 2p Ni‐doped samples. Although it is difficult to determine the real core levels are given in Fig. 4. The signals from CeIV are marked Ni‐doping content (due to the appearance of NiO impurities), it as u, u'', and u''' for 3d3/2, while those for 3d5/2 are marked as v, seems that the shrinking effects of the Ni‐doping overcome the v'', and v'''. The four peaks labeled as u0, u', v0, and v' were as‐ expanding effects of the increasing CeIII amounts after 10.7 signed to CeIII, as reported in the literature [46]. Although the atm% of Ni‐doping. It should be noted that the lattice parame‐ absolute binding energies are referenced against the C 1s pho‐ ters for the 3.8 atm% Ni‐loaded PCO is much smaller than those toelectron peak at 284.8 eV, some scattering of the binding of pure PCO, as listed in Table 1. After the impregnation pro‐ energies in the Ce 3d and Ni 2p regions could occur. This is due cess, the 3.8 atm% Ni‐loaded PCO sample was calcined at 450 to the low conductivity of the catalysts, which caused charging C in air for 4 h, to make the nickel nitrate decompose. Due to effects. Therefore, the positions of the peaks may not have re‐ extra sintering procedure in air, the amount of CeIII in the bulk flected the exact binding energies. However, it is clear from Fig. material of ceria decreases compared to pure ceria and hence 4(a) that the relative intensities of the v0/v, v', u0/u, and u' the lattice parameter of ceria decreases in this case [42]. peaks increase with increasing amounts of doped Ni. This be‐ The grain sizes in the prepared catalysts are calculated us‐ havior was not observed in the Ni‐loaded catalyst. The u0/u and ing the Scherrer equation. The grain size is approximately 6 nm v0/v peaks are too close to be distinguished, but from the in‐ XIAN Cunni et al. / Chinese Journal of Catalysis 34 (2013) 305–312 309

(a) u0,u (b) u''' Ce 3d Ni 2p3/2 (c) s v''' (2) O 1 (3) v0,v shoulder peak u' u'' ? (5) v' (4) v'' (4) 3.8 atm% (5) (1) (3) Ni-loaded PCO Intensity Intensity

(2) Intensity (1) 5.7 atm% Ni-doped PCO

880 890 900 910 920 930 850 855 860 865 870 875 526 528 530 532 534 Binding energy (eV) Binding energy (eV) Binding energy (eV) Fig. 4. Ce 3d (a), Ni 2p (b), and O 1s (c) XPS spectra of the samples. (1) Pure PCO; (2) 1.1 atm% Ni‐doped PCO; (3) 3.2 atm% Ni‐doped PCO; (4) 5.7 atm% Ni‐doped PCO; (5) 3.8 atm% Ni‐loaded PCO. CeIV peaks are marked as u, u'', and u''' for 3d3/2 and v, v'', and v''' for 3d5/2. The four peaks labeled as u0, u', v0, and v' were assigned to CeIII. crease of the relative intensity of the v' and u'' peaks, it is clear were also found in LaNiO3 [51]. The surface O contents are that the CeIII concentration increases with increasing Ni‐doping listed in Table 1. They slightly increase from 77.27% to 79.18% amounts. A similar phenomenon has been reported for Cu and after 1.1 atm% Ni or 3.2 atm% Ni doping, but rapidly reduce to Zr‐doped ceria materials [47,48]. 71.13% and 67.99% after 5.7 atm% Ni doping and 3.8 atm% Ni Compared with pure ceria, the v' and u' peak intensities for loading, respectively. The surface O content is closely related to the 3.8 atm% Ni‐loaded PCO show insignificant change com‐ the reduction of surface ceria [49]. According to the changes in pared with those of the 5.7 atm% Ni‐doped catalyst, which is in the ratio of Ce to O on the surface, as listed in Table 1, it is accordance with the Raman spectra results. The Ni contents on clearly that the Ni loading and doping reduce the surface oxy‐ the catalyst surface (as detected by XPS) are listed in Table 1. gen content. That is, they enhance the oxygen vacancy content There is no obvious Ni signal from the surfaces of the 1.1 atm% on the surface. However, it is found that the Ce/O ratio in the Ni‐doped or 3.2 atm% Ni‐doped catalysts, and the surface nick‐ 1.1 atm% Ni doping and 3.2 atm% Ni doping samples is a little el content is 5.4 atm% for the 5.7 atm% Ni‐doped sample, lower than that in PCO. In these two samples, the doped nickel which is similar to the bulk nickel content. In contrast, the sur‐ was not be detected using XPS. However, it is likely that the face nickel content is 13.44 atm% for the Ni‐loaded catalyst, nickel combines with the oxygen on the surface, which contrib‐ which is three times higher than the actual composition of 3.8 utes to the slightly lower Ce/O ratio of 26.30% in the 1.1 atm% atm%. This is consistent with the fact that the Ni particles are Ni doping and 3.2 atm% Ni doping samples, compared with of mostly dispersed on the surface of the 3.8 atm% Ni‐loaded PCO the value of 29.41% found for PCO. It is found that there are sample. In addition, it is found that the peak at approximately more oxygen vacancies on the surface of the 5.7 atm% Ni‐ 919.4 eV in the Ce 3d core level grows larger with increases in doped sample compared with the 3.8 atm% Ni‐loaded sample. the doped Ni amount. This is clearly related to the nick‐ According to the XRD, Raman spectroscopy, and XPS results el‐doping behavior, and the same peak is not observed in the given here, the lattice shrinking of CeO2 is induced after Ni spectra of the 3.8 atm% Ni‐loaded PCO. The Ni 2p spectra of the doping. To suppress the structure deformation, more CeIII is 5.7 atm% Ni‐doped and 3.8 atm% Ni‐loaded PCOs are com‐ generated, since its ionic radius is larger than that of CeIV. This pared in Fig. 4(b). In the Ni‐loaded catalyst, there are two dis‐ can explain the increases in the CeIII concentration after Ni tinct peaks at ~855.3 and ~861 eV, which were assigned to NiII. doping. According to the above results, the defect chemistry The peak at approximately 861 eV does not present, and the could be written in Kröger‐Vink notation as follows: ·· peak at approximately 855.3 eV broadens. This indicates the 2NiO + CeO2 = NiCeIV'' + 2VO + CeCeIV' + NiCeIII' + 2O2 different chemical environments surrounding the Ni in the loaded and doped catalysts. 3.2. TPR results The O 1s spectra of the samples are shown in Fig. 4(c). There are two peaks in the pure PCO and Ni‐doped PCO samples and The 5.7 atm% Ni‐doped PCO sample and the 3.8 atm% three peaks in the Ni‐loaded PCO sample. The O 1s peaks at Ni‐loaded PCO sample were selected to compare the influence 529.25 and 531.75 eV in PCO, which are assigned to the ce‐ of Ni doping and loading on the reduction properties of PCO. ria‐related lattice oxygen, and the adsorbed oxygen species on The TPR spectra are shown in Fig. 5 and the results are sum‐ the surface, respectively [49,50], shifted to 529.20 and 531.30 marized in Table 1. Two peaks are identified. The peak at 380 eV after 1.1 atm% Ni and 3.2 atm% Ni doping, and to 528.65 C (marked as P2) is attributed to the surface reduction of the and 530.95 eV after 5.7 atm% Ni doping. The O 1s peaks at ceria, and the second peak at 655 C (marked as P3) is related 528.10, 529.25, and 530.60 eV in the 3.8 atm% Ni‐loaded sam‐ to the bulk reduction of the ceria. The reduction temperatures ples and the new peak at 528.10 eV that was related to O2– are much lower than the reported temperatures of ~500 and 310 XIAN Cunni et al. / Chinese Journal of Catalysis 34 (2013) 305–312

P1 P3 638 220 P2 100 323 (3) 80 315 PCO 645 60 215 1.1 atm% Ni doped 3.8 atm% Ni loaded

(2)

consumption 40 2 655 3.2 atm% Ni doped H

5.7 atm% Ni doped 380 (1) CO conversion (%) conversion CO 20 13.4 atm% Ni loaded

0 200 400 600 800 60 90 120 150 180 210 240 270 300 330 Temperature (oC) Temperature (oC) Fig. 5. TPR profiles for the selected samples. (1) Pure PCO; (2) 5.7 Fig. 6. CO conversion for all Ni‐doped and Ni‐loaded PCO catalysts. The atm% Ni‐doped PCO; (3) 3.8 atm% Ni‐loaded PCO. catalyst (50 mg) was loaded in the reactor using quartz wool. A feed with a constant CO:O2:N2 volume ratio of 2:3:95 was used. The total gas flow rate was 50 ml/min. ~800 C [9,48]. When Ni is introduced, regardless of the doping or loading, the P2 and P3 shift to lower temperature. This 3.2 atm% Ni‐doped PCO. To further clarify why the effects of shows that the presence of Ni promotes the reduction of ceria. the Ni doping is superior to those of the Ni loading, a sample of In addition, the P1 below 300 C in the spectra of the 13.4 atm% Ni‐loaded PCO (actual composition) was also pre‐ Ni‐containing samples was assigned to the reduction of Ni [52]. pared using the impregnation method, and was tested for CO For the 5.7 atm% Ni‐doped PCO, the P1 may be related to the oxidation. The activity of the 13.4 atm% Ni‐loaded PCO is also reduction of Ni in the ceria close to the surface. The P2 for the lower than the activity of the 3.2 atm% Ni‐doped PCO and the Ni‐doped sample is at 315 C, much lower than that for PCO, 5.7 atm% Ni‐doped PCO. Therefore, the Ni doping is more ef‐ fective in enhancing the activity than the Ni‐loading. It has been which is at 380 C. The P2 peak consumes much more H2 for reduction on the Ni doped PCO catalyst than that on PCO. This reported that the releasable lattice oxygen on the ceria surface indicates that the Ni doping promotes the reduction of the ceria could be the key reactant for the oxidation of the adsorbed CO surface. The P2 for the 3.8 atm% Ni‐loaded PCO decreases to [12,53–56]. As shown in the TPR profiles in Fig. 5, the 3.8 atm% 323 C, indicating that interactions occur between the loaded Ni‐loaded PCO has more reducible Ni, but less reducible surface ceria than the 5.7 atm% Ni‐doped PCO sample. This result Ni and the surface of the ceria. However, the H2 consumption of the 3.8 atm% Ni‐loaded PCO is lower than that of PCO. This is supports the findings from previous investigations that the probably because the dispersion of Ni particles on the surface surface reducibility of CeO2 is an essential factor for CO oxida‐ partly blocks the reduction of the ceria. The P3 associated with tion, at least for ceria‐based catalysts [12,53–56]. the reduction of the bulk ceria does not shift significantly for Data for the partial oxidation of methane is shown in Fig. 7. either the 5.7 atm% Ni‐doped sample or the 3.8 atm% The CH4 conversion ratio of the Ni‐doped catalysts increases Ni‐loaded sample, and the P3 peak area for the three samples is with the increasing of the doped Ni amount. The activity of PCO similar, which shows that the Ni loading and doping have no significant influence on the reduction of bulk ceria. Comparing 35 the relative intensity of P1 to that of P2 and P3, it is quite clear PCO 30 1.1 atm% Ni doped that the amount of reducible Ni is higher in the 3.8 atm% 3.2 atm% Ni doped Ni‐loaded PCO sample than in the 5.7 atm% Ni‐doped PCO. This 25 5.7 atm% Ni doped is consistent with the XPS results showing that Ni is distributed 3.8 atm% Ni loaded uniformly within the lattice of the Ni‐doped sample. 20

15 3.3. Catalytic activity conversion (%) 4 10

The CO oxidation results are shown in Fig. 6. All of the CH 5 Ni‐containing catalysts show higher activities compared to the pristine PCO. It is clear that this improvement effect is not re‐ 0 lated to changes in the specific surface area of the catalyst since 300 330 360 390 420 450 480 510 540 570 600 the specific surface area of the pure PCO is above 100 m2/g Temperature (oC) [14,15], and is not significantly changed after small amounts of Fig. 7. Partial oxidation of CH4 on catalysts. The catalyst (50 mg) was Ni loading or doping. The catalytic activity of the Ni‐doped cat‐ loaded in the reactor, using quartz wool. A feed with a constant alyst increases with the increasing of the Ni doping amount. CH4:O2:N2 volume ratio of 2:1:4 was used. The total gas flow rate was 49 The activity of the 3.8 atm% Ni‐loaded PCO is lower than that of ml/min. XIAN Cunni et al. / Chinese Journal of Catalysis 34 (2013) 305–312 311 is similar to that of the 3.2 atm% Ni‐doped PCO for the temper‐ References ature range tested, and is slightly higher than the activity shown by the 1.1 atm% Ni‐doped PCO sample. The 5.7 atm% [1] Liu W W, Zhou K B, Wang L, Wang B Y, Li Y D. J Am Chem Soc, 2009, Ni‐doped PCO shows a 20% conversion ratio at 350 C. Com‐ 131: 3140 pared with the Ni‐doped PCO catalysts, the 3.8 atm% Ni‐loaded [2] Sun C W, Li H, Chen L Q. J Phys Chem Solids, 2007, 68: 1785 PCO sample shows a much higher conversion ratio of 28% at [3] Shan W J, Liu Ch, Guo H J, Yang L H, Wang X N, Feng Zh Ch. Chin J Catal (单文娟, 刘畅, 郭红娟, 杨利华, 王晓楠, 冯兆池. 催化学 540 C, which is also higher than the ratios shown by all of the 报), 2011, 32: 1336 doped and un‐doped PCO samples. Ni metal sites are known for [4] Carrettin S, Concepcion P, Corma A, Nieto J M L, Puntes V F. 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Graphical Abstract Chin. J. Catal., 2013, 34: 305–312 doi: 10.1016/S1872‐2067(11)60466‐X

100 Ni-doped PCO CO CO2 80 Ni-loaded PCO 60

20 PCO CO conversion (%) Ce Ni O C 0 Ni-doped peony-like CeO (PCO) 60 90 120 150 180 210 240 270 300 2 o Temperature ( C)

Oxygen vacancies are generated in bulk ceria after Ni doping, which promotes the reducibility of peony‐like CeO2, and hence enhances the catalytic activity for CO oxidation.

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Ni 掺杂对纳米结构牡丹花状 CeO2 材料催化特性的影响仙存妮 a, 王少飞 a, 孙春文 a, 李泓 a,*, 陈晓惠 b, 陈立泉 a a中国科学院物理研究所清洁能源重点实验室, 北京 100190 b哥伦比亚大学应用物理与应用数学学院, 美国纽约

摘要: 制备了一种新型 Ni 掺杂多层纳米结构牡丹花状 CeO2 材料, 研究了其催化性能, 同时与 Ni 负载牡丹花状 CeO2 样品进行了比

较. 结果表明, Ni 掺杂 CeO2 样品具有纳米晶粒和开放的介孔结构, 特殊的形貌使其在 CO 氧化和甲烷部分氧化反应中具有独特的

催化特性. Ni 掺杂后, CeO2 中产生了多余氧空位, 同时其氧化还原活性也增强, 其在 CO 氧化反应中的催化活性明显高于纯 CeO2 和

Ni 负载 CeO2 样品; 在甲烷部分氧化反应中, 牡丹花状 CeO2 负载 3 atm% Ni 催化剂样品上甲烷转化率高于所有 Ni 掺杂的催化剂样 o o 品. 但是在 Ni 负载型催化剂和花状 CeO2 催化剂上, 甲烷的起始转化温度为 400 C, 而 5.7 atm%Ni 的掺杂使其降至 340 C. 关键词: 纳米结构氧化铈; 镍; 一氧化碳; 氧化; 甲烷; 部分氧化

收稿日期: 2012-08-13. 接受日期: 2012-10-12. 出版日期: 2013-02-20. *通讯联系人. 电话: (010)82649047; 传真: (010)82649046; 电子信箱: [email protected] 基金来源: 国家自然科学基金 (511172275); 国家重点基础研究发展计划 (973 计划, 2012CB215402). 本文的英文电子版由Elsevier出版社在ScienceDirect上出版(http://www.sciencedirect.com/science/journal/18722067).