SYNTHESIS AND CHARACTERISATION OF GOLD NANOCLUSTERS FOR CATALYSIS APPLICATIONS Maria Leonor Rodrigues Alves UNIVERSITAT AUTÒNOMA DE BARCELONA DEPARTAMENT DE FÍSICA SYNTHESIS AND CHARACTERISATION OF GOLD NANOCLUSTERS FOR CATALYSIS APPLICATIONS PhD Thesis Maria Leonor Rodrigues Alves Directors: Dr. Ernest Mendoza Gómez Dr. Jordi Llorca Piqué Tutor: Dr. Jordi Pascual Gainza Barcelona, 2014 UNIVERSITAT AUTÒNOMA DE BARCELONA DEPARTAMENT DE FÍSICA SYNTHESIS AND CHARACTERISATION OF GOLD NANOCLUSTERS FOR CATALYSIS APPLICATIONS Thesis submitted by Maria Leonor Rodrigues Alves for the degree of Doctor in Materials Science Barcelona, 2014 Maria Leonor Rodrigues Alves Barcelona, Març 2014 El Dr. Ernest Mendoza Gómez, Professor Agregat del Departament de Física i Enginyeria Nuclear de la Universitat Politècnica de Catalunya, el Dr. Jordi Llorca Piqué, Professor Agregat de l’Institut de Tècniques Energètiques de la Universitat Politècnica de Catalunya, i el Dr. Jordi Pascual Gainza, Catedràtic del Departament de Física de la Universitat Autònoma de Barcelona. CERTIFIQUEN: La present tesis titulada: “Synthesis and characterisation of gold nanoclusters for catalysis applications” presentada per Maria Leonor Rodrigues Alves per optar al grau de Doctora en Ciència de Materials per la Universitat Autònoma de Barcelona ha estat realitzada sota la seva direcció en el Centre de Recerca en Nanoenginyeria de la Universitat Politècnica de Catalunya, i trobant-se conclosa, autoritzen la seva presentació perquè sigui avaluada pel tribunal corresponent. Dr. Ernest Mendoza Gómez Dr. Jordi Llorca Piqué Dr. Jordi Pascual Gainza (Director) (Director) (Tutor) To my mother, father, brothers and sister. ACKNOWLEDGEMENTS Firstly, I would like to thank Ernest Mendoza for many reasons. For always supporting me from the beginning and for always being available and believing in my work over the past four years. I am grateful for his enthusiasm, emparting knowledge in different fields, advice on how to improve my work and for having always closely followed my PhD research. I thank him for his kindness and humanity. Then, I thank Jordi Llorca, who contributed a lot since the second year of my PhD. I also thank him for his kindness and humanity, sharing his knowledge in different fields, for always being available and following the work closely. I thank Marta Santiago, for all her help, teaching, sharing of ideas and her kindness. I thank Belén Ballesteros for having taught me during the first year how to operate an HRTEM microscope; for all her patience, kindness, good teaching and help. I thank César Fernandéz, for all the help in the first year. I thank Trifon Trifonov, for all the help and for teaching me how to operate the SEM microscope. I thank Zaira Blazquez, Edurne Galindo, Nahikari Zuasti, Meritxell Molmeneu, Montserrat Domínguez, Alvaro Mayoral and Gemma Guilera, for their contributions to this thesis. I thank Lucília Salbany, for the help improving the language of this thesis. I thank Fundação para a Ciência e a Tecnologia, for the SFRH/BD/75925/2011 fellowship assigned to me. I thank Carlos, Sérgio, Arnau, Sunny, Neus and Jesús, for making my integration during my first year in Barcelona so much easier. I thank Núria, Cristian, Elena, Edu, Albert, Vanessa, Reinhold, David and César, for the time and moments that we shared every day at work. I thank Kasia, Magda, Pablito, Joa, Miriam, Sara, Fer, Francisco, Majo, Juan, Rox, Sebastián, Anita and Marcelo, for the good moments that we had during the time we were together in Barcelona. I thank Catarina, Cátia, Joana and João, for the friendship which we have maintained for nine years and for the mutual support even when we were living in three different continents and five different cities. I thank Filipe, Clara, Nuno and Susana, for the good moments that we always share each time we get together in Portugal. For the contact that we keep, the care and for being such good listeners. I thank David for always having the right words. I thank Maria, for being such a good example of courage and determination. I thank Raúl, Esteban, Felipe and Robert, for their support, friendship, help and mutual trust. I thank Diana and Rosa, for their support, care and for always being there to listen whenever I needed. I thank Ana, my sister, for having so much patience with me, for her help in improving my work and for always taking care of me. I thank Pedro, my brother, for the care, help and support, never judging me. I thank Zé, my brother, for the care. I thank my father, for the education and values that he has instilled in me during all these years. For the help in everything that I needed wherever I would be. I thank my mother, especially, because she is the one who suffered the most with my absence over the last four years. Thank you for being so kind, a good educator and for always supporting me. Because in the end, family is the only thing that is always present to defend and support you during the difficult moments. NOMENCLATURE AND ABREVIATIONS SYNTHESISED CATALYSTS NOMENCLATURE Catalyst of Au synthesised in-situ with a x wt% Au(xwt%)/support nominal gold content Catalyst of Au synthesised ex-situ with a x wt% ncAu(xwt%)/support nominal gold content ABREVIATIONS AFM Atomic Force Microscopy BE Binding Energy BET Brunauer-Emmett-Teller CB Carbon Black CN Coordination Number CNTs Carbon Nanotubes Co-P Co-Precipitation d Metal particle diameter DI Distilled water DOM Dimensionally Ordered Macroporous DP Deposition-Precipitation EXAFS Extended X-ray Absorption Fine Structure fcc face-centered cubic FT Fourier Transform HRTEM High Resolution Transmission Electron Microscopy ICP-OES Inductively Coupled Plasma-Optical Emission Spectroscopy MWCNTs Multiwalled Carbon Nanotubes NPs Nanoparticles SEM Scanning Electron Microscopy STEM Scanning Transmission Electron Microscopy SWCNTs Singlewalled Carbon Nanotubes T Temperature TEM Transmission Electron Microscopy TG Thermogravimetric TGA Thermogravimetric Analysis TPO Temperature Programmed Oxidation T50 Temperature at which 50% of the carbon material is converted Ti Initial temperature of combustion of the carbon material Temperature of the maximum combustion rate of the carbon T m material Temperature of the inflection point of the TG curve of the carbon T s material XANES X-ray Absorption Near Edge Structure XAS X-ray Absorption Spectroscopy INDEX SUMMARY .....................................................................................................................................1 CHAPTER 1: ..................................................................................................................................5 INTRODUCTION ..........................................................................................................................5 1.1 CATALYSIS BY GOLD.................................................................................................7 1.2 THE IMPORTANCE OF SMALL GOLD NANOPARTICLES (GOLD CLUSTERS) ...................................................................................................................8 1.2.1 GOLD NANOPARTICLES STRUCTURAL AND ELECTRONIC PROPERTIES DEPENDENCE ON THEIR SIZE ....................................... 10 1.2.2 METAL-SUPPORT INTERACTIONS .......................................................... 13 1.3 SYNTHESIS OF SUPPORTED Au NANOPARTICLES/NANOCLUSTERS .. 16 1.3.1 IMPREGNATION ............................................................................................. 18 1.3.2 CO-PRECIPITATION ...................................................................................... 20 1.3.3 DEPOSITION-PRECIPITATION .................................................................. 21 1.3.4 ANION ADSORPTION .................................................................................... 23 1.3.5 COLLOIDAL GOLD .......................................................................................... 23 1.3.6 SONOCHEMICAL SYNTHESIS ..................................................................... 25 1.3.7 OTHER METHODS.......................................................................................... 28 1.4 HETEROGENEOUS CATALYSIS WITH GOLD ATOMS (SYNTHESIS OF ISOLATED GOLD ATOMS) .................................................................................... 29 1.5 CATALYSTS SUPPORTS ......................................................................................... 31 1.6 GOLD CATALYSTS’ PRACTICAL APLICATIONS ............................................. 35 1.6.1 CO OXIDATION................................................................................................ 35 1.6.2 CATALYTIC OXIDATION OF CARBONACEOUS MATERIALS............ 41 1.8 OBJECTIVES .............................................................................................................. 57 1.9 REFERENCES ............................................................................................................ 59 CHAPTER 2: ............................................................................................................................... 71 CHARACTERISATION TECHNIQUES AND METHODS ................................................. 71 2.1 TRANSMISSION ELECTRON MICROSCOPY (TEM) ...................................... 73 i 2.2 SCANNING ELECTRON MICROSCOPY (SEM) ................................................. 76 2.3 ATOMIC FORCE MICROSCOPY (AFM) .............................................................. 77 2.4 X-RAY PHOTOELECTRON SPECTROSCOPY (XPS) ......................................