Electrochemistry of Metal Chalcogenides Monographs in Electrochemistry

Surprisingly, a large number of important topics in electrochemistry is not covered by up-to-date monographs and series on the market, some topics are even not covered at all. The series Monographs in Electrochemistry fills this gap by publishing indepth monographs written by experienced and distinguished electrochemists, cov- ering both theory and applications. The focus is set on existing as well as emerging methods for researchers, engineers, and practitioners active in the many and often interdisciplinary fields, where electrochemistry plays a key role. These fields will range Ð among others Ð from analytical and environmental sciences to sensors, materials sciences and biochemical research. Information about published and forthcoming volumes is available at http://www.springer.com/series/7386 Series Editor: Fritz Scholz, University of Greifswald, Germany Mirtat Bouroushian

Electrochemistry of Metal Chalcogenides

123 Dr. Mirtat Bouroushian National Technical University of Athens Dept. of Chemical Sciences School of Chemical Engineering Heroon Polytechniou Str. 9 Zographos Campus 157 73 Athens Greece [email protected]

ISBN 978-3-642-03966-9 e-ISBN 978-3-642-03967-6 DOI 10.1007/978-3-642-03967-6 Springer Heidelberg Dordrecht London New York

Library of Congress Control Number: 2009943933

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Springer is part of Springer Science+Business Media (www.springer.com) Preface

This monograph is devoted to the electrochemistry of metal chalcogenides, a group of chemical compounds which possess very interesting properties for applications in various areas, e.g., electronics and optics, ion-sensitive electrodes, solar energy harvesting, fuel cells, catalysis, and passivation. The role which electrochemistry plays in studies of metal chalcogenides is twofold: on one side it is a synthesis tool and on the other side it can be utilized for the characterization and analysis of these compounds. It is thus a basic requirement that the fundamentals of electrochemical thermodynamics and kinetics of these systems are thoroughly studied and docu- mented. The author Mirtat Bouroushian from the National Technical University of Athens must be given full credit for presenting the ﬁrst book completely devoted to the electrochemistry of metal chalcogenides, a research topic to which he has made numerous own contributions. This monograph gives a well-balanced description of the properties of chalcogens and their major chemical compounds together with the state-of-the-art electrochemical synthesis of various metal chalcogenide phases and their characterization, as well as an account of the wide range of applications. Everybody who works with metal chalcogenides, and of course especially anybody dealing with the electrochemistry of these compounds, will ﬁnd this monograph a very rich source of carefully and critically compiled information. I am sure that industrial electrochemists and researchers in institutes and universities as well as graduate students of material science, physics, electronics, and chemistry will highly appreciate to have this monograph at hands during their daily work.

January 2010 Fritz Scholz EditoroftheseriesMonographs in Electrochemistry

Contents

1 Chalcogens and Metal Chalcogenides ...... 1 1.1 The Chalcogens ...... 1 1.1.1 History and Occurrence ...... 2 1.1.2 Production and Uses ...... 4 1.1.3AllotropyÐStatesofMatter...... 7 1.1.4 Chemical Properties and Compounds ...... 10 1.1.4.1 Hydrides...... 12 1.1.4.2 Oxides and Oxoacids ...... 12 1.1.4.3 Thio- and Seleno-sulfates ...... 14 1.1.4.4 Polychalcogenide Ions ...... 15 1.2 The Metal Chalcogenides ...... 16 1.2.1Solids,Complexes,andClusters...... 16 1.2.2CommonSolidStructures...... 19 1.2.3 Ternary Compounds and Alloys ...... 22 1.2.4 Intercalation Phases ...... 24 1.2.5 Chalcogenide Glasses ...... 24 1.2.6 Materials Synthesis ...... 25 1.2.7 An Account of the Periodic Table ...... 28 1.2.7.1 Group IA (1). Lithium, Sodium, Potassium,Rubidium,Cesium...... 28 1.2.7.2 Group IIA (2). Beryllium, Magnesium, Calcium,Strontium,Barium...... 29 1.2.7.3 Group IIIA (3). Scandium, Yttrium, Lanthanoids, Actinoids ...... 29 1.2.7.4 Group IVA (4). Titanium, Zirconium, Hafnium 32 1.2.7.5 Group VA (5). Vanadium, Niobium, Tantalum . 33 1.2.7.6 Group VIA (6). Chromium, Molybdenum, Tungsten ...... 35 1.2.7.7 Group VIIA (7). Manganese, Technetium, Rhenium ...... 37 1.2.7.8 Group VIII (8Ð10). Iron, Cobalt, Nickel .... 38

vii viii Contents

1.2.7.9 Group VIII (8Ð10). Platinum Group Metals(Ru,Os,Rh,Ir,Pd,Pt)...... 40 1.2.7.10 Group IB (11). Copper, Silver, Gold ...... 41 1.2.7.11 Group IIB (12). Zinc, Cadmium, Mercury . . . 45 1.2.7.12 Group IIIB (13). Boron, Aluminum, Gallium, Indium, Thallium ...... 48 1.2.7.13GroupIVB(14).Germanium,Tin,Lead.... 49 1.2.7.14GroupVB(15).Antimony,Bismuth...... 51 General References ...... 52 References ...... 52

2 Electrochemistry of the Chalcogens ...... 57 2.1 General References ...... 57 2.1.1 Tables of Aqueous Standard and Formal Potentials .... 59 2.1.2 Pourbaix Diagram for SulfurÐWater ...... 62 2.1.3 Pourbaix Diagram for SeleniumÐWater ...... 64 2.1.4 Pourbaix Diagram for TelluriumÐWater ...... 65 2.2 General Discussion ...... 67 2.2.1Sulfur...... 67 2.2.2Selenium...... 69 2.2.3Tellurium...... 71 References ...... 73

3 Electrochemical Preparations I (Conventional Coatings and Structures) ...... 77 3.1BasicPrinciplesandIllustrations...... 77 3.1.1 Cathodic Electrodeposition ...... 78 3.1.2 Anodization and Other Techniques ...... 84 3.1.3 Pourbaix Diagrams ...... 85 3.1.4NucleationandGrowth...... 86 3.2 Binary Compounds and Related Ternaries ...... 88 3.2.1CadmiumSulﬁde(CdS)...... 88 3.2.2 Cadmium Selenide (CdSe) ...... 94 3.2.3CadmiumTelluride(CdTe)...... 98 3.2.4ZincSulﬁde(ZnS)...... 103 3.2.5 Zinc Selenide (ZnSe) ...... 104 3.2.6ZincTelluride(ZnTe)...... 105 3.2.7 Mercury Chalcogenides ...... 106 3.2.8 Pseudobinary IIÐVIxÐVI1−x and II1−xÐIIxÐVI Phases . . 106 3.2.9 Molybdenum and Tungsten Chalcogenides ...... 110 3.2.10 Copper Chalcogenides ...... 112 3.2.11 Silver Chalcogenides ...... 113 3.2.12 Indium Chalcogenides ...... 114 3.2.13 CopperÐIndium Dichalcogenides ...... 115 3.2.14 Manganese and Rhenium Chalcogenides ...... 119 Contents ix

3.2.15 Iron Chalcogenides ...... 120 3.2.16 Tin Chalcogenides ...... 121 3.2.17 Lead Chalcogenides ...... 124 3.2.18 Bismuth and Antimony Chalcogenides ...... 128 3.2.19 Rare Earth Chalcogenides ...... 131 3.3 Addendum ...... 132 3.3.1 Chemical Bath Deposition ...... 132 3.3.2 Electrodeposited CdTe Solar Cells ...... 137 References ...... 139

4 Electrochemical Preparations II (Non-conventional) ...... 153 4.1 General ...... 153 4.2 Epitaxial Films and Superstructures ...... 154 4.2.1 Single-Step Epitaxy on Semiconductor Substrates .... 155 4.2.2 Electrochemical Atomic Layer Epitaxy ...... 162 4.2.3 SuperstructuresÐMultilayers ...... 169 4.3 Atomic Layer Epitaxy and UPD Revisited ...... 172 4.4 Electrodeposition of Nanostructures: Size-Quantized Films on Metal Substrates ...... 182 4.5DirectedElectrosynthesis...... 187 4.5.1PorousTemplates...... 189 4.5.2 Templated and Free-Standing Nanowires and otherForms...... 191 4.5.3 Electrochemical Step Edge Decoration ...... 196 References ...... 198 5 Photoelectrochemistry and Applications ...... 207 5.1 General ...... 207 5.2 Photoelectrochemical Properties ...... 209 5.2.1 Redox and Surface Chemistry vs. Electrode Decomposition 210 5.2.2EnergeticConsiderations...... 213 5.2.3 Cadmium Chalcogenides ...... 216 5.2.3.1 Single-Crystal Photoelectrodes Ð PEC Fabrication and Properties ...... 216 5.2.3.2 Single-Crystal Photoelectrodes Ð A Closer Look into Interfacial Electrochemistry ...... 223 5.2.3.3 Polycrystalline Photoelectrodes ...... 229 5.2.4 A Note on Multilayer Structures ...... 233 5.2.5 Zinc Chalcogenides ...... 235 5.2.6 Layered Transition Metal Chalcogenides ...... 238 5.2.6.1 SurfaceAnisotropyEffect...... 247 5.2.7 Iron Sulﬁdes ...... 248 5.2.8Chalcopyrites...... 251 x Contents

5.2.9 Some Chalcogenides of p-Block Metals ...... 255 5.2.9.1 Gallium and Indium Chalcogenides ...... 256 5.2.9.2 Tin Sulfides ...... 259 5.2.9.3 Lead Chalcogenides ...... 261 5.2.9.4 BismuthSulfide...... 262 5.3 Semiconductor Photocatalysis ...... 263 5.3.1ColloidalSystems...... 265 5.3.2 Solar Detoxification Ð CO2 Photoreduction ...... 268 5.3.3 Photocatalytic Decomposition of Water ...... 270 5.3.3.1 Cadmium Sulfide and Related Photocatalysts . 275 5.3.3.2 Transition Metal Dichalcogenides and Related Photocatalysts ...... 279 5.4 Sensitized Solar Cells ...... 283 References ...... 292

6 Electrochemical Processes and Technology ...... 309 6.1 Oxygen Reduction Reaction Ð ORR ...... 309 6.1.1 General ...... 309 6.1.2 Pt-Free Chalcogenide Catalysts ...... 311 6.1.3 Methanol Oxidation ...... 317 6.1.4 ODP Applications (Oxygen-Depolarized ElectrolysisofHCl)...... 320 6.2 Electrochemical Energy Storage ...... 322 6.2.1 Intercalation in Chalcogenides ...... 322 6.2.2 Principles of the (Thin Film) Rechargeable LithiumBattery...... 324 6.2.3 Chalcogenide Cathodes for Rechargeable Lithium Cells . 326 6.2.4Mg-IonIntercalation...... 329 6.2.5 High-Power Batteries and Related Types ...... 330 6.2.5.1 Sulfur-based Cathode ...... 330 6.2.5.2 Se- and Te-based Cathodes ...... 334 6.2.5.3 ThermalBatteries...... 335 6.3 Ion-Selective Electrodes ...... 335 6.3.1 Chalcogenide Glass Sensors ...... 337 6.3.2Biosensors...... 339 References ...... 342 About the Editor ...... 351 About the Author ...... 353 Index ...... 355 Introduction

Metal chalcogenide (MCh) materials range from common oxides and sulfides, selenides, and tellurides, to complex compound or solid solution systems contain- ing different metal or chalcogen elements in various oxidation states and varying proportions. Owing to their wide spectrum of properties, these materials relate to a large variety of existing and potential applications in electronics, optics, magnetics, solar energy conversion, catalysis, passivation, ion sensing, batteries, and fuel cells. The present monograph aims for a systematic presentation of metal chalcogenides and the electrochemical material science relevant to this family of compounds. More than an introduction and less than a handbook, it is an attempt to give a comprehensive coverage of achievements, complications, and prospects in this area. This book regards in particular the systems relevant to the sulfur sub-group elements, i.e., sulfur, selenium, and tellurium. The reasons for this approach are fairly obvious. The metal compounds of the heavier congeners of oxygen, especially those of selenium and tellurium, are notably less known and not systematically studied compared to the corresponding oxides (and also to other inorganic compounds like halogenides). Thus, the need arises to fill this gap, which, aside from the nor- mal pace, is stimulated further by the unprecedented advancements that have been encountered in the chemistry and technology of these materials in the last decades. Adoption of this approach appears to be reasonable also in view of the immense breadth of the surveyed field and its multidisciplinary character: the common binary MCh compounds alone, excluding the oxides as well as the compounds of actinides and lanthanides, are more than a hundred, and it is rather difficult to contemplate the number of multielement combinations. The role of electrochemistry in synthesis, development, and characterization of the MCh materials and related devices is vital and of increasing importance, although it remains uncharted as to its content and borders. Electrochemistry as a preparation tool offers the advantages of soft chemistry to access bulk, thin film, and epitaxial growth of a wide range of alloys and compounds, while as a characterization tool provides exceptional assistance in specifying the physicochemical properties of materials. Moreover, quite important applications and modern devices base their operation on electrochemical principles. Thereupon, our scope in the first place was to organize existing facts on the electrochemistry of metal chalcogenides

xi xii Introduction regarding their synthesis, properties, and applications. In parallel, we hope to pro- vide an outlook of the field that opens up for the electrochemist or material scientist to explore, considering that not only have a lot of technologically interesting MChs not yet been the object of electrochemical investigation, but also numerous systems are completely unknown from this point of view. This book is designed as follows: The fundamentals of chalcogen chemistry and their compounds are presented in the first chapter where also a brief, though systematic, description is attempted of the metal chalcogenide solids on the basis of the Periodic Table, in terms of their structure and key properties. A general discussion on the electrochemistry of the chalcogens is the subject of the second chapter, where the basic equilibrium data are also provided for the aqueous chalcogen systems. Available facts and inferences regarding conventional films and novel structures of MChs prepared via the electrochemical route are illustrated in Chaps. 3 and 4, fol- lowing an introduction to the principles underlying the electrochemical formation of inorganic compounds and alloys, along with an outline of relevant preparation procedures. Insights into the fundamentals of photoelectrochemistry and research results sorted either from a material-oriented point of view or by the aspect of important light-induced processes constitute the subject matter of Chap. 5. Finally, topics on catalysis, mainly related to fuel cells, intercalation electrodes, batteries, and ion-sensing applications are introduced and discussed in Chap. 6. For realizing this monograph, I am deeply indebted to the Editor, Professor Fritz Scholz who first suggested the idea and vigorously sustained the project in every way with great enthusiasm. I also thank Dr. T. Kosanovic (NTUA) and greatly acknowledge her contribution to data collection and figure editing. Finally, special thanks are due to D. Vasilakopoulos (NTUA) for his continual support. Mirtat Bouroushian