Ultrathin metal oxide layers have emerged in recent years as a powerful approach for substantially enhancing the performance of photo, electro, or thermal catalytic systems for energy, in some cases even enabling the use of highly attractive materials previously found unsuitable. This development is due to the confluence of new synthetic preparation methods for ultrathin oxide layers and a more advanced understanding of interfacial phenomena on the nano and atomic scale. This book brings together the fundamentals and applications of ultrathin oxide layers while highlighting connections and future opportunities with the intent of accelerating the use of these materials and techniques for new and emerging applications of catalysis for energy. It comprehensively covers the state-of-the-art synthetic methods of ultrathin oxide layers, their structural and functional characterization, and the broad range of applications in the field of catalysis for energy. Edited by leaders in the field, and with contributions from global experts, this title will be of interest to graduate students and researchers across materials science and chemistry who are interested in ultrathin oxide layers and their applications in solar energy conversion, renewable energy, photocatalysis, electrocatalysis and protective coatings.
Author(s): Heinz Frei, Daniel Esposito
Series: Energy and Environment Series
Publisher: Royal Society of Chemistry
Year: 2022
Language: English
Pages: 377
City: London
Cover
Contents
Chapter 1 Introduction
References
Chapter 2 Oxide Coatings for Semiconductor Light Absorbers: Advanced Synthesis and Applications
2.1 Context and Introduction
2.1.1 Silicon and III–V Photovoltaics and Photoelectrochemistry
2.1.2 Functionalities of Ultrathin Films in PV and PEC Devices
2.1.3 Why Oxides for These Applications?
2.2 Recent Developments in the Synthesis of Ultrathin Oxide Layers
2.2.1 Physical Vapor Deposition
2.2.2 Chemical Vapor and Atomic Layer Deposition
2.2.3 Wet Chemical Deposition and Substrate Oxidation
2.3 Case Studies of Thin Oxide Layers
2.3.1 Thin Oxide Protective Films for Semiconductor Photoelectrochemistry
2.3.2 Surface Passivation of Silicon
2.3.3 Selective Contact (Charge-extracting) Layers as Applied to Silicon
2.4 Future Outlook
Acknowledgements
References
Chapter 3 Ultrathin Oxides for Solar Cells
3.1 Passivation Layers
3.1.1 Function
3.1.2 Mechanisms
3.1.3 Examples
3.2 Contact Layers/Buffer Layers
3.2.1 Function
3.2.2 Mechanisms
3.2.3 Examples
3.3 Recombination Layers
3.3.1 Function
3.3.2 Mechanisms
3.3.3 Examples
3.4 Barrier Layers
3.4.1 Function
3.4.2 Mechanisms
3.4.3 Examples
3.5 Anti-reflection Coatings
3.5.1 Function
3.5.2 Mechanisms
3.5.3 Examples
3.6 Anti-soiling Coatings
3.6.1 Function
3.6.2 Mechanism
3.6.3 Examples and Emerging Applications
3.7 Opportunities and Challenges
3.7.1 Multifunctionality
3.7.2 Deposition Methods
3.7.3 Cost, Stability, and Circularity
3.7.4 Challenges for Specific Oxide Applications
References
Chapter 4 Blocking Layers for Controlling Directional Charge Transport in Dye-sensitized Photoelectrochemical Cells
4.1 Introduction
4.1.1 Photosynthesis
4.1.2 Dye-sensitized Solar Cells
4.1.3 Water-splitting Dye-sensitized Photoelectrochemical Cells
4.1.4 Core–Shell Architectures to Control Charge Transfer
4.2 Characterization
4.2.1 Materials Characterization
4.2.2 Transient Absorption Spectroscopy
4.2.3 Terahertz (THz) Spectroscopy
4.2.4 Electrochemical Methods
4.3 Electronic Structure
4.3.1 Insulating Layers for DSSCs
4.3.2 SnO Core–TiO2 Shell Architecture for WS-DSPECs
4.3.3 TiO2 Layers on Transparent Conducting Oxides
4.3.4 Electronic Structure of the SnO2 Core–ZrO2 Shell Architecture
4.4 Device Level Effects
4.4.1 Effects of Thin Oxide Layers on the Performance of DSSCs
4.4.2 Performance of Core–Shell Structures in WS-DSPECs
4.5 Conclusion and Outlook
References
Chapter 5 Performance Enhancement of TiO2-encapsulated Photoelectrodes Based on III–V Compound Semiconductors
5.1 Introduction
5.2 Fabrication, Characterization, and Surface States of TiO2 Layers
5.2.1 Fabrication Methods
5.2.2 Characterization Methods
5.2.3 Catalytic Outer Surface States
5.2.4 Quantifying Surface States
5.3 Photocatalytic Enhancement of TiO2encapsulated III–V Semiconductors
5.3.1 InP
5.3.2 GaP
5.3.3 GaAs
5.4 pH and Electrode Potential Stability Range
5.4.1 Pourbaix Diagram of Titanium
5.4.2 Limits of Pourbaix Diagrams
5.5 Outlook
Acknowledgements
References
Chapter 6 Metal Oxide Co-catalyst Nanolayers on Photoelectrodes
6.1 Introduction to Photoelectrochemical Water Oxidation
6.2 Light Absorbers and Metal Oxide Co-catalyst Nanolayers
6.2.1 The Semiconductor Photoanode and Co-catalyst Interface
6.2.2 Common Light-absorbing Photoanodes and Their Optical and Electronic Properties
6.2.3 Deposition of Metal Oxide Co-catalyst Nanolayers on Light Absorbers
6.2.4 Chemical Transformation of Metal Oxide Layers in Electrolytes
6.3 Dual Working Electrode Measurements on Composite Photoelectrode Thin Films
6.3.1 Experimental Setup of Dual Working Electrode (DWE) Measurements
6.3.2 Following Interfacial Charge Transfer Through Catalyst Thin Films with DWE Measurements
6.3.3 Impacts of Loading of Metal Oxide Catalysts
6.4 Electrochemical Atomic Force Microscopy Measurements on Nanostructures
6.4.1 Experimental Setup of Potential-sensing Electrochemical Atomic Force Microscopy Measurements
6.4.2 Interfacial Charge-transfer Measurements with PS-EC-AFM Measurements
6.4.3 Influence of Catalyst Loading on Metal Oxides
6.4.4 Spatially Resolved Photovoltages of Si with Ni(Fe)-based Oxide Nanoparticle Catalysts
6.5 Conclusion
6.6 Outlook
Acknowledgements
References
Chapter 7 Design Principles for Oxideencapsulated Electrocatalysts
7.1 Introduction
7.2 Species Transport Through Oxide Overlayers
7.2.1 Transport Fundamentals
7.2.2 Mass Transfer-limited Current Densities
7.2.3 Concentration Overpotentials
7.2.4 Transport Through Non-ideal Overlayers
7.3 Influence of Overlayers on Reaction Kinetics
7.3.1 Combining Transport and Kinetic Losses in OECs
7.3.2 Transport-mediated Reaction Selectivity
7.3.3 Confinement Effects on Electrocatalysis at Buried Interfaces
7.4 Influence of Oxide Overlayers on Electrocatalyst Stability
7.4.1 Mechanisms for Stability Enhancement by Encapsulation
7.4.2 Adhesion and Geometric Considerations for OEC Stability
7.5 Experimental Methods for Assessing the Performance of OECs
7.5.1 Preparation of OECs
7.5.2 Characterizing the ECSA of OEC Electrodes
7.5.3 Deconvoluting Transport Effects from Kinetic Effects
7.5.4 Stability Tests
7.6 Outlook: Challenges and Opportunities for OECs
Acknowledgements
References
Chapter 8 Synthesis Techniques for Ultrathin Oxide Layers of Heterogeneous Catalysts
8.1 Introduction
8.1.1 Heterogeneous Catalysis
8.1.2 Catalyst Deactivation
8.2 Synthesis Techniques for Encapsulating Metal Nanoparticle Catalysts
8.2.1 Encapsulation of Metal Nanoparticles Using Zeolites
8.2.2 Encapsulation of Metal Nanoparticles Using Oxide Shells
8.3 Encapsulation of Heterogeneous Catalysts Using Atomic Layer Deposition (ALD)
8.3.1 Introduction to ALD
8.3.2 ALD Tools and Methods for Coating Particles
8.3.3 ALD Coating to Enhance Catalytic Performance
8.4 Conclusions and Perspective
References
Chapter 9 Ultrathin Oxide Coatings Synthesized Via Wet Chemical Processes for Electrocatalytic Systems
9.1 Introduction
9.2 Ultrathin Metal Oxide Coatings from Sol–Gel Deposition Processes
9.2.1 Sol–Gel Process
9.2.2 Ultrathin Metal Oxide Coatings from Sol–Gel Processes
9.2.3 Sol–Gel Metal Oxide Nanocoatings as Electrocatalyst Supports
9.3 Metal Oxide Nanocoatings from Condensed Layer Deposition
9.3.1 The Condensed Layer Deposition Process
9.3.2 Metal Oxide Nanocoatings from Condensed Layer Deposition
9.3.3 Nanocoatings from CLD for Electrocatalytic Systems
9.4 Conclusions and Outlook
References
Chapter 10 Applications of Metal Oxide Layers on Particulate Photocatalysts for Water Splitting
10.1 Introduction
10.2 Suppression of Back Reactions on Co-catalysts and Photocatalysts
10.2.1 NiO on Ni to Suppress Back Reactions
10.2.2 Cr2O3 on Metal/Metal Oxide Co-catalysts
10.2.3 Amorphous TiO2 (a-TiO2) Layers on Photocatalysts
10.2.4 Other Oxide Layers
10.3 Improved Photocatalyst Hydrophilicity
10.3.1 Hydrophilic MgO Nanolayers on Ta3N5 to Improve H2 and O2 Evolution
10.3.2 Porous Hydrophilic SiO2 Layers on LaMg1/
for Improving Water Splitting Activity
10.4 Passivation of the Oxynitride Surface by ZrO2
10.5 Control Over the Redox Selectivity of Photocatalysts in Z-scheme Water Splitting
10.5.1 Rutile-type TiO2 and MgO in Z-scheme Systems Containing IO3
/I
10.5.2 CeOx on O2 Evolution Co-catalysts
10.6 Protection of Photocatalysts and Photoelectrodes by a TiO2 Layer
10.6.1 Photocatalysts
10.6.2 Photocathodes
10.6.3 Photoanodes
10.7 Outlook
10.7.1 Suppression of Back Reactions on the Surface Under Ambient Pressure
10.7.2 Facilitation of the Mass Transport of H2 and O2 as Products
10.7.3 Suppression of Interfacial Charge Recombination Between a Photocatalyst and a Co-catalyst
10.7.4 Enhancement of Charge Separation
10.7.5 Alteration of the Band Edge Position
References
Chapter 11 Ultrathin Silica Layers as Separation Membranes for Artificial Photosynthesis
11.1 Introduction
11.2 Design Concept
11.3 Charge-conducting Molecular Wires with Tunable Energetics
11.3.1 Wire Assembly and Tuning of Energetics
11.3.2 Structure and Orientation of Anchored Molecular Wires by Polarized FT-IRRAS
11.4 Fabrication of Membranes in Planar and Nanotube Assemblies
11.4.1 Planar Samples for Photoelectrochemical Characterization
11.4.2 Core–Shell Nanotube Arrays for Photocatalytic Evaluation
11.5 Charge Transport Through an SiO2 Membrane
11.5.1 Short-circuit Photocurrent Measurements
11.5.2 Ultrafast Optical Spectroscopy
11.6 Proton Transport Through Membranes
11.6.1 Monitoring the Proton Flux Across SiO2 Nanolayers
Via FT-IRRAS Isotope Tracing
11.6.2 Electrochemical Characterization of Proton Flux and O2 Impermeability of Single SiO2 Nanolayers
11.6.3 Electrochemical Characterization of Proton Flux of
Single Co3O4 and TiO2 Nanolayers and Multi-oxide
Stacked Nanolayers
11.7 Photocatalysis Under Ultrathin Membrane Separation
11.8 Outlook
Acknowledgements
References
Chapter 12 Outlook
12.1 Introduction
12.2 Challenges and Opportunities for Modeling Ultrathin Oxides
12.3 Spectroscopic Tools for Probing Buried Interfaces
12.4 Temporally Resolved Dynamics of Processes at Interfaces
Acknowledgements
References
Subject Index
