Metal-Semiconductor Hybrid Nanomaterials: Design, Fabrication And Application In Solar Water Splitting

To address the quick growing of the world's energy demands and the serious environmental crisis caused by the consumption of fossil fuels,developing the abundant,clean and renewable energy has been attracted considerable interest in worldwide.For the numerous new energy,hydrogen?H2?with the advantages such as high efficiency,zero-carbon emission,safety and recyclability has been regarded as one the most promising new energy in the 21st century.In industry,the production of H2 is currently based on electrolysis of water,water-gas shift reaction and the steam methane reforming,energy intensive processes with huge drain of electric power or fossil fuel,which can not solve the energy crisis and environmental pollution problems fundamentally.Solar energy is the most abundant,renewable and clean energy,making effective use of solar energy has great significance to solve the energy crisis.Hydrogen production from water splitting driven by sunlight based on semiconductor materials serves as one of the most promising pathway for converting solar energy to chemical energy.To achieve high solar energy conversion efficiency,semiconductor materials is the key factor.Ideally,the photocatalyst should have strong absorption of solar light,efficient charge separation and transport properties,and suitable redox and oxidation potentials for water splitting.Despite many processes have been made,the efforts invested to well fulfil the commercial requirement for water splitting have been far less successful in past decades.However,nanostructure,combination and modification of semiconductor materials are possible to break through this limit.The work of this paper is mainly focusing on the fabrication of metal-semiconductor nanocomposite materials and exploring their application in the field of solar water splitting.The hydrothermal method,ultrasonic reduction method,self-assembly method,atomic layer deposition method and thermal vapor condensation methods has been used to prepare and construct a series of metal-semiconductor nanomaterials with novel structure and excellent performance for water splitting.The main research content includes the following several aspects.In the second chapter,the three-dimensional?3D?urchins-like ZnO with a unique micro/nano heterostructure consists multi-nanorods has been synthesized through hydrothermal.The Au nanoparticles?NPs?were reduced on the nanorods by ultrasonicing the HAuCl4 precursor in blend of ethanol and water to fabricate the 3D urchins-like ZnO/Au.In the third chapter,we report a highly active all-solid-state Z-scheme PS-C-PS photo cathode for enhanced PEC H2 evolution by introducing a 3D urchins-like ZnO/Au/graphitic carbon nitride?g-C₃N₄?semiconductor-metal-semiconductor heterostructure.The ternary Z-scheme ZnO/Au/graphitic carbon nitride?g-C₃N₄?composite photocatalyst has been applied as a photocathode in a photoelerochemical?PEC?cell for H2 evolution,exhibiting excellent performance.With a bias of 0 V vs.RHE in neutral electrolyte,the Z-scheme ZnO/Au/g-C₃N₄ photocathode shows a constant H2 production rate of 3.69 ?mol h-1 cm-2 and a remarkable Faradaic efficiency of 95.2%.The PEC reaction mechanism of the urchins-like ZnO/Au/g-C₃N₄ photocathode has been discussed.In the forth chapter,we describe the fabrication of Au@Ag nanorods?NRs?sensitized TiO₂ nanowires?NWs?on F-doped SnO2?FTO?substrates by an hydrothermal growth and subsequent self-assemble method.The enhanced photocurrent of Au@Ag NRs/TiO₂ NWs photoanode is attributed to the local surface plasmon resonance effect of Au@Ag nanorods.The performance of metal-semiconductor nanomaterials in solar energy capture,light charge-carrier separation and transport and water splitting were systematically investigated through characterization analysis of the material structure,component,optical properties,electrochemical and catalytic activity.This work provides new ideas and methods for the next commercial application prospect of semiconductor materials with efficient water splitting performance.