Modification Strategy Of Semiconductor Photoanode For Catalytic Water Oxidation

The shortage of fossil fuels and global warming have become very serious social and environmental problems.Hydrogen is a kind of clean energy with high heating value.Therefore,how to use solar energy to produce hydrogen has been attracted widespread attention.Building a photoelectrochemical cell(PEC)to mimic the photosynthesis system is an effective method to realize the conversion of solar energy into hydrogen energy.In the photoelectrochemical system,the water oxidation reaction involves the transfer of multiple electrons and protons,which is the main factor restricting the development of photoelectrochemical cells.Therefore,designing and developing high-efficiency photoanode to construct photoelectrochemical cell is the key to realize solar energy to produce hydrogen.In this paper,several semiconductor materials were used to prepare photoanodes.Different strategies were explored for PEC water splitting.The specific works are as follows:1.Constructing TaON/BiVO₄heterojunction photoanode by simple hydrothermal method.TaON/BiVO₄heterojunction photoanode can promote the separation and transfer of photogenerated electron-hole pairs,and exhibit high photoelectric catalytic water oxidation activity.Under simulated solar irradiation(AM 1.5 G,100 m W/cm²)with a bias of 1.23 V vs.RHE,the electrochemical performance tests show that the photocurrent of the 2-TaON/BiVO₄electrode reaches to 2.6 m A/cm²,which is 1.75 times that of the bare BiVO₄electrode.In order to enhance the surface water oxidation kinetics of the photoanode,the Co-Pi water oxidation cocatalyst is immobilized on the photoanode and the PEC performance is further promoted.A high photocurrent density of 3.6 m A/cm²is achieved.2.Using Au nanoparticles and molecular catalyst to modify the BiVO₄photoanode.A functional three-component photoanode Co F16Pc/Au/BiVO₄was constructed.For the plasmon effect of Au nanoparticles and the interaction with molecular catalyst,the photoelectric catalytic effect of the three-component photoanode Co F16Pc/Au/BiVO₄is significantly better than that of the two-component photoanodes Au/BiVO₄and Co F16Pc/BiVO₄.Under simulated solar irradiation(AM 1.5 G,100 m W/cm²)with a bias of 1.23 V vs.RHE,the photocurrent density of the Co F16Pc/Au/BiVO₄photoanode reaches to 4.2 m A/cm²,which is 3 times that of the bare BiVO₄electrode.3.TaON photoanodes were prepared and modified with TiO₂and TaCl₅respectively.The molecular catalyst[Ir(pyalc)(H₂O)₂(?-O)]₂²⁺was synthesized as a cocatalyst for the photocatalytic water oxidation system.when the Ir cocatalyst was immobilized on the photoanode,the electrochemical performance test results show that the photocurrent density of each composite photoanode is significantly increased.After comparison,the photocurrent density and photoelectric catalytic water oxidation effect of Ir+NH₃+TaCl₅/TaON photoanode is the best.Under simulated solar irradiation(AM 1.5G,100 m W/cm²)with a bias of 1.23 V vs.RHE,the photocurrent density reaches to 84?A/cm².4.GaN-ZnO,TiO₂/GaN-ZnO photoanodes were fabricated.The cocatalyst FeOOH was deposited on the surface of the GaN-ZnO photoanode to improve the water oxidation performance.Under simulated solar irradiation(AM 1.5 G,300 m W/cm²),with a bias of1.23 V vs.RHE,the photocurrent density of FeOOH/TiO₂/GaN-ZnO photoanode increased to 178?A/cm²,which is 25 times that of the bare GaN-ZnO photoanode.