The Photoelectrochemical Performance For Water Splitting Of The Novel Photoanodes Based On Bismuth Vanadate

With the continuous development of human society,the demand for energy is increasing day by day.The fossil energy has played an important role in human society.However,the global reserves of fossil energy is declining,owing to the continuous exploitation and there is an urgent need to find alternative renewable energy sources.As an inexhaustible source of clean energy,solar energy has gradually attracted people's attention.It is an effective way to convert solar energy into chemicalenergybyphotoelectrochemicaltechnique.However,ina photoelectrochemical water splitting system,each molecule of oxygen generated need to transfer 4 electrons,which will increase the potential barrier and resistance of the reaction.Therefore,the fabrication of a highly efficient photoanode has become popular.Semiconductor materials are widely used in photoelectrocehnmical water splitting system due to their good light absorption properties and suitable band positions.However,the shortcomings of semiconductor,such as the fast return rate of photogenerated electrons and holes,and the poor surface dynamics limit its development.In this paper,the TiO₂/BiVO₄ composite photoanode was fabricated by hydrothermal method to improve the separation of photogenerated charge.In this system,bismuth vanadate mainly plays the role of light absorption.The titanium dioxide nanospheres was introduce to form heterojunctions with bismuth vanadate,leading to a improved separation of electrons and holes.The PEC test results demonstrate that the TiO₂/BiVO₄ photoanodes show a highwater oxidation photocurrent density of 3.2 mA/cm²at 1.23 V_RHE,which significantly exceeds that of the related heterojunctions reported in the literature.Finally,the molecular catalyst was modified on the composite photoanode,a further increase in photocurrent density was obtained,reaching 4.6 mA/cm²at 1.23 V_RHE.Secondly,the pristine semiconductors presenta weak surface dynamic in PEC water splitting.Therefore,a novel method of supporting the water oxidation catalyst is designed in this work to improve the dynamic performance of the electrode.The cobalt cubane was immobilized onto the bismuth vanadate electrode by electropolymerization.The resulting photoanode fabricated by electropolymerization show high PEC performance for water splitting.After the introduction of vinyl phosphoric acid on the surface of bismuth vanadate,the catalyst molecule can be covalently bonded to the surface of the electrode.The prepared electrodes show a significant improvement both in PEC activity and stability.In order to improve the utilization of holes in semiconductor/molecular catalyst photocatalysts.In this paper,gold nanoparticles were introduced on the surface of bismuth vanadate semiconductor electrodes.Because of the surface plasmon resonance effect of gold under illumination,a large number of hot holes were generated,which enriched the holes on the gold nanoparticles.By targeting modification of molecular catalysts,the catalyst molecules can be adsorbed on gold nanoparticles,which increases the utilization of generated holes.The PEC performance of the composite electrode was obviously improved,with a high photocurrent density of 4.5 mA/cm²(1.23 V_RHE),which provides a design idea for the preparation of a highly efficient photoanode in the future.