Surface Modification/Passivation Of Bismuth Vanadate Electrode Materials And Study On Its Photoelectric Water Decomposition Performance

Under the national goal of"carbon peaking and carbon neutralization",hydrogen with high energy density,cleanness and regeneration has attracted much attention because of its important role in carbon reduction.Solar driven photoelectrochemical（PEC）water decomposition realizes the water hydrogen water cycle in a zero-emission manner,and is considered a promising strategy to alleviate energy and environmental problems.Bismuth monoclinic vanadate（BiVO₄）has an appropriate optical capture band gap and energy band structure,so it has a great application prospect.However,the photocurrent density of BiVO₄ is significantly below its theoretical limit(7.5 m A cm^-2,AM 1.5 G)due to the unfavorable water oxidation kinetics and internal and external charge carrier recombination.In order to solve the above problems,the following research has been done in this paper to reduce interface electron hole recombination,improve charge separation efficiency,and prepare high-performance BiVO₄ photoanodes:1.The introduction of Cl^-（3.16）with appropriate electronegativity into BiVO₄surface polarization by simple solution immersion method is helpful to capture photogenerated holes and prolong the electron lifetime.The photocurrent of Cl-BiVO₄reaches 2.55 m A cm^-2（1.23 V vs RHE）.Then,the high-performance composite photoanode Ni（OH）₂/Cl-BiVO₄ was successfully prepared by loading the co-catalyst Ni（OH）₂ on Cl-BiVO₄.It shows a photocurrent density of 4.33 m A cm^-2（1.23 V vs RHE）,which is 3.0 times higher than BiVO₄(1.44 m A cm^-2).In addition,the negative initial potential shift,applied bias photon-to-current efficiency（ABPE）,incident photon-to-current efficiency（IPCE）and charge separation efficiency are also significantly improved.This study provides a simple and effective strategy for the production of low-cost,high-performance solar water decomposition catalyst.2.On the basis of the above work,we designed an experiment to explore the charge transfer at the interface of semiconductor-electrolyte using the water oxidation bimetallic co-catalyst Fe_xCo_1-xOOH,which promoted the universality of Cl^-modification for improving the performance of PEC.The coupling of Cl-BiVO₄ and the cocatalyst with bimetallic active sites shows a higher photocurrent LSV curve(4.63 m A cm^-2,1.23 V vs RHE)and a lower initial potential,which promotes the charge carrier transport and surface OER reaction.3.An ultrathin MgO passivation layer was introduced into the Co₂AlO₄/BiVO₄coupling system by electrodeposition,and a ternary composite photoanode Co₂AlO₄/MgO/BiVO₄ was constructed.Its photocurrent density(1.23 V vs RHE,3.52m A cm^-2)is 3.2 times higher than that of pure BiVO₄,and its optical absorption,IPCE,ABPE,etc.have been significantly improved.Theoretical calculations show that MgO promotes the migration of electrons to the BiVO₄ layer and drives effective hole transport,thus inhibiting the rapid electron hole recombination at the Co₂AlO₄/BiVO₄ interface.Therefore,the catalytic activity and water oxidation kinetics of the system have been significantly improved.