Study On Co-catalyst Selection And Oxidation Performance In Photoanode

Photocatalytic（PEC）water splitting is a promising hydrogen production technology that involves the oxidation of water to produce oxygen on the photoanode and reducing water to produce hydrogen on the cathode.In theory,the co-catalyst modification on the surface of the photoanode can improve the carrier separation and oxygen evolution kinetics on the surface of the photoanod,but the co-catalyst modification can not always improve the performance of the photoanode in practice.In order to further understand the process of photogenerated carrier separation and surface reaction in PEC water splitting system,the influence of photochemical environment on the photoanode carrier separation and injection ability was discussed.Cobalt-based polyoxometalate（POMs）was modified on TiO₂surface.Cobalt in cobalt-based POMs can be oxidized by holes to produce high-priced cobalt,improving hole transport efficiency.Excessive water oxidation potential on the surface of BiVO₄photoanode.By modifying layered bimetallic hydroxides（LDHs）on the surface of BiVO₄,the oxidation reaction of alcohols replaces the oxidation reaction of water,which improves the hydrogen evolution efficiency while producing organic products.The specific contents are as follows:（1）Study on the influence of photochemical environment on photocatalytic reaction systemThe influence of photochemical environment on the photocatalytic reaction system was discussed by using TiO₂,BiVO₄and Fe₂O₃photoanodes.The photocurrent densities of TiO₂is simialr under back-side and front-side illumination.BiVO₄has better performance under back illumination while Fe₂O₃has better performance under front illumination.The photocurrent density of TiO₂in the electrolyte of p H=7 and p H=13 is similar,while the photocurrent density of Fe₂O₃in p H=13 is significiantly high than that in p H=7.It is found that the p H of electrolyte mainly affects the carrier injection efficiency.（2）Study on photocatalytic performance of TiO₂/Pd₁₂Co Se₈photoanode for water splittingTiO₂/Pd₁₂Co Se₈photoanode was prepared by electrostatic adsorption of Pd₁₂Co Se₈on TiO₂.The photocurrent density of TiO₂/Pd₁₂Co Se₈reached 1.78 m A cm^-2at 0.6 V vs.SCE,which is 1.24 times higher than that of TiO₂.Further studies on its showed that,compared with TiO₂,charge separation efficiency and injection efficiency of TiO₂/Pd₁₂Co Se₈increased by 10.27%and 24.15%,respectively.In the reaction process,the hole oxidizes Co ^IIin Pd₁₂Co Se₈to Co ^IIIand the high-valence Co ^IIIoxidizes water to produce oxygen.Pd₁₂Co Se₈improves the oxygen generation kinetics and promotes the separation and migration of photogenerated carriers.（3）Study on the photoanodic oxidation of glycerol by BiVO₄/LDHsBiVO₄/Ni Fe-LDH and BiVO₄/Ni Co-LDH photoanodes were synthesized by electrodeposition LDHs on BiVO₄.Compared with BiVO₄,the photocurrent densities enhancement of PEC water splitting for BiVO₄/Ni Co-LDH and BiVO₄/Ni Fe-LDH is similar.However,the photocurrent densities increment of BiVO₄/Ni Co-LDH in PEC glycerol oxidation system is 2.19 times that of BiVO₄/Ni Fe-LDH.The rate of BiVO₄/Ni Co-LDH oxidizing glycerol to DHA was 265μmol cm^-2h^-1,which was twice that of BiVO₄.The electrocatalytic results show that Ni Co-LDH is a better catalyst for glycerol oxidation than Ni Fe-LDH.Compared with Ni Fe-LDH,Ni Co-LDH can oxidize glycerol with higher dynamics to realize efficient utilization of holes.Therefore,BiVO₄/Ni Co-LDH has higher DHA generation rate and hydrogen evolution efficiency.