The Study On The Production Of Hydrogen Peroxide By Au/BiVO₄ Photocatalytic System

Hydrogen peroxide（H₂O₂）,an important and green chemical product with H₂O as the only by-product,plays a vital role in the fields of chemistry,environment,medicine and energy.Photocatalytic H₂O₂ production with semiconductor photocatalysts is a novel strategy for converting solar energy into chemical energy.Among the numerous photocatalytic materials for producing H₂O₂,Au/BiVO₄ is one of the most promising photocatalytic materials for the H₂O₂ synthesis due to the suitable band structure of BiVO₄ and a large number of catalytic active sites and good selectivity of Au particles on the BiVO₄ surface.In practice,however,Au/BiVO₄ photocatalyst still exhibits limited catalytic activity for photocatalytic H₂O₂ production.One of the main reasons is that the reaction is slow involved by photogenerated holes,which are also easily consumed by the synthesized H₂O₂.In order to solve the above problems,in this paper,crystal engineering of BiVO₄ and the coordination strategy by the interaction betweenα-hydroxyl carboxyl citrate and surface exposed Biatoms are adopted to effectively improve the reaction rate of photogenerated holes,thus improving the photocatalytic performance of H₂O₂ synthesis.On this basis,we further propose a strategy of lanthanide gadolinium（Gd）doping to replace the surface Biatoms to effectively inhibit the decomposition of H₂O₂ at the Biatomic sites on the hole-exposed facets of BiVO₄;At the same time,the charge transfer between the interface of Au and BiVO₄ is also improved by the Gd doping,which effectively enhances the H₂O₂ production further.The specific research contents are as follows:First,single-crystal BiVO₄photocatalysts are prepared by a hydrothermal method,and then noble metal Au nanoparticles are selectively deposited on the（010）facet of single-crystal BiVO₄ by a simple photodeposition method.Hydrogen peroxide are generated by Au/BiVO₄photocatalyst under the regulation of citric acid（CA）coordination.The experimental results of photocatalytic H₂O₂ production by Au/BiVO₄photocatalyst in 0.5 mmol L^-1 CA system show that formed H₂O₂ concentration is as high as 1.45 mmol L^-1 with a quantum efficiency of 4.51%,which is relatively high performance of bismuth-based catalysts for H₂O₂ production and is about 28 times higher for H₂O₂ production than in CH₃OH,Et OH and oxalic acid reaction system.The mechanism of CA coordination regulation of Au/BiVO₄ photocatalytic production of H₂O₂ is proposed:CA molecules can coordinate with the unsaturated Biexposed on the（110）facet of BiVO₄ to accelerate the transfer and consumption of photogenerated holes,thus facilitating the production of H₂O₂ through two-electron reduction of oxygen.At the same time,CA molecules are selectively oxidized to produce effective intermediateβ-ketoglutaric acid（OGA）.Second,in view of the oxidative decomposition of H₂O₂ and the interfacial interaction problem of Au/BiVO₄ in the photocatalytic production of H₂O₂ in CA system,the lanthanide Gd is incorporated into single crystal BiVO₄ by a hydrothermal method to regulate the interface charge transfer between Au nanoparticles and BiVO₄and inhibit H₂O₂ decomposition.The experimental results of Au/BiVO₄:Gd photocatalytic H₂O₂ production show that formed H₂O₂ concentration is as high as2071.43μmol L^-1（AQE=6.44%）within 2 h,which is 1.43 times higher for H₂O₂production than Au/BiVO₄ photocatalyst.Therefore,the mechanism of photocatalytic H₂O₂ production by Gd-doped Au/BiVO₄ is proposed:the element Gd is doped into the single crystal BiVO₄ and Bi³⁺is selectively replaced by Gd³⁺,thereby reducing the photogenerated hole oxidation of Bi³⁺to generate Bi⁵⁺and inhibiting the oxidative decomposition of H₂O₂.And Gd doping modulates the electronic structure of BiVO₄,reduces the Schottky barrier between Au particles and BiVO₄,accelerates the photo-generated electron transfer,and promotes the reduction of O₂ to generate more H₂O₂.