Selective Photodeposition Of Cu-based Cocatalysts And Cu₂O On The Surface Of Bismuth Vanadate

BiVO₄ semicondutor material has received wide attention in photocatalysis due to its stable structure,strong visible-light absorption,and nontoxicity.However,it shows rapid recombination of photogenerated carriers and weak reduction ability of photogenerated electrons owing to its special band structure,which results in its low photocatalytic performance and thus limits its application.Experimental results indicate that surface modification is one of most effective strategies to improve the photocatalytic performance of BiVO₄,and the main modification methods include calcination,hydrothermal and impregnation.Compared with the above approaches,photodeposition approach possesses unique advantages.For example,it is green and mild because only solar energy and room temperature are needed.Additionally,it can realize in situ and solid modification on the surface of photocatalysts because they are formed by utilizing the corresponding photogenerated electrons or holes on the surface.Therefore,the approach has received intensive attention so far,and the successful modification materials mainly focus on noble metals（Au,Pt,Ag,etc）and transition metal based materials with rare resource（Co₃O₄ etc）.However,the low-cost and highly efficient modification materials on the BiVO₄ surface are rarely reported.Based on it,this paper mainly focuses on Cu-based modification materials by selective photodeposition on the（010）facets of single crystal BiVO₄ to carry out related work:（1）constructing efficient Cu₂O/BiVO₄ p-n heterojunction photocatalyst through selective photodeposition;（2）one-step photodeposition synthesis of highly efficient core-shell Cu@Bi cocatalysts to modify BiVO₄ photocatalyst.Specific research results are as follows:First,p-type Cu₂O semiconductor material was selectively photodeposited on the surface of n-type BiVO₄ semiconductor photocatalyst by selecting organic alcohol solvents and copper sources.The experimetal results indicated that polarity of organic alcohol solvents and combination abilities of cations and anions in copper sources played important roles in the formation of p-type Cu₂O.Furthermore,the photodeposition amounts of Cu₂O can be controlled by irradiation times,ratio of alcohol to water,and the amounts of copper source.The photocatalytic results indicated that Cu₂O/BiVO₄ composite photocatalyst exhibited obviously higher photocatalytic activity than BiVO₄.The photocatalytic mechanism was explained as follows.A space charge zone can be formed by p-n heterojunction in Cu₂O/BiVO₄ photocatalyst,which facilitated efficient separation of photogenerated carriers of Cu₂O and BiVO₄ and thus improved the photocatalytic performance of BiVO₄.Second,the core-shell Cu@Bi cocatalyst was selectively modified on the（010）facet of BiVO₄ by one-step photodeposition method using Cu（NO₃）₂ and Bi（NO₃）₃ as source materials,as well as ethylene glycol as sacrificial agent.The photocatalytic results showed that the obtained Cu@Bi/BiVO₄ photocatalyst exhibited excellent photocatalytic performance.Its rate contant was 10.5,5.5 and 1.8 times than that of BiVO₄,Bi/BiVO₄ and Cu/BiVO₄,respectively.The enhanced performance was ascribed to the synergistic effect of crystal-facet engineering of BiVO₄ and selective modification of Cu@Bi electron cocatalyst.In detail,the single crystal structure of BiVO₄ results in the orientation transport of photogenerated carriers,while metallic Cu effectively transfers photogenerated electrons of BiVO₄ and then Bi as the active site accelerates the interfacial reduction reaction.