Photocatalytic Hydrogen Evolution Coupling With Aromatic Alcohol Transformation

Recently,a dual-functional photocatalytic reaction system with coupled selective organic reductions and oxidations has been presented.In this coupled reaction system,both the photogenerated electrons and holes can be simultaneously utilized to generate value-added products,make the overall process more valuable from a sustainability and economic perspective.In this paper,cadmium sulfide(CdS)is used as the research object,and CdS is modified by co-catalyst loading and heterojunction construction,to develop photocatalytic materials with excellent performance,with particular emphasis on merging selective organic oxidation and reduction reactions and coupling selective organic transformations with chemical fuel generation(e.g.,H2).Although research in this area still in its infancy,it is expected that this dual-functional technology offers opportunities for the development of next-generation selective organic transformation processes that meet the economic,societal,and ecological expectations.Based on the above requirements,a photocatalytic system for selective transformation of organic compounds coupled with hydrogen production was developed.The main contents of this paper are as follows:(1)The composite catalyst has been successfully prepared.P25-Ni2P photocatalyst prepared through loading the cocatalyst Ni2P on the surface of commercial titanium dioxide(P25)by doping with the precursor,then the composite catalyst has been recombined with CdS obtained by solvothermal method to form heterojunction photocatalyst,which leaded to the CdS&P25-Ni2P photocatalyst that simultaneously achieved photocatalytic hydrogen production and selective transformation of aromatic alcohol under visible light condition.In this reaction system,the traditional sacrificial agent oxidation reaction is replaced by the dehydrogenation reaction of aromatic alcohol with higher additional value,where highly efficient photogenerated carrier utilization can be realized.In this system,the hydrogen produced is diffused into the gas phase,while the oxidation product of aromatic alcohol is left in the liquid phase,which can achieve the automatical separation of products and inhibit the occurrence of reverse reaction,thereby improving the overall efficiency of the reaction;(2)A variety of characterization methods have been used to characterize the structure and composition in detail.The reaction performance of CdS&P25-Ni2P photocatalytic hydrogen production coupled with the dehydrogenation of aromatic alcohol under visible light conditions has been investigated.The effects of solvent effect,substituents effect,photocatalyst loading ratio,co-catalyst loading location and other factors on this reaction were explored.The results show that the introduction of Ni2P can greatly improve the ability of CdS-P25 to catalyze the aromatic alcohol dehydrogenation transformation and photocatalytic hydrogen production activity.The photocatalytic hydrogen production efficiency is 2 times that of pure CdS,44 times higher than that of CdS&P25,and 100 times that of P25-Ni2P.Under the conditions of visible light irradiation and the optimal catalyst ratio,in the aqueous solution,the conversion rate of the substrate can reach about 70%within 2 h,and the maximum hydrogen production rate can reach 0.986 mmol gcat-1h-1.And in organic solution,the substrate is almost completely transformed within 5 h,and the hydrogen production rate can reach 1.148 mmol gcat-1·h-1;(3)Photoelectrochemical characterization demonstrated that Ni2P plays an important role in promoting the photocharge separation of CdS-P25 and enhancing the photocatalytic activity;(4)Through the research of different reaction systems,aldehydes and lactones have been obtained in water system and organic system.According to the experimental results,different possible reaction mechanisms for selective organic transformation coupling with hydrogen evolution under visible light irradiation have been proposed.Based on the basic understanding of the CdS-P25 photocatalytic materials,this paper further explores the feasibility viewpoint and scheme for future in-depth application in the field of organic value-added transformation coupled with hydrogen production through continuous exploration of its catalytic performance,and provides a new strategy for the effective use of photogenerated electrons and holes,which will be inspirational for the future involving catalysis,materials and other fields.