The Preparation And Properties Of Cu-in/cuins₂ Composite Thin Films

The rapid development of modern industry has accelerated the emission of CO2.The large changes of global temperature have seriously affected the normal production and life of people.Thus countries around the world have explored and studied technologies to reduce CO2 to clean fuels.Among the CO2 comprehensive utilization technologies,the photoelectrocatalytic reduction of CO2 is a technology with good development prospects.The new challenge of photoelectrochemical reduction of CO2 is to design highly selective,highly efficient and non-precious metal catalysts.For carrying out the photocatalytic reduction of CO2 to ethanol on the surface of CuInS2 film,in this paper,the CuInS2 film was surface-modified with Cu-In alloys,and the effects of different preparation methods of Cu-In alloy on the chemical composition and properties of Cu-In/CuInS2 composite films were investigated,the results are as follows:(1)When the Cu-In alloys were prepared by the two-step method,the CuZO particles were deposited in the first step.The preparation conditions of Cu2O were:the pH of the electrodeposition solution was 10,the deposition time was 5 s,and the deposition potential was-0.7 V(vs.SCE).The In particles were deposited in the second step,the preparation conditions as follows:the deposition potential was-1.25 V(vs.SCE),and the deposition time was 30 s.The Cu-In alloys were prepared by one-step method to modify the CuInS2 films.The optimal preparation conditions were as follows:triethanolamine was used as the complexing agent,the deposition potential was-1.25 V(vs.SCE),and the deposition time was 10 s.(2)XRD,EDS and XPS were used to determine the chemical composition of the composite.In the two-step method,impurities such as In2O3 were formed during the deposition of In particles,and adhered to the surface of Cu-In alloy and CuInS2 film,which reduced.the surface activity of the composite film;the Cu-In/CuInS2 composite film prepared under one-step conditions has less impurities in other metal compounds,which is beneficial to the reduction of CO2.(3)It was found in the UV-Vis test and photocurrent test that the Cu-In/CuInS2 composite film has high absorbance and photoreaction current,which can inhibit the recombination of photogenerated electrons and photogenerated holes,which is beneficial to electron transfer.Compared with the two preparation methods,the Cu-In/CuInS2 composite film prepared under the one-step condition has the best optical performance improvement;the AC impedance experimental analysis shows that the rate of CO2 reduction is determined by both the interface charge transfer resistance and mass transport limitation.(4)Combined with the analysis of the adsorption intermediates,it can be favorable that the relative content of Cu-In alloys in the composite film and the degree of Cu-In alloying are high,which can suppress HER and enhance the surface coverage of*CO,meanwhile,promote C-C coupling and further improve the conversion of CO2 to ethanol.