Effect Of Graphdiyne Cocatalyst On Photocatalytic CO₂ Reduction Performance Of Semiconductor

The energy crisis and environmental pollution are the most serious and urgent problems in the world.For alleviating the energy crisis and promoting the global carbon cycle,photocatalytic conversion of CO2 into solar fuels is unquestionably a charming strategy to "kill two birds with one stone".At present,a large number of semiconductors have been proven to be useful as photocatalysts for CO2 reduction.However,the performance of traditional semiconductor photocatalysts are usually low due to the high recombination rate between photogenerated electron and hole,insufficient surface active sites,limited CO2 adsorption ability and poor light absorption.These shortcomings severely limit the photocatalytic activity of these semiconductor photocatalysts.Graphdiyne(GDY)is a new type of 2D carbon material formed by sp-and sp2-hybridized carbon.This carbon material has large specific surface area,abundant surface active sites and high electron mobility.Moreover,its unique electron-deficient structure is more conducive to the electron transfer and capture,which can promote the separation of photogenerated carriers and increase their lifetime.In this parper,the effect of graphdiyne cocatalyst on photocatalytic performance of semiconductors was studied.The main contents of this paper are as follows:1.Synthesis of CdS/GDY composite for photocatalytic CO2 reduction.CdS nanoparticles were synthesized by a one-step hydrothermal method.Graphdiyne was added during this process,which enabled CdS nanoparticles to in-situ grow on the surface of GDY nanosheets.The traditional CdS/graphene composite was prepared in the same system for comparison.Compared with the pure CdS nanoparticles and CdS/graphene composite,the photocatalytic performance of the CdS/GDY samples,containing 0.5 wt.%GDY,is greatly improved,and the total conversion rate of CO2 can reach 18.72 ?mol·g-1·h-1,which is 13.10 times that of pure CdS nanoparticles and 1.25 times that of CdS/graphene sample.Time resolved photoluminescence spectroscopy,X-ray photoelectron spectroscopy,electron paramagnetic resonance,photoelectrochemical test and theoretical calculations prove that there is a strong interfacial coupling between CdS and GDY,which not only provides a more convenient way for electron transport and improves the efficiency of electron transport,but also brings a large number of sulfur vacancies on the surface of the photocatalyst.These sulfur vacancies can capture photogenerated electrons and promot the separation of photongenerated carriers,which significantly enhances the photocatalytic CO2 reduction performance of CdS.2.Synthesis of Bi2WO6/GDY composite for photocatalytic CO2 reduction.The Bi2WO6/GDY composite was prepared by a one-step hydrothermal method and the GDY was added during hydrothermal process of Bi2WO6 nanosheets.Compared with pure Bi2WO6 nanosheets,the CO2 reduction perfomance of Bi2WO6/GDY sample was significantly improved.The total conversion rate of CO2 over the optimal Bi2WO6/GDY composite(with 3.0 wt.%GDY)can reach 2.36 ?mol h-1 g-1,which is about 5 times that of pure Bi2WO6.The results of experiment show that GDY can effectively separate photogenerated electron-hole pairs,provide rich active sites,promote carbon dioxide transport and adsorption.This work proves that GDY can be used as a high-efficiency cocatalyst for photocatalytic CO2 reduction,and provides new insight for exploring the applications of graphdiyne-like carbon materials in the field of energy conversion.