| The development of human society today is facing severe problems of energy shortage and environmental pollution.The photocatalytic water splitting to produce hydrogen using inexhaustible solar energy is one of the best means to solve the energy problem.The generated hydrogen energy has a high calorific value and the combustion product is water,which can fundamentally reduce environmental pollution.The single semiconductor has the defects of low photocatalytic efficiency and severe photocorrosion.How to design a highly efficient and stable photocatalyst in the process of hydrogen production from photocatalytic water splitting,improving the separation efficiency of photogenerated carriers is the key in this research field.Loading effective cocatalysts is an effective method to improve photocatalytic hydrogen production.In this paper,non-noble metal is taken as the research object.We studied different types of noble metals,and assembled a composite hydrogen production co-catalyst of noble metal/non-noble metal WC,and then integrated with CdS to conduct photocatalytic water splitting for hydrogen production.By studying the capacitance of WC and the effect of noble metal kinds on the composite co-catalysts,the optimal WC co-catalyst and(Pd/WC)composite co-catalyst were obtained.The specific research contents are as follows:(1)Studies of the performance and mechanism of photocatalytic hydrogen production on(Ru/WC)/CdS and Ru/(WC/CdS).Using impregnation reduction method to prepare(Ru/WC)composite co-catalyst,then co-precipitation with CdS for hydrothermal synthesis(Ru/WC)/CdS.The optimal hydrogen production of the catalyst reached 16.85 mmol/h/g.And the composite co-catalyst is better than the single co-catalyst The photocatalytic activity of Ru/(WC/CdS)prepared by different assembly methods is shown as the hydrogen production activity of WC/CdS(Ru%=0.001%),which is equivalent to the sum of a part of Ru/CdS and a part of WC/CdS(Ru%=0.01%or 0.1%),which is almost the same as the photocatalytic hydrogen production activity of Ru/CdS(Ru%=0.5%or 1.0%).The linear scanning voltammetry curve and electrochemical alternating current impedance spectroscopy proved that the introduction of Ru can effectively reduce the hydrogen production overpotential and interface charge transfer resistance of the co-catalyst,indicating that Ru in the composite cocatalyst plays a role in proton catalytic hydrogen production.The constant current charge-discharge curve proves that WC has a large specific capacitance,which mainly serves to store electrons.Photoelectrochemical experiments prove that the hydrogen production performance of the two photocatalysts is different due to different electron transfer paths:(Ru/WC)/CdS electrons are first transferred to WC and then to Ru,and electrons in Ru/(WC/CdS)are simultaneously transferred to Ru and WC,Ru and WC play a competitive role in transferring electrons.(2)Studies of the effect of capacitance on the catalytic performance of WC.Five kinds of WC are synthesized and compared with WC without added surfactant(WC-N)and commercial WC(WC-C).It was found that the WC-P synthesized by the introduction of the surfactant polyvinylpyrrolidone(PVP)showed a nano-flower shape.WC-P/CdS has the best hydrogen production activity,and the optimal hydrogen production can reaches 24.50 mmol/h/g,which is 1.75 times that of WC-C/CdS,1.60 times that of WC-N/CdS,and the apparent quantum efficiency is 10.77%at 523 nm.Compared with WC-N and WC-C,the overpotentials of the three co-catalysts are not significantly different The cyclic voltammetry curve proves that WC-P has the largest specific capacitance(12.07 F/g).The excellent cocatalyst performance of WC-P lies in its enhanced ability to store electrons.(3)Developed(Pd/WC-P)/CdS high-efficiency hydrogen-producing photocatalyst.The hydrogen production activity of photocatalysts composed of different noble metals and CUS was studied,and Pd was found to be the best noble metal.Assembling Pd with the optimal non-noble metal co-catalyst WC-P forms the optimal composite co-catalyst(Pd/WC-P),and then integrated with CdS to form(Pd/WC-P)/CdS.The photocatalytic hydrogen production is up to 29.5 mmol/h/g,and the stability of photocatalytic hydrogen production can reach 40 h.The apparent quantum efficiency can reach 14.13%at 523 nm.Compared with Pd/CdS and WC-P/CdS,(Pd/WC-P)/CdS has the highest surface photocurrent of 1700 ?A.This proves that(Pd/WC-P)composite co-catalyst is superior to single co-catalyst At this time,the photo-excited electrons in CdS are first transferred to WC-P,and then transferred to the surface of Pd to produce hydrogen.WC-P plays a role of storing electrons,and Pd plays a role of proton-catalyzing hydrogen production. |
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