Enhancement Of Photocatalytic Hydrogen Production By Hydrogenase Model Complex Fe₂S₂（CO）₆ Coupled With MoS₂

With the rapid development of human society,how to solve the problem of sustainable reduction of non-renewable energy and ecological environmental pollution caused by the massive use of fossil fuels has become a research hotspot in the field of energy in the world today.The photocatalytic water splitting to produce hydrogen using abundant solar energy is one of the best technologies to solve the energy problem.In the photocatalytic decomposition of aquatic hydrogen,the performance of a single semiconductor is extremely low due to the low efficiency of photogenerated charge separation and transfer,serious photocorrosion and other shortcomings.How to design an efficient and stable photocatalyst and improve the efficiency of photogenerated carrier separation and transfer has become the key to extensive research by researchers.It is one of the effective methods to improve the separation and transfer efficiency of photocatalytic carriers and the performance of photocatalytic hydrogen production by loading suitable cocatalyst.In this paper,hydrogenase model complex Fe2S2(CO)6 and non-noble metal co-catalyst MoS2 were taken as the research object,Fe2S2(CO)6 and MoS2 were assembled to form complex co-catalyst.The mechanism of Fe2S2(CO)6 and Cys-MoS2 in photocatalytic decomposition of aquatic hydrogen and the enhancement of hydrogen production performance of bulk CdS were investigated.CdS QDs were used as photocatalysts.MoS2/CdS QDs were synthesized by wet impregnation with CdS QDs and MoS2,then Fe2S2(CO)6/MoS2/CdS QDs were self-assembled with Fe2S2(CO)6 to form Fe2S2(CO)6/MoS2/CdS QDs composite photocatalyst,and the performance and reaction mechanism of photocatalytic hydrogen production were investigated.The specific research contents are as follows:(1)Fe2S2(CO)6/Cys-MoS2 composite cocatalyst was designed,and to study the action mechanism of Fe2S2(CO)6 and Cys-MoS2 in photocatalytic decomposition of aquatic hydrogen.Fe2S2(CO)6/Cys-MoS2 composite cocatalyst was prepared by interfacial self-assembly,and then the(Fe2S2(CO)6/Cys-MoS2)/CdS was synthesized by wet impregnation with bulk CdS.The optimal hydrogen production performance reached 6660 μmol/g/h,which was 61.6 times that of CdS alone,9.7 times that of 5.0%Fe2S2(CO)6/CdS,1.4 times that of 1.0%Cys-MoS2/CdS.The infrared spectrum test shows that Fe2S2(CO)6 is assembled on Cys-MoS2 and provides transfer path for photogenerated electrons.The linear sweep voltammetry curve and electrochemical impedance spectroscopy demonstrated that the introduction of Fe2S2(CO)6 can effectively reduce the hydrogen production overpotential and interfacial charge transfer resistance,indicating that Fe2S2(CO)6 plays a role in proton catalysis of hydrogen production in the composite photocatalysts.The constant current charge-discharge curve shows that Cys-MoS2/CdS has a large capacitance,and Cys-MoS2 mainly plays the role of absorbing and storing electrons in the reaction process.Transient photocurrent response test shows that(Fe2S2(CO)6/Cys-MoS2)/CdS has the highest photocurrent,Fe2S2(CO)6/Cys-MoS2 load improves the separation and transmission efficiency of photogenerated carriers.(Fe2S2(CO)6/Cys-MoS2)/CdS showed better photocatalytic hydrogen production performance.(2)To study the photocatalytic hydrogen production performance and reaction mechanism of Fe2S2(CO)6/MoS2/CdS QDs.CdS QDs were synthesized and the composite catalyst MoS2/CdS QDs was synthesized by wet dipping with CdS QDs and MoS2,and then Fe2S2(CO)6/MoS2/CdS QDs was formed by self-assembly with Fe2S2(CO)6.The optimal hydrogen production activity of Fe2S2(CO)6/MoS2/CdS QDs reached 10836 μmol/g/h,which was 127.4 times that of single CdS,9.1 times that of Fe2S2(CO)6/CdS QDs,and 1.6 times that of MoS2/CdS QDs.TEM tests shows that MoS2 and CdS QDs have small size and are closely bound together,which is conducive to photogenic electron transfer.Capacitance test shows that MoS2/CdS QDs has a large capacitance and can store photogenerated electrons,which is conducive to the rapid separation of photogenerated carriers.The introduction of Fe2S2(CO)6 reduces the capacitance of MoS2/CdS QDs,indicating that Fe2S2(CO)6 promotes the further release of photogenerated electrons.Steady-state surface photovoltage test shows that Fe2S2(CO)6/MoS2/CdS QDs have weak photovoltage response,which indicates that the large capacitance of MoS2 and the strong electron releasing ability of Fe2S2(CO)6 result in the uniform distribution of photogenerated electrons on the surface.Transient photovoltage test showed that Fe2S2(CO)6/MoS2/CdS QDs had the strongest negative response,indicating that the introduction of Fe2S2(CO)6 caused the rapid transfer of photogenerated electrons to the surface,which was beneficial to the photocatalytic proton reduction hydrogen production.This is the main reason for the improvement of Fe2S2(CO)6/MoS2/CdS QDs photocatalytic hydrogen production performance.