Preparation Of Chalcogenides-based Photocatalysts For Hydrogen Evolution Reaction

Energy is the cornerstone of human survival and the basis of the operation of society.Currently,energy shortage and environmental pollution require the development of clean and renewable energy.Solar energy,an inexhaustible green energy source,has enormous potential to substitute traditional fossil fuels.The conversion of solar-chemical energy and storage process are facilely implemented in large scale.Thus it is universally considered to be an ideal energy alteration path.Hydrogen has become the most promising energy format due to the high energy density and environmental friendliness.Therefore,it is an effective way to realize sustainable development via water splitting for hydrogen evolution accomplished by exploiting photocatalysts and solar energy.Up to now,abundant catcalysts have been synthesized and applied in hydrogen evolution.But the performances are far from expectation for the limited light-trapping capacity and transient lifetime.Metal chalcogenides with excellent light absorption,tailorable energy band structure and convenient modification are widespread employed in photocatalytic hydrogen evolution.Doping engineering is one of the effecitive approaches to regulate the electronic structure and promote the separation efficiency of photogenerated carriers.The introduction of nonmetal atoms like O and P is helpful to enlarge the interlamellar or lattice fringes,regulate the band structure and improve the optical properties of catalysts.Therefore,the separation of carriers is accelerated and the photocataytic activity is enhanced.In this paper,two photocatalytic systems with excellent performances are designed based on metal chalcogenides which are modified by doping engineering.The main contents are as follows:（1）Synthesis and photocatalytic hydrogen evolution performance of O-Mo S₂/Mn_0.5Cd_0.5S composites:the O dopants are introduced by one-step hydrothermal method and O-Mo S₂/Mn_0.5Cd_0.5S composites are fabricated by a facile ultrasonic method.The photocatalytic performance for hydrogen evolution is investigated under visible light illumination.When the O-Mo S₂ content is 12 wt%,the hydrogen evolution rate is the highest,reaching 84.32 mmol g^-1 h^-1,which is 3.18 times that of Mn_0.5Cd_0.5S(26.51 mmol g^-1 h^-1).Associated with characterization results of phase structure,morphology and photoelectrochemical properties,the intergration of O atom triggers abundant defects,activates the basal S atoms and increases active sites,therefore promoting the performance of hydrogen evolution.The improved photocatalytic property is attributed to the accelebrated electron transfer process and the declined recombination possibility of photoinduced carriers at the interface where O-Mo S₂ and Mn_0.5Cd_0.5S is tightly in contact.（2）Synthesis and photocatalytic hydrogen evolution performance of 1T/2H Mo Se₂/P-Cd S composites:the Cd S nanorods and 1T/2H Mo Se₂ nanosheets are prepared by hydrothermal process.The P dopants are introduced by low-temperature calcination treatment of Cd S with the addition of Na H₂PO₂ as the phosphorus source.The 1T/2H Mo Se₂/P-Cd S composites are synthesized by the ultrasonic methodology.Photocatalytic performance for hydrogen evolution is tested under visible light illumination.The result demonstrates that 8 wt%1T/2H Mo Se₂/P-Cd S diaplays the best performance,the rate of which is as high as 166.85 mmol g^-1 h^-1,38.6times that of P-Cd S(4.32 mmol g^-1 h^-1)and 60.2 times that of Cd S(2.77 mmol g^-1 h^-1).Combined with characterization results,the improved photocatalytic performance is assigned to the doping P element which prolongs the lifetime of photogenerated electrons and facilitates the transfer of carriers to the 1T/2H Mo Se₂ nanosheets...