Plasma-assisted Synthesis Of Photocatalyst For Hydrogen Evolution From Water

As a kind of green energy,hydrogen was vital for solving the energy crisis and environmental pollution.Photocatalytic water splitting driven by solar energy is an efficient and environmental friendly hydrogen-produced method.However,the photocatalytic water splitting toward hydrogen evolution faced three major problems,such as limited light absorption capacity,severe photogenerated carrier recombination and sluggish surface reaction.Non-thermal plasma technology has been widely used in the fields of catalytst preparation and catalytic reactions due to the presence of a variety of high-energy active species.Based on these considerations,from the perspective of improving the efficiency of photocatalytic water splitting toward hydrogen evolution,a series of photocatalysts were synthesized using non-thermal plasma-assistted methods.The influence of non-thermal plasma in the structure of photocatalysts and the structure-activity relationship were systematically studied.It provided a new path for preparation of high-efficiency photocatalysts.The main results were listed as following:?1?From the viewpoint of that the defects can efficiently regulate the light absorption capacity of semiconductor photocatalysts,a preparation method for photocatalyst,which coupled non-thermal plasma and thermal polymerization,was developed.A series of N defect-rich C₃N_4-x photocatalysts were prepared,where N defects were in-situ constructed during the synthesis process for graphitic carbon nitride.Also,the effect of N defects on the photocatalytic activity of the C₃N_4-x was systematically investigated.The results showed that the C₃N_4-x loaded by Pt with the optimal photocatalytic hydrogen evolution activity reached 2461.8?mol?h^-1?g^-1,which was about 4.5 times higher than the activity of C₃N₄ prepared by traditional thermal polymerization.The remarkably improving of photocatalytic activity was caused by the enhancement of light absorption capacity and separation of photogenerated carriers.?2?From the viewpoint of that the Schottky junction can promote the separation efficiency of photogenerated carriers,A series of S defect-rich Cd/CdS_1-x Schottky junctions were prepared by surface treatment of CdS using non-thermal plasma,where can partly Cd²⁺species was reduced to metallic Cd in-situ.The structural changement process of the CdS in non-thermal plasma was systematically studied,and the influence of non-thermal plasma treatment time in the photocatalytic hydrogen evolution activity was investigated.The results showed that the Cd/CdS_1-x-x loaded by Pt with the optimal photocatalytic hydrogen evolution activity reached16.27 mmol?h^-1?g^-1,which was about 5.8 times higher than the activity of prestine CdS.The AQY was as high as 23.7%at the wavelength of 420 nm.The remarkably improving of photocatalytic activity was caused by the formation of Cd/CdS_1-x-x Schottky junction,which efficiently restrained the recombination of photogenerated carriers.?3?From the viewpoint of that the defects can efficiently regulate the hydrogen evolution reaction rates for cocatalysts,a series of S defect-rich MoS_2-x-x cocatalysts were prepared by non-thermal plasma.Then the prepared MoS₂ was used as cocatalyst of CdS for the photocatalytic hydrogen evolution.The influence of non-thermal plasma in the structure of MoS_2-x was systematically studied,and the effect of S defects on the photocatalytic hydrogen evolution activity for MoS_2-x-x cocatalysts was investigated.The results showed that the MoS_2-x obtained by the non-thermal plasma treatment exhibited the enhancement electrocatalytic HER activity.The photocatalytic hydrogen evolution activity of MoS_2-x/CdS was enhanced and the optimal activity reached 6.11 mmol?h^-1?g^-1,which was about 3.6 times higher than MoS₂/CdS.The S defects led to the significant increase in the surface hydrogen evolution reaction rate of the MoS_2-x cocatalyst,which effectively improved the photocatalytic hydrogen evolution efficiency of MoS_2-x/CdS.