Study On The Preparation Of Sulfur-Based Nanocomposites And Their Photocatalytic/ Electrocatalytic Performance

At the moment of environmental crisis and energy depletion,hydrogen as a new type of zero-pollution energy gas is a hot topic in recent years.In recent years,photocatalytic technology and electrocatalytic technology have shown great potential in photocatalytic water splitting.However,the search for efficient and cost-effective photocatalysts has aroused great interest in the scientific community.Similarly,the discovery of highly efficient non-precious electrocatalyst for the hydrogen evolution reaction（HER）in alkaline media is extremely attractive but also challenging in the field of renewable energy.In this study,metal sulfide catalysts with excellent catalytic performance and good stability were selected as research objects.The catalyst performance was further improved by metal and non-metal doping and co-catalyst.Therefore,this study synthesizes a cost-effective and environmentally friendly photocatalyst/electrocatalyst,which is of great significance in the field of clean energy.In this study,simple and safe solvothermal method was adopted,and N-ZnS,ZnS/Ti₃C₂,Pt/GO-ZnS and Ti₃C₂T_x/Ni₃S₂/NF with high catalytic activity were prepared by adjusting the doping amount and loading amount.the appearance of the synthesized sample by a series of characterization methods such as X-ray diffractometry（XRD）,transmission electron microscopy（TEM）,field emission electron microscopy（FESEM）,X-ray photoelectron spectroscopy（XPS）.Morphology,structural characteristics and functional groups etc.were analyzed;the catalytic performance of the prepared catalyst was evaluated by photocatalytic decomposition of water under the condition of lactic acid as a sacrificial agent or electrocatalytic decomposition of aqueous hydrogen by a three-electrode system.This study provides new ideas and useful insights for the development of sulfur-based catalysts and applications for clean energy hydrogen production.The main research contents and conclusions are as follows:（1）Novel N-doped ZnS microspheres were successfully synthesized by a facile one-step method.The as-prepared N-doped ZnS catalysts exhibited outstanding photocatalytic activities toward the removal of organic pollutants under natural sunlight and H₂ generation by water splitting.As expected,the rationally designed N-doped ZnS catalysts displayed significantly enhanced photocatalytic H₂ production performances,particularly N-ZS3,with the highest H₂ evolution rate of 243.61μmol g^-1 h^-1.In addition,in the presence of N-ZS3,ca.99%metronidazole removal was achieved within 150 min under natural sunlight irradiation.Furthermore,the prepared catalysts exhibited high photocatalytic performance towards the removal of various other organic pollutants,including methyl orange,methylene blue,rhodamine B,ciprofloxacin,and sulfanilamide.The high photocatalytic performances of the prepared catalysts were attributed to N doping,which increased the visible light absorption capacity and electron transfer efficiency of ZnS.Finally,reaction mechanisms for photocatalytic oxidation and H₂ generation were proposed.（2）Herein we have designed an innovative,non-heavy-metal-based hybrid photocatalyst via in-situ decoration of ZnS nanoparticles with Ti₃C₂ MXene nanosheets toward enhanced photocatalytic H₂production.The incorporation of Ti₃C₂ essentially promotes the charge transfer and extends the lifetime of photo-induced carriers,thereby resulting in an augmented H₂ production yield of 502.6μmol g^-1 h^-1 under optimal conditions,being almost 4-fold higher than pure ZnS(124.6μmol g^-1 h^-1).（3）Here,we have reported a photocatalytic-photodeposition step-wise strategy to prepare Pt/GO-ZnS photocatalysts and the inherent mechanism of the improved photocatalytic activities were systematically investigated.When evaluated for their photocatalytic properties,the as-prepared PZG-2（with the ratio of Pt and GO are 1 and 2 wt.%,respectively）exhibits excellent hydrogen production,and a H₂ evolution speed of up to 1082μmol g^-1 h^-1 under solar light irradiation,which was 8 times higher than that of pure ZnS.Similarly,as-prepared sample has great cycle stability.Furthermore,the photocatalytic mechanism was accordingly explored in the end.Photo-generated electrons in the conduction band（CB）of ZnS can be trapped immediately to GO and rapidly transfer to the Pt nanoparticles,as a result of the intimate-contact interface.（4）We present an experimental and theoretical exploration to demonstrate the in situ formation of binary MXene/Ni₃S₂ nanosheets over three-dimensional Ni foam（NF）,in target functioning as a self-supported and highly effective electrocatalyst for alkaline HER.Benefiting from the outstanding electrical conductivity,superior hydrophilic interface for gas release,and synergistic coupling of Ti₃C₂T_x and Ni₃S₂,the HER test on Ti₃C₂T_x/Ni₃S₂/NF in 1 M KOH results in a low overpotential（72 m V）to produce a current density of 10 m A cm^-2.The Tafel slope in response is 45 m V dec^-1,which is among the lowest realized for self-supported Ni-based electrocatalysts as well as the state-of-the-art MXene-involved electrocatalysts in alkaline media.Thus-designed catalyst is highly stable for at least 12 h,with no decrease in the current density.