Construction Of 3D Transition Metal Sulfide Z-type Heterojunction And Study On Photoelectrocatalytic Performance

With the unscientific use of non-renewable energy sources such as fossil fuels and the rapid development of industrial and agricultural production,the global energy crisis and environmental degradation have become increasingly serious,which is also the main challenge facing humanity today.Therefore,we urgently need to find a green method to produce alternative clean and non-polluting renewable resources and degrade many pollutants in water to Solve energy and environmental issues.Hydrogen peroxide（H₂O₂）,as a carbon-free energy carrier,is a very important green chemical.It is widely used in bleaching reagents,chemical synthesis reactants,rocket propellants,antibacterial agents and water purification agents.In recent years,photoelectrocatalytic（PEC）technology as a new method has triggered extensive research from scholars which not only use for the catalytic production of various energy sources,but also for the degradation of pollutants to alleviate environmental pressure.Therefore,two sets of Z-type dual-function 3D sulfide semiconductor heterojunction catalysts were designed and prepared as photoelectrode materials,including graded flower-like MoS₂@CoMoS₄ heterojunction and cubicα-MnS@CuS heterojunction for H₂O₂ production and degradation of pollutants.The main research contents of this article are as follows:（1）Designed and constructed 3D hierarchical MoS₂@CoMoS₄ Z-type semiconductor heterojunction.In the 3D CoMoS₄ microflowers stacked by 2D nanosheets,the nanosheets cross each other to form a large amount of free space in the microstructure,and will significantly increase the specific surface area of CoMoS₄.In addition,each nanosheet serves as a proppant both can provide a good contact interface to load other semiconductors to form heterojunction hybrids,which is beneficial to the vertical growth of MoS₂ nanosheets to form 3D graded flower-like morphology of MoS₂@CoMoS₄,with a larger surface area and better visible light absorb.At the same time,metal sulfides have excellent photoelectric properties,the narrow band gap and the presence of sulfur,they facilitate the adsorption of molecular oxygen,thereby accelerating the catalytic reaction process.Through free radical trapping experiments,combined with Mott-Schottky results,it was proved that a Z-type p-n heterojunction was formed between MoS₂ and CoMoS₄,and the PEC mechanism was discussed in detail.The formation of the Z-type p-n heterojunction not only significantly promotes the light-induced separation efficiency of e^-and h⁺pairs,but also has a stronger redox capacity.Under the action of visible light irradiation/specific additional bias,the photocatalytic performance of MoS₂@CoMoS₄ was studied by producing hydrogen peroxide（H₂O₂）/p-aminophenol（p-AP）and degrading lomefloxacin（LOM）.Within120 minutes,the yield of H₂O₂ reached 205μM,the conversion rate of p-AP reached 72% within 180 minutes,and the LOM degradation efficiency reached 180%.After four cycles of testing,MoS₂@CoMoS₄ still has very good cycling stability.（2）Designed and constructed a graded massiveα-MnS@CuS semiconductor heterojunction.When the reaction solvent is pyridine,the prepared MnS isα-MnS,which has a relatively regular cubic shape.This regular cubic structure is conducive to the uniform and close vertical growth of 2D Cu S nanosheets on theα-MnS surface.A homogeneousα-MnS@CuS heterostructure is formed.At the same time,metal sulfides have excellent photoelectric properties and a relatively narrow band gap,and because of the presence of sulfur,they facilitate the adsorption of molecular oxygen,thereby accelerating the catalytic reaction process.Through free radical trapping experiments and Mott-Schottky results,it was proved that a Z-type p-p heterojunction was formed betweenα-MnS and CuS,and the PEC mechanism was discussed in detail.The formation of the Z-type p-p heteronode not only significantly promotes the light-induced separation efficiency of e^-and h⁺pairs,but also has a stronger redox capacity.Under the action of visible light irradiation/specific additional bias,the photocatalytic performance ofα-MnS@CuS was studied by producing H₂O₂ and reducing Cr（VI）.The yield of H₂O₂ reached 1.6mM within 180min,and the reduction rate of Cr（VI）reached 80%within 120min.In addition,after four cycles of testing,α-MnS@CuS still has very good cycle stability.