Preparation Of Black Phosphorus Quantum Dots/MoS₂ Heterojunction Electrocatalyst And Its Photo-Assisted Enhancement Performance

With the aggravation of energy crisis and environmental problems,electrocatalytic water splitting has a good development prospect.Due to the complex electrocatalytic reaction process,oxygen evolution reaction（OER）often requires high energy barriers,leading to the significant energy loss and reducing the overall efficiency of energy conversion.Therefore,we need to find an efficient electrocatalyst.Molybdenum disulfide（MoS₂）is a typical two-dimensional（2D）material with abundant reserves and unique electronic structure.However,its limited number of active sites severely hinders its application in electrocatalytic OER.Black phosphorus quantum dots（BP QDs）with large exposed surface area and a large number of active edge sites are easily supported on MoS₂ nanosheets to form Type-II heterojunctions,bringing more active sites and higher mobility,effectively improving the OER performance of MoS₂.In addition,we find other ways to reduce the energy loss and improve the OER performance of the material.Combining photochemical and electrochemical energy conversion is an effective way to improve energy conversion efficiency.Photo-assisted and NADPH are utilized to reduce the high energy barrier and energy loss of OER,thereby improving the overall efficiency of energy conversion.The main research contents are as follows:1.The BP QDs and MoS₂ nanosheets were prepared by the liquid phase exfoliation method,and mixed-dimensional BP QDs/MoS₂ heterojunction were constructed.The morphology and microstructure were systematically characterized.The electrocatalytic oxygen evolution performance was tested by the electrochemical workstation.The experimental results show that the OER performance of the BP QDs/MoS₂ heterojunctions is better than that of pure MoS₂ nanosheets and BP QDs,with lower Tafel slope,onset potentials,charge transfer resistance R_ct and overpotential at 10m A/cm².The value of capacitance of electrochemical double layer is approximately 20.9 times that of pure MoS2,which means the heterojunction has a larger active surface area.In addition,changing the concentration of KOH electrolyte can also be used as one of the methods to tune the OER performance.Meanwhile,both composites and MoS₂ showed strong stability in KOH solution.This part of the research shows that constructing BP QDs/MoS₂ heterojunctions is an effective strategy to promote electrocatalytic OER performance.2.The electrocatalytic OER performance of mixed-dimensional BP QDs/MoS₂ heterojunctions was tested by the electrochemical workstation,with and without light-assisted conditions.The results show that the OER performance of the heterojunction under light-assisted condition is better than that under dark condition,the measured onset potential,overpotential at 10 m A/cm²,Tafel slope and R_ctare all lower.In addition,the electrocatalytic OER performance of the heterojunction with or without NADPH addition in the electrolyte was further tested under light-assisted conditions.The heterojunction with NADPH added to the electrolyte exhibited lower onset potential,overpotential at10 m A/cm²,Tafel slope and R_ct,and improved OER performance.Meanwhile,in both cases,changing the concentration of KOH electrolyte can also tune the OER performance,and the heterojunction has good stability in KOH solution.This part of the research shows that both photo-assisted and addition of NADPH to the electrolyte under photo-assisted conditions are effective methods to facilitate the electrocatalytic OER performance.