Plasma Synthesis Of CoSe₂ Ultrathin Porous Nanosheets For Electrocatalytic Oxygen Evolution

Energy crises and environmental pollution have seriously threatened the survival and development of human beings.Therefore,developing new sustainable and efficient clean energy to replace traditional fossil energy is becoming more and more urgent.At present,hydrogen is one of the most ideal green energy,which can be produced from water electrolysis.However,OER is the anodic half-reaction of water electrolysis,which limits the overall rate of the water splitting greatly due to its slow kinetics.Therefore,it is of great significance to develop an efficient and stable electrocatalyst for oxygen evolution reaction.To date,due to the high catalytic activity,commercial catalysts such as Ru O₂,Ir O₂and other noble metal oxides are still the main candidates during the OER process of water electrolysis.However,due to the limited resources,high price,and the poor stability,noble metal catalysts are far from being the best choice for oxygen evolution catalysts.The transition metal diselenide MSe₂(M:Fe,Co,Ni)are not only rich in resources,but also relatively inexpensive.Besides,they have special structural and electronic properties.In recent years,they have gradually attracted the attention of researchers.However,the performance of transition metal diselenide is not good enough currently.In this thesis,aiming at the preparation of more efficient and stable OER catalysts,plasma dry exfoliation treatment of inorganic-organic hybrid sheets is developed to synthesize selenium-vacancies rich Co Se₂ ultrathin porous nanosheet for electrocatalytic oxygen evolution.The main contents are as follows:(1)We prepared the CoSe₂ ultrathin porous nanosheets with Se vacancies successfully.And then the morphology,structure and composition of the products were characterized comprehensively and systematically.Firstly,we synthesized the Co Se₂/DETA inorganic-organic hybrid precursor through the simple solvothermal method;then,the DETA organic layer between the Co Se₂ inorganic layers in the precursor was removed by the cleaning action of Ar plasma.In addition,the etching and reduction of Ar plasma lead to the formation of porous structure and selenium vacancies,respectively.The as prepared cubic rich Se-vacancies ultrathin porous Co Se₂nanosheet with an average thickness of?1.5 nm can be successfully synthesized.(2)OER tests exhibited that the Se-vacancies rich Co Se₂ ultrathin porous nanosheets(Co Se₂ UNM_vac)have excellent OER catalytic properties.Its overpotential is only?284 m V at a current density of 10 m A cm^-2,and the stability can be retain for over 20 h.The mass activity was 789.1 A g^-1 at an overpotential of 300 m V,which was nearly 4 times and 120 times higher than those of Co Se₂ NS and Co Se₂ NP,respectively.In addition,the LSV curve of Co Se₂ UNM_vac still showed good performance after normalization by electrochemically active surface area,indicating that the active site in Co Se₂ UNM_vac has higher intrinsic activity.The research provides new ideas of designing efficient and stable oxygen evolution catalyst.