Preparation And Properties Of MXene-Based Electrocatalysts For Hydrogen Evolution Reaction In Alkaline Media

Hydrogen energy is considered to be a powerful potential new energy source to solve today’s severe energy crisis and environmental problems.It not only has high energy density and zero pollution,but also can increase the utilization rate of wastewater.Hydrogen production from water electrolysis is a very critical part of the future hydrogen energy cycle system,and it is also one of the most economical and effective hydrogen production methods.It involves two half-reactions,the hydrogen evolution reaction（HER）at the cathode and the oxygen evolution reaction（OER）at the anode.The best hydrogen evolution catalysts so far are platinum group metals or their oxides,which are not only expensive but also have limited reserves.Therefore,it is necessary to find alternative catalysts with low cost,high catalytic performance and high stability.Due to the low H⁺concentration,the HER reaction in alkaline electrolytes is difficult to occur,so it usually has a high hydrogen evolution overpotential,so it is very important to develop catalysts that can efficiently stabilize hydrogen evolution in an alkaline environment.As a new member of the family of two-dimensional materials in recent years,MXene has shown great promise in energy conversion and storage due to its excellent electrical conductivity,large specific surface area,good hydrophilicity,and stable electrochemical properties.These excellent physicochemical properties of MXene are also very suitable for the construction of electrocatalytic hydrogen evolution materials,especially in alkaline media.Based on this,this paper has carried out the following research work:1.The traditional method of preparing MXene is inseparable from the participation of F element,and the-F dangling bond at the terminal of MXene is unfavorable for its HER catalytic performance.In this paper,a fluorine-free molten salt etching method is used.The precursor of MAX phase Ti₃Al C₂ was etched into Ti₃C₂T_x MXene material and Co atoms were successfully introduced into MXene.After further removing excess Co with sulfuric acid,Co-doped Ti₃C₂T_xMXene was obtained.The etching temperature and time were optimized,and the best etching conditions were obtained.Based on the experimental data and characterization results,the microscopic mechanism of the etching of Ti₃C₂T_x:Co samples is proposed.The electrocatalytic hydrogen evolution performance of the material was investigated by drop-coating Ti₃C₂T_x:Co on a glassy carbon electrode in 1 M KOH,and found that the sample treated with sulfuricacidfor 12 h had the best catalyticability,the overpotentialat thecurrentdensity of 10?m A cm^-2 is 103.6 m V and the Tafel slope is 104.32 m V dec^-1.2.Although noble metals have excellent catalytic properties,they usually have poor stability.We have developed a method for the preparation of ultrafine ruthenium nanoparticles using metal-organic framework compounds.First,a metal-organic framework ZIL-L（Co）with a regular morphology was grown by using few-layer Ti₃C₂T_x nanosheets as a template,and then by mild constant temperature ion exchange and low temperature annealing treatment,the ultrafine ruthenium nanoparticles supported samples Ru@ZIF-L（Co）/FL-Ti₃C₂T_x.The template effect of few-layer Ti₃C₂T_x nanosheets in the growth of ZIF-L（Co）was demonstrated by the experimental control without adding MXene and multilayer MXene.The experimental conditions for sample synthesis were optimized.The Ru@ZIF-L（Co）/FL-Ti₃C₂T_x catalyst prepared under optimal conditions achieves a current density of 10 m A cm^-2 in 1 M KOH solution with a hydrogen evolution overpotential of only 16.23 m V and a Tafel slope of 20.98 m V dec^-1,which is far superior to that of Pt/C catalysts in alkaline media.