MOF-74-based Self-supporting Nanoarray Electrode Material Electrocatalytic For Water Splitting In Alkaline Conditions

With the development of the world economy,the increasing consumption of fossil fuels such as coal,natural gas and oil,and the increasingly prominent environmental problems,the demand for cheap,clean and sustainable energy is increasing day by day.Therefore,the development of environmentally-friendly new energy is imminent.Hydrogen has the advantages of large calorific value,no pollution,cleanness,high efficiency,etc.It is considered as an ideal alternative energy source for fossil fuels with broad development prospects.At present,photoelectric conversion and electrocatalytic water splitting is widely considered as one of the best ways to store energy from renewable energy sources-water to generate hydrogen resources.The electrolyzed water reaction includes the cathodic hydrogen evolution reaction（HER）and the anodic oxygen evolution reaction（OER）.Usually catalysts are required to reduce their activation energy.At present,the commercially used catalysts are basically precious metals and their oxides.However,their high cost,low abundance,and easy inactivation make their commercial applications extremely limited.In order to apply to large-scale production and promote the development of the hydrogen energy industry,seeking high-efficiency,low-cost HER and OER catalysts is the current industry research focus.Metal organic framework（MOF）is regarded as a kind of porous materials with wide functions in energy conversion system because of its unique three-dimensional pore structure,super-high specific surface area and good distribution of active metal sites.In this paper,W_xCo_1-x-MOF-74@NF（0≤x<1）material was first prepared by a simple one-step solvothermal method using nickel foam as a substrate,and then,the morphology and composition of the material were characterized by ways of XPS,SEM,XRD,EDS,and TEM.The influence of the structure of the catalyst material on its catalytic performance was also analyzed.Here,tungsten（W）is introduced into Co-MOF to adjust its electronic band structure.The original Co-MOF-74 nano-arrays with different W contents were synthesized on nickel foam and used as electrodes for high-efficiency electrocatalytic hydrogen evolution.Co-MOF-74@NF modified by W showed significant catalytic activity,especially the preferred sample W_0.5Co_0.5-MOF-74@NF required only-105 m V and-286 m V potentials at a current density of-10 m A cm^-2 and-0.35A cm^-2 in HER tests,respectively.In addition,in this paper,the potential was recorded at a constant current density of-10 m A cm^-2.The W_0.5Co_0.5-MOF-74@NF electrode showed almost no significant change after a long-term HER test,which indicates it has highly HER catalytic stability.The results show that Tungsten（W）plays an important role in optimizing the HER performance of the original Co-MOF-74 catalyst.Based on the fact that Fe is a common catalytic component,furtherly,W_xFe_1-x-MOF-74@NF（0≤x<1）was prepared by one-step solvothermal method using nickel foam as the substrate.Technologies including SEM,XRD,EDS,XPS et al.were used to characterize its morphology and structure,and study the effect of the structure of the catalyst material on its catalytic performance.W_xFe_1-x-MOF-74@NF（0≤x<1）catalytic materials showed significant oxygen evolution catalytic activity,especially for the preferred sample W_0.2Fe_0.8-MOF-74@NF,only232 m V potential was required at a current density of 10 m A cm^-2.The potential tracing was carried out at a current density of 10 m A cm^-2 and showed that W_0.2Fe_0.8-MOF-74@NF electrode had almost no significant change after a long OER test,which indicates that the W_0.2Fe_0.8-MOF-74@NF electrode material has high electrochemical OER activity and stability under alkaline conditions.Finally,Co,Ni-based metal organic framework oxygen evolution catalyst grown in-situ on nickel foam was studied.Technologies including SEM,XRD,EDS,XPS et al.were used to characterize its morphology and structure,and study the effect of the structure of the catalyst material on its catalytic performance.The results showed a variety of Co_xNi_y-MOF-74@NF complexes could be successfully prepared using a one-step solvothermal method.Among them,Co_0.8Ni_0.2-MOF-74@NF showed excellent OER activity and good stability,provided a low overpotential of 275 m V at 10m A cm^-2,and had little activity attenuation within 40h.In this paper,W_xCo_1-x-MOF-74@NF self-supporting HER electrocatalytic electrode,W_xFe_1-x-MOF-74@NF self-supporting OER catalytic electrode,and Co_xNi_y-MOF-74@NF self-supporting OER electrode with column array structure were successfully prepared by one-step solvothermal method,showing excellent electrocatalytic activity and electrochemical stability.This method is simple,easy to realize,and has a wide application prospect.