Application Of Nickel-modified Tungsten Carbide Non-precious Metal Electrocatalyst On Hydrogen Electrode

At present,the increasing global demand for energy has led to the over-exploitation and use of traditional fossil fuels,causing serious energy crises and climate change.In order to follow the policy of sustainable development,people need to search and develop more new renewable energy to cope with huge energy demand.The development of clean new renewable energy can meet the growing energy needs of the world and maintain human sustainable development.Hydrogen has become a potential new generation of commercially available clean energy due to its high energy density and environmentally friendly reaction products.Electrocatalytic water splitting to produce hydrogen is a clean,environmentally friendly and efficient large-scale hydrogen production technology.The use of fuel cells can achieve efficient energy conversion between hydrogen energy and electrical energy.Hydrogen evolution reaction（HER）and hydrogen oxidation reaction（HOR）are important semi-reactions of electrochemical water splitting hydrogen production process and fuel cell,respectively,which greatly determines the efficiency of energy conversion.For the above reactions,precious metal catalysts such as Pt,Ru,and Pd have the best catalytic activity,but they are difficult to be applied on a large scale due to their expensive price,scarce resource abundance,and poor stability.Therefore,there is an urgent need to develop non-precious metal catalysts with excellent performance,low cost,and good stability to replace precious metal catalysts.Transition metal carbides are widely used in many fields of electrocatalysis.Due to the similar electronic structure to platinum,the application of transition metal carbides as non-precious metal catalysts for electrochemical energy conversion devices has important potential.Nickel is a common elemental component in catalyst materials.Many research reports have confirmed that whether nickel is doped or modified or formed into compounds,it plays an important role in improving catalyst activity.Based on this,this study reported that Ni-doped tungsten carbide nanocubes supported on foam metal（nickel foam）were ustilized as HER non-noble metal catalysts under full p H.At the same time,Ni_xW_yC-type binary metal carbide-supported on the nickel foams with various configurations were also designed and synthesized,and studied as HOR non-noble metal catalysts under alkaline conditions.The main research content of this disertation is divided into two parts:1.Using foamed nickel as a base material,nickel-doped modified tungsten carbide nano cubes(W_1-xNi_xC NCs/NF)have been prepared in-situ by hydrothermal-annealing method.Nickel foam as a base,in addition to supporting role,also was used as a nickel source to dope tungsten carbide for improving its catalyst activity.The W_1-xNi_xC NCs/NF catalysts was found to exhibit a hydrogen evolution overpotential of less than 50 m V in the entire p H range,and maintained over 50 h at a current density of 50 m A/cm² in the entire p H range.As a HER catalyst,its peak potential reaches a level close to that of commercial Pt/C catalysts,and it exhibits good stability in all p H environments.2.Applying hydrothermal method,two different configurations of Ni_xW_yC binary metal carbides are synthesized on the foam nickel substrate by adjusting the content of nickel source.As a comparison,binary carbide-loaded reduced graphene oxide（r GO）was also designed and synthesized.This study clarified the structure-activity relationship between the catalyst material structure and the HOR catalytic performance.In the alkaline oxidation test,the Ni₆W₆C NPs/NF and Ni₂W₄C NPs/NF catalysts exhibited a current density of 2.3 m A/cm² at a potential of 100 m V and a current density of 1.3 m A/cm² at a potential of 100 m V,and Ni₆W₆C NPs/NF catalyst showed almost no attenuation after 20,000 s stability test and showed excellent stability.As a HOR catalyst under alkaline conditions,Ni_xW_yC/NF exhibits an overpotential close to that of precious metal catalysts,and has advantages in limiting current density.