In-Situ Synthesis Of Ni-Co Foam Supported Multiphase Catalyst And Performance Study On Hydrogen Evolution Reaction By Electrochemical Water Splitting

All the time,The development and utilization of traditional fossil energy has always been the main force driving social progress and economic growth.At present,in the face of profound changes unseen in the world in a century,the transformation and upgradation of old and new kinetic energy have brought development opportunities for world economic growth.Exploring new energy sources and developing new driving forces can alleviate the excessive demand for fossil energy and promote the construction of green ecological environment.Hydrogen energy is a kind of green energy with high combustion calorific value,clean and pollution-free,and there are a variety of production methods,among which electrochemical water splitting for hydrogen production has become one of widely studied hydrogen production measure at present,due to its advantages of simple process,cheap equipment and high hydrogen purity.Electrode material is an important carrier to promote electrochemical water splitting,but the process of hydrogen-producing industrialization is restricted by slow kinetics,high overpotential,low active site,poor stability and other factors of most catalysts.Therefore,the design and development of cathode electrocatalysts with excellent electronic structure,abundant active sites,low overpotential and high activity is the key to breakthrough the efficient hydrogen evolution reaction.At present,self-supported catalysts have become the first candaidate for hydrogen evolution electrocatalysts because of their low resistance,good stability and easy operation and other characteristics.However,the research on using bimetallic nickel-cobalt foam（NCF）as the substrate is few.The Niand Cofrom the substrate can not only promote the adsorption/desorption balance of H*,but also save the additional introduced raw materials and maintain higher electrical conductivity.In view of this,in this paper,using the NCF as a hard conductive substrate,and multiphase composite material was constructed on the surface of NCF by hydrothermal,surface modification,annealing and other processes,which synergistically improve the intrinsic activity of the catalyst and promote the efficiency of electrocatalytic hydrogen evolution（HER）.The details are as follows:（1）Cu/NCF precursor was synthesized in situ on NCF by hydrothermal method,and then Cu₃P/NiCoP/NCF complex material was successfully prepared by low temperature phosphating,which was used for hydrogen evolution reaction under different pH conditions.Cu₃P and NiCoP showed a good synergistic effect,and the main active catalytic species NiCoP had an ideal hydrogen adsorption Gibbs free energy(ΔG_H*),which synergically improved the natural activity of Cu₃P and enhanced the hydrogen evolution performance.The unique curved trapezoidal nanosheet structure provided a larger active surface area,forming a rich gas release channel.The Ni-Cosubstrate enabled the catalyst to generate lower charge transfer resistance at the electrolyte interface,which promoted rapid electron transport.Therefore,when the current density is 10 m A cm^-2,the overpotential of Cu₃P/NiCoP/NCF in 1 M KOH,0.5 M H₂SO₄ and 1 M PBS electrolytes is as low as51 m V,87 m V and 151 m V,respectively.In addition,Cu₃P/NiCoP/NCF could also provide a high current density of at least 300 m A cm^-2.The chronopotentiometry test showed that Cu₃P/NiCoP/NCF can run stably for up to 24 h.After HER,subsequent XRD and XPS analysis further confirmed Cu₃P/NiCoP/NCF had ultra-stable structure and excellent durability in long-term operation.（2）The Cu/NCF precursor was nitrized to prepare a nitrogen-doped carbon coated multi-component NC@NiCoCu-N/NCF composite material.By adjusting the content and temperature to explore the law of change of catalyst morphology.The morphology observation showed that the trapezoidal nanosheets were transformed into disordered coral-like nanorods during the nitriding process.The rough nanorods s surface was conducive to better penetration of the electrolyte and providing more accessible active sites.In addition,nitrogen doped carbon could further enhance the conductivity of the catalyst,but also ensured that the internal active structure from the erosion of the electrolyte damage,improving the structural stability.There is a good synergistic interaction between Cu₃N Ni₄N Co₂N three phases,which makes the decomposition of H₂O and H₂release more balanced during the reaction,thus showing excellent hydrogen evolution performance.Therefore,when the current density reaches 10 m A cm^-2 in 1.0 M KOH and 0.5 M H₂SO₄,the overpotential of NC@NiCoCu-N/NCF composite is 89 m V and 131 m V and the corresponding Tafel slopes are 96 m V dec^-1 and 106 m V dec^-1,respectively.Chronopotentiometry showed that the catalyst could continuous operate at least 48 h in alkaline and acidic electrolytes,XRD comparison and SEM before and after the test indicated that the catalyst maintained excellent structural stability.（3）NiCoO_xS_y/NCF octahedron was prepared in situ by chemical oxidation and calcination vulcanization,and then a large number of dense NiWO₄ nanoparticles were constructed on the surface of NiCoO_xS_y/NCF octahedron by hydrothermal and annealing treatment,forming a typical core-shell structure.NiCoO_xS_y octahedron with rough surface enhanced the adhesion of NiWO₄ nanoparticles,showing a larger electrochemically active surface area and improving electron transport capacity.At the same time,the excellent electronic structure and interfacial synergies between the two phases enabled NiWO₄@NiCoO_xS_y/NCF to optimize the adsorption and desorption of hydrogen intermediates,promoting the efficient hydrogen evolution reaction.In 1 M KOH,NiWO₄@NiCoO_xS_y/NCF can provide an overpotential of 85m V at the current density of 10 m A cm^-2.In addition,the regular NiCoO_xS_yoctahedron requires an overpotential of 132 m V to reach a current density of 10 m A cm^-2 in 0.5 M H₂SO₄.Due to the advantages of in situ construction and core-shell structure,the catalysts ensured smaller impedance.NiCoO_xS_y/NCF and NiWO₄@NiCoO_xS_y/NCF aslo showed catalytic durability with continuous operation of 72 h.XRD and SEM analysis after testing also confirmed the stable structure of the catalysts.