Synthesis Of Iron-nickel Nanocomposites And Their Electrocatalytic Performance For Oxygen Evolution Reaction

With the rapid development of economics and technologies,the overuse of fossil-fuel-based energy sources has resulted in exhausted reserves and serious environmental pollution.Hydrogen,as one of the most ecofriendly and sustainable energy carriers,has been viewed as a promising alternative.Hydrogen production from electrocatalytic water splitting is considered to be an effective method for producing"green hydrogen",and electrocatalytic water splitting is composed of two half reactions of hydrogen evolution reaction(HER)and oxygen evolution reaction(OER).As one of the most challenging tasks is the OER on anode,which involves a sluggish multi-electron transfer process and limits their further development.At present,the precious metals Ru O₂ and Ir O₂ are efficient OER electrocatalysts,but they are costly,rare in reserve,and poor in stability,which limit their extensive commercial applications.Therefore,it is of great significance to develop efficient and cheap non-noble metal OER catalysts.Transition metal and carbon materials are rich on earth,low in cost,and their adjustable electronic state which can reduce the thermodynamic reaction barrier in the process of electrocatalytic water splitting.These are conducive to enhance the electrocatalytic efficiency,and benefit the research and design of catalysts in the electrocatalysis process.Based on this,we have carried out the following research:A novel non-precious Fe₂O₃ nanoparticles-decorated Ni O nanosheet(Fe₂O₃NPs@Ni O NSs)composite has been obtained by a rapid one-pot electrochemical exfoliation method,and can be used as an efficient oxygen evolution reaction(OER)catalyst.In the nanocomposite,the Fe₂O₃ NPs are uniformly anchored on the ultrathin Ni O nanosheets.At the same time,we also studied the influence of Fe/Ni molar ratio on morphology and catalytic activity.The Fe₂O₃ NPs@Ni O NSs nanocomposite possessed the high BET surface area(194.1 m² g^-1),which is very conducive to charge/mass transfer of electrolyte ions and O₂.Owing to the unique two-dimensional heterostructures and rational Fe content,the as-prepared Fe₂O₃ NPs@Ni O NSs show high catalytic performance,lower overpotential at 10 m A cm^-2(221 m V),smaller Tafel slope(53.4 m V dec^-1),and excellent durability.The introduction of Fe₂O₃ NPs is beneficial to accelerate charge transport,increase the electrochemically active surface area(ECSA),and thus improve the release of oxygen bubbles from the electrode surface.Iron-nickel alloys,phosphides and carbon materials have low cost,high catalytic activity and stability,which are ideal materials to replace precious metal catalysts.Therefore,we used iron and nickel nitrates,urea and citric acid as raw materials,through sol-gel method,heat treatment and phosphating treatment to successfully fabricate the composite(Fe Ni_x/Ni₂P-CNTs@PNCNSs)including Fe Ni_x/Ni₂P hybrid materials,carbon nanotubes(CNTs)and N-doped carbon nanosheets(PNCNS).This structural and componential engineering resulted in lightweight,continuous conductive network,unimpeded mass transfer and charge transfer channels,which is very helpful to improve the efficiency and stability of electrocatalysis.In 1 M KOH solution,the overpotential at 10 m A cm^-2 is 217 m V,and the Tafel slope is 37 m V dec^-1.At the same time,the as-prepared electrocatalyst showed good stability after continuous operation for 20 h.The excellent catalytic activity of Fe Ni_x/Ni₂P-CNTs@PNCNSs provides a promising synthesis strategy for integrating transition metal-based composite materials to assemble high-performance,low-cost fuel cells.