Design And Synthesis Of Transition Metal (Ni-Cu) Electrocatalyst For Overall Water Splitting

As a kind of sustainable clean energy,hydrogen can replace the traditional fossil fuel as a new type of the fuel and has received extensive attention.Developing and exploring a high efficiency non-precious metal-based electrocatalyst for for overall water splitting is highly desired.Herein,the study proposes a simple and practical method to synthesize copper-introduced three-dimensional(3D)nanocluster nickel coatings(Ni-Cu)via a one-step self-etching electrodeposition.During the process of electrodeposition,the copper substrate was corroded to form ammonium copper ions,and by controlling the current density and the combined effect of sodium chloride in the electrolyte,a Ni-Cu electrocatalyst was successfully prepared.Among the samples,CN-7 has the best electrocatalytic performance.The overpotential of hydrogen evolution reaction(HER)and oxygen evolution reaction(OER)is 76 m V and 290 m V at current density of 10 m A/cm~2,respectively.The long-time stability in 1 M KOH alkaline media can be reached.In addition,the first-principles calculation demonstrates that the electrocatalytic performance is better than those of pure copper or nickel coating,and the Gibbs free energy of the Ni-Cu alloy is reduced,resulting in the superior intrinsic electrocatalytic activity.The successful preparation of Ni-Cu electrocatalysts provides a new way for the electrodeposition synthesis of electrocatalyst.An outstanding HER electrocatalyst requires its Gibbs free energy△G_H*to be approximately zero,to balance the reaction barriers of adsorption and desorption steps.Herein,we screened a series of metal/non-metal elements dual-alloyed Ni-based electrocatalysis via virtue of density function theory(DFT)computations.As for binary alloy electrocatalysts,Ni-Cu3 model exhibits the highest catalytic activity for HER with△G_H*of-0.064 e V.In addition,nonmetallic element doping can remarkably optimize the hydrogen binding energy by modifing the electronic configuration of catalysts,thereby achieving an intrinsically enhanced HER activity.Herein,based on our theoretical predictions,we design and synthesize a novel Ni-Cu-C alloy catalyst with good chemical stability and high catalytic activity(only 87 m V at current density of 10 m A/cm~2)in alkaline media.Such excellent HER activity stems from the moderate hydrogen adsorption free energy△G_H*,copious amount of exposed active sites,and better electron-transfer ability.The computational predictions can successfully guide the experimental preparation of the highly efficient Ni-based HER catalysts.