| With the increase of fossil fuel consumption and the sharp decrease of reserves,hydrogen,Hydrogen as a new type of high energy density clean secondary energy is increasingly attracting attention.The methods of hydrogen production are different,among which electrolytic water is the first choice for large-scale hydrogen production because of its advantages of high purity and no pollution.To increase energy conversion efficiency,the key to solve the problem is to seek cathode materials with low hydrogen evolution potential and high stability.A large number of experimental results show that Pt group transition metals have the lowest hydrogen evolution overpotential,but their reserves are scarce and expensive,which makes them unsuitable for large-scale industrial production.Therefore,it is of great significance to develop cathode materials for electrolysis cells with low cost and high electrocatalytic-hydrogen evolution activity,which has become a focus of research in recent years.The purpose of this paper is to explore the method of dealloying to obtain special nanoporous structure electrode materials.At the same time,study on the addition of Mo and the difference of Mo content in the porous material,in order to obtain high activity and stability of the hydrogen evolution catalytic electrode.Nano-porous Ni,Ni-Mo alloys and their oxide electrode materials were prepared by rapid solidification and dealloying.The phase,morphology and pore size distribution of the electrode were characterized by XRD,SEM,TEM and BET.The electrocatalytic hydrogen evolution of porous electrode was tested by linear sweep voltammetry,Tafel slope AC impedance and chronopotentiometry.The results showed that the hydrogen evolution activity of Ni-Mo alloy was the highest at the current density of 10 m A·cm-2,and the hydrogen evolution process was controlled by Volmer-Heyrovsky step.The apparent exchange current density is 0.25×10-3 A·cm-2.After 10000 s constant current density(100 m A·cm-2),the hydrogen evolution overpotential increases only 39 m V.It shows excellent hydrogen evolution stability.The addition of Mo can improve the intrinsic catalytic activity of the electrode and further increase the specific surface area of the electrode.The overpotential of hydrogen evolution is reduced and the stability is good.The heat treatment results in the transformation of the amorphous structure to the crystalline state and the deterioration of the hydrogen evolution performance.The content of Mo has an important effect on the morphology,specific surface area and crystallinity of the nano-porous Ni-Mo alloy,and on the catalytic effect of the alloy on the hydrogen evolution reaction.Based on this,Ni-Mo alloy with different Mo content was prepared by dealloying method.The experimental analysis showed that Al and Al17Mo3 phases were found in the precursor Ni-Mo-Al alloy with high Mo content.The alloys with lower Mo content are composed of Al and Al3Ni phases.With the increase of Mo content,the skeleton size of porous structure was gradually refined,the specific surface junction increased,and the crystallinity decreased.However,the high content of Mo leads to the excessive refinement of the porous structure skeleton and the collapse of fracture.The hydrogen evolution overpotential at the current density of 100m A·cm-2 shows the law of decreasing first and then increasing with increasing Mo content.The prepared Ni2.5Mo2.5 alloy has the lowest hydrogen evolution overpotential and the maximum exchange current density,which is 218 m V and 0.29×10-3 A·cm-2.The process of hydrogen evolution is controlled by the Volmer-Heyrovsky step,and the polarization curve after 1000 cycles of cyclic voltammetry is basically the same.The overpotential increased by 3.67%at 50 m A·cm-2 current density,showing excellent hydrogen evolution stability.Subsequently,Ni/Ru O2 and Ni-Mo/Ru O2 composite electrodes were prepared by de-alloying combined with colloidal polysettization.The analysis results showed that Ru O2 phase existed in all three electrodes,and Ru O2 was coated on the surface of the porous skeleton due to polycondensation.The addition of Mo added the amorphization of the alloy and promoted the refinement of the pore size of the porous skeleton to form a bicontinuous nanostructure.porous structure.The addition of Mo and the increase of Mo content all improved the electrocatalytic hydrogen evolution performance.The nanoporous Ni2.5Mo2.5/Ru O2 composite electrode had the lowest hydrogen evolution overpotential in 1 mol·L-1 Na OH solution.The hydrogen evolution process was controlled by the Volmer-Heyrovsky step.The overpotential was 182 m V at a current density of 50 m A·cm-2,and the exchange current density was 0.31×10-3 A·cm-2.After over 1000 cycles of cyclic voltammetry,the overpotential was only Increased by 2.75%.Compared with Ni2.5Mo2.5 electrode,the performance of electrocatalytic hydrogen evolution was significantly improved. |
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