Study On Electrochemical Catalytic Water Oxidation Based On Non-Precious Metal (Ni,Co) Catalysts

Hydrogen energy is a clean,pollution-free energy source with high energy density.It is an ideal alternative to traditional fossil fuels to solve energy shortage and environmental problems.Electrocatalytic water splitting is a simple,efficient and environmentally friendly way to produce hydrogen.Because water oxidation half-reaction involves the transfer of four electrons,and behaves slow kinetic process,which is a bottleneck in electrocatalytic water splitting reactions.Therefore,developing water oxidation catalysts?WOCs?with high catalytic activity is essential to realize the production of hydrogen by electrocatalytic water splitting with low-cost.Nickel and cobalt bimetallic oxides and hydroxides have received extensive attention because of their excellent catalytic water oxidation activity and low price.However,the low conductivity of metal oxides and hydroxides impedes the improvement of their water oxidation performance.In view of this,this paper improves the electrocatalytic water oxidation performance of nickel-cobalt bimetal oxides and hydroxides through morphological construction and combination with conductive materials.The details are as follows:?1?First,a C@NiCo₂O₄ catalyst with NiCo₂O₄ nanosheets coated on the outer surface of the carbon hollow microsphere was prepared via reflow,calcination,etching and other experimental methods,using SiO₂ as a sacrificial template.The C@NiCo₂O₄/NF electrode was obtained by loading C@NiCo₂O₄ onto a piece of nickel foam?NF?.The electrode exhibited excellent electrocatalytic performance,which reached a current density of 10 mA cm^-2 at the overpotential???of only 268 mV in 1 M KOH solution.Further studies have shown that the introduction of the hollow carbon microsphere not only accelerates the charge transfer of the catalyst enhancing its ability to transport electrons,but also provides a suitable three-dimensional morphology helping to expose more active sites.?2?Second,CuO nanowires were grown in situ on the copper foam?CF?by chemical oxidation and calcination.Then,the metal high conductive nickel layer was coated on the surface of CuO nanowires by electrodeposition.Finally,NiCo hydroxide nanosheets were vertically grown on the surface of nickel-coated CuO nanowires by a low temperature hydrothermal process?85??,and the NiCo/Ni/CuO/CF electrode was obtained.In 1 M KOH solution,the electrode required?of only 246 and 286 mV to reach a current density of 10 mA cm^-2 and 100 mA cm^-2,respectively,and exhibited a Tafel slope of 37.9 mV dec^-1,indicating its excellent catalytic water oxidation performance and fast reaction kinetics.In addition,the electrode can work stably for more than 60 h at a current density of 100 mA cm^-22 without performance degradation.Further studies have shown that this unique nanowire nanosheet structure containing a high conductive nickel layer not only enhances the electron transfer ability of the catalyst,but also exposes a large number of active sites.Moreover,each layer of this in-situ growth structure is closely combined,which is conducive to the long-term stable operation of the catalyst.