Preparation And Performance Study Of Nickel-based Ternary Metal Alkali Water Oxygen Evolution Catalyst

Water splitting to produce hydrogen is an emerging renewable energy conversion technology that can reduce the consumption of fossil energy and reduce carbon emissions.However,oxygen evolution involves a four-electron transfer,there are many reaction steps and the reaction process is complex,which greatly limits the overall efficiency of water splitting.The highly active electrode material can effectively promote the process of water splitting reaction and greatly reduce the voltage required to drive water splitting.Among them,nickel-iron-based hydrotalcite electrode materials exhibit excellent intrinsic activity,but the working time is short under high current,easy to inactivate,and the inactivation mechanism is not clear.Because of the above problems,the dynamic behavior of the surface active components of the electrode during water splitting is studied,the failure mechanism of the catalytic material is analyzed,and the OER activity and stability of the catalytic electrode are improved.（1）First,Ni Fe was deposited on a variety of carriers,and it was found that the OER activity of the composite electrode based on nickel foam was better.Then chromium is added to improve the catalytic activity and stability of the composite electrode.The introduction of Cr not only promotes the transformation of Ni Fe composites from spinel to Layered double hydroxides（LDH）,but also has a protective effect on Fe.Compared with binary Ni Fe hydroxide composites,ternary composites show better OER electrocatalytic activity in alkaline water,and by changing the Cr content,deposition time,and other conditions,it is found that when the Cr is 0.01 M and the deposition time is 1500 s,the Ni Fe Cr composite electrode prepared in 1 M KOH solution has an initial potential of only 1.46 V（vs.RHE）relative to the reversible hydrogen electrode,and the overpotential reaches the lowest,η₁₀is 233 m V,η₁₀₀is 268 m V,and its Tafel slope is 29.3m V·dec-1.Secondly,the OER polarization curve was tested on the electrolyzer,and the combined electrode can drive water decomposition at an operating voltage of 1.57 V.It is found that during the water-splitting process,the chromium in the composite is partially oxidized to Cr⁶⁺,and the electrons generated in this oxidation process will quickly accumulate near the iron site,resulting in local charges rearranging on the surface and enhancing catalytic activity.Through ICP-MS and EDS characterization,it is found that with the extension of the water decomposition reaction,the chromium metal content on the electrode surface will gradually decrease,the iron content attenuation will weaken,and the electronegativity of chromium ions is greater than that of iron ions,which is easier to release electrons,hindering the dissolution of iron in lye.so that the catalyst obtains excellent durability,and can run continuously for 200 h at a current density of 100m A·cm^-2,with almost no attenuation.（2）Ni Co/NF materials with nanoparticle structure were prepared on nickel foam by constant voltage electrodeposition.It was found that Ni Co/NF materials had the best synergy when the molar ratio Ni:Co=8:2,and the overpotential of Ni_0.8Co_0.2/NF electrode was only 243 m V at a current density of 10 m A·cm^-2.Then,the catalyst surface is reconstructed by three electrochemical activation methods,CV,which can generate nanosheet cluster morphology,IT causes the disappearance of small nanoparticles on the surface of the material,CP can generate a hollow trumpet-like structure,and activation can improve the catalytic performance of the electrode.By improving the OER performance of Ni_0.8Co_0.2/NF by Ce doping,the deposited metal cerium will be spontaneously oxidized to cerium oxide in the air,which not only does not change the initial structure of the catalyst but also increases the specific surface area of the material.When Ce doped is0.01 M,the intrinsic overpotential of Ni_0.8Co_0.2Ce_0.1/NF is 215 m V.Then,by adjusting the p H and deposition time,the catalytic activity of the catalyst was continuously improved,and the overpotentialη₁₀of the Ni_0.8Co_0.2Ce_0.1/NF-600s electrode was 207 m V.In the 1M KOH environment,after 36 hours of continuous electrolysis of water at high current,the catalytic activity of the electrode has almost no attenuation.