Preparation Of Transition Metal (Ni,Co,Cu) Nitrate Hydroxides For Electrocatalytic Oxygen Evolution

Electrocatalytic water splitting can achieve the conversion of electrical energy to chemical energy and there is no pollutant in the process,which is considered as one of the effective strategy to obtain hydrogen and solve environmental pollutions and energy crisis.However,as one of the half reactions of water splitting,the oxygen evolution reaction?OER?involves the transfer of four electrons,which is slow in kinetics,limiting the rate of electrocatalytic water splitting and its practical application.Therefore,it is necessary to develop an efficient and stable OER electrocatalyst to promote the water oxidation efficiency.In recent years,metal carbonate hydroxides materials have shown great performance in the field of electrocatalysis,such as electrocatalytic OER.On this basis,how to broaden the types of basic salt materials,simplify the experiment process,and further improve the catalytic performance of the materials is worth exploring.Herein,transition metal nitrate hydroxide/nickel foam?MNH/NF,M=Ni,Co,Cu?composites were designed and synthesized.To modify it,Fe?OH?₃ was introduced and a series NiNH@Fe?OH?₃/NF materials were obtained.The electrocatalytic OER properties of these two materials were further studied.The MNH/NF composite with three-dimensional structure was prepared by one-step molten salt method.Among all these samples,NiNH/NF exhibits the best OER activity in alkaline solution with a low overpotential of 231 mV vs.reversible hydrogen electrode?RHE?to achieve a geometrical current density of 50 mA/cm² and a low Tafel slope of81 mV/dec.And although MNH is converted to metal oxyhydroxide?for NiNH and CoNH?or oxide?for CuNH?as likely the real active species,it still has excellent stability and durability,which can be attributed to the morphology and structural integrity of MNH/NF after OER process.The MNH electrocatalyst with great intrinsic catalytic activity and stability can be prepared by a very economical and simple method,which can be applied to energy conversion and storage.Furthermore,the NiNH/NF material was modified by interfacial hydrolysis reaction,and NiNH@Fe?OH?₃/NF composite was obtained.The Fe?OH?₃ produced through hydrolysis reaction preferentially grown in situ on the surface of NiNH nanowires to form a NiNH@Fe?OH?₃ core-shell structure.The synergy at the interface of NiNH and Fe?OH?₃ is beneficial to the OER performance of the material.Adjusting the reaction time can effectively control the amount of Fe?OH?₃,thereby further regulating the OER catalytic performance of the samples.When the reaction time is one day,the obtained NiNH@Fe?OH?₃/NF D1 sample performs best,and requiring only an ultra-low overpotential of 200 mV vs.RHE at 50 mA/cm² with a Tafel slope of 49 mV/dec and the stability of NiNH@Fe?OH?₃/NF material is also excellent.