Preparation And Performance Of Co-Ni Hydroxides For Eletro-Catalytic Oxygen Evolution

The rate and efficiency of many important chemical and energy conversion processes are often limited by the electro-catalytic oxygen evolution reaction(OER).The research and development of efficient,mineral-rich and inexpensive OER catalysts is one of the important directions of the water oxidation field.Faced with these problems,a series of studies are developed for the preparation of Co2Ni(OH)x catalyst and its OER properties.Amorphous Co-Ni hydroxide(Co2Ni(OH)x)is prepared by the method of ultrasonic-bath coprecipitation at room temperature using CoCl2,NiCl2 and Na3C6H5O7(TSC)as complexing agent.Electro-catalytic oxygen evolution reaction activity and stability under alkaline condition of the catalyst material are investigated by linear potential scanning,chronopotentiometry et al.We determine five factors that can affect the water oxidation activity,contain mole ratio of Co and Ni,temperature,TSC,ultrasonic during the preparation,coprecipitation.It turns out that Co-Ni hydroxide has best oxygen evolution performance,which prepared with a Ni and Co mole ratio of 2:1,preparation temperature 20.0 ℃ and TSC addition using ultrasonic coprecipiation method.As a result,the current density J is as high as 29.87 mA/cm2(E = 0.900 V vs.HgO/Hg).It can efficiently catalyze OER under alkaline condition with a current density of 10.00 mA cm-2 at an overpotential of 431 mV,exhibits favorable kinetics toward the OER with a Tafel slope of 79.70 mV/dec.The material’s OER performance even surpasses the precious metal IrO2 when the loading is the same.It also has good stability in alkaline electrolyte,maintains its activity(20 mA cm-2)for at least 8000 s.At η = 431 mV,the mass activity value(MA)is 66.67 A/g,the turnover frequency value(TOF)is 0.03928 s-1,the electric double layer capacitor value(Cdl)is 2415 μF/cm2,and the surface roughness facfor(Rf)is 40.25.With the structural and component characterization results of filed emission scanning electron microscopy,energy dispersive spectroscopy,X-raydiffraction,Fourier transform infrared spectroscopy,Raman spectrum,X-ray photoelectron spectroscopy at al,the catalyst with optimal conditions has a granular structure,the ratio between Co and Ni is close to 2:1,and the composition is Co2Ni(OH)x.The reasons for good OER performance of the catalyst are the amorphous structure,enough Ni2+/Ni3+ and Co2+/Co3+ OER-catalytic active sites,the synergistic effect between Co and Ni metal ions,low electrocatalytic oxygen evolution charge resistance and large electrocatalytic activity area.All the results prove that the amorphous Co2Ni(OH)x fabricated by room-temperature ultrasonic coprecipitation method not only has a facile,green and environmental protection route,but also has a good activity even surpassing the the precious metal IrO2,it is a kind of electrocatalytic material which owns high quality and cheap characteristics.