Controllable Preparation Of Ultra-thin Layer Nickel-iron Hydroxides And Their Electrocatalytic Oxygen Evolution Properties

The development of a new energy system with no/low carbon participation,（especially hydrogen energy）,which is a timely response to the major needs of the country and is also a high-quality solution to reduce carbon emissions and mitigate climate change.Electrolytic water technology is the most ideal green hydrogen production pathway.However,the oxygen evolution reaction（OER）at the anode of electrolytic water was limited by the four-electron transfer process and kinetic inertia,which limited the efficiency of hydrogen production from electrolytic water.Therefore,inexpensive,efficient,and stable OER electrocatalysts need to be developed to reduce the overpotential of the reaction and accelerate the OER reaction kinetics.Layered bimetal hydroxides（LDH）,especially NiFeLDH,has become the first choice for OER electrocatalysts due to its unique structure and good catalytic activity.But it has some problems such as low electronic conductivity and insufficiently exposed active sites hindered the further improvement of their OER activity and stability.Based on the above problems,in this paper,by optimizing the synthesis route of NiFeLDH,the influence of the synergistic regulation strategy of morphology and structure on the performance of OER was studied,so as to provide a reference for seeking practical high-efficiency electrocatalyst.The specific research content is as follows:1)Using the self-remodeling strategy of bimetallic alxide precursor,the ultra-thin crystalline phase-amorphous coupled w-Ni₃Fe₁-LDH was successfully prepared in a non-alkaline environment.It has abundant oxygen vacancies and a large specific surface area,which provides more efficient active sites.The electrochemical test showed that w-Ni₃Fe₁-LDH had excellent OER electrocatalytic activity,the corresponding overpotential was only 213 m V and 308 m V at the current density of 10 m A·cm^-2 and 50m A·cm^-2.Respectively,It had a low Tafel slope(80.5 m V·dec^-1)and showed good stability（20 h）.The results show that,comparing with the highly crystalline Ni₃Fe₁-LDH,the ultra-thin nanosheet morphology,the coupling structure of crystalline phase and amorphous phase,and the synergistic effect of oxygen vacancy defects enhance the electron transport ability of the material,increase the number of effective active sites exposed,and significantly reduce the reaction overpotential to achieve improved OER performance.In addition,this self-remodeling strategy is simple and environmentally friendly,which provides new ideas for the design and development of other functional materials.2)The two-dimensional（2D）composite heterogeneous materialα-Co（OH）₂/w-Ni₃Fe₁-LDH with good hydrophilia was prepared by co-precipitation method.The OER performance test showed that comparing withα-Co（OH）₂and w-Ni₃Fe₁-LDH,the composite catalyst had the best OER activity,and its overpotential was as low as 209 m V at 10 m A cm^-2.While the Tafel slope was also significantly reduced,and the stability of the catalyst was greatly improved.It could be maintained for 60 h at a current density of 10 m A·cm^-2.The results show that the introduction ofα-Co（OH）₂accelerated the electron transport rate of the composite heterogeneous material,reducing the energy barrier required for the reaction,improving the hydrophilic energy of the surface of w-Ni₃Fe₁-LDH,and enhanced the contact between the electrolyte and the electrode.Two-dimensional composite heterostructure of ultrathin nanosheets is also conducive to the release of gas,and improves the OER activity and stability of the catalyst.