Design And Performance Of Mo-Ni Based Electrocatalysts For Overall Water Splitting

Under the current situation of human energy crisis,the development of new energy is imminent.Hydrogen energy has gradually attracted people's attention due to its excellent advantages.Research on cheap catalysts is the key to the large-scale use of hydrogen energy.Based on molybdenum and nickel elements,the main content of this paper is to obtain high-performance catalysts through the combination of different molybdenum and nickel and the method of regulating morphology.Molybdenum carbide is widely used in catalysts because of its unique characteristics of metal and conductivity,but its catalytic performance is not very prominent,so it is very meaningful to develop high-performance molybdenum carbide-based catalysts.It is found that nickel ion has a strong ability of water decomposition and molybdenum has a strong ability of hydrogen adsorption.The combination of the two can effectively promote the performance of electrolytic water.Molybdenum and nickel were successfully adsorbed on the glucose carbon sphere in the ratio of 2:1 by adsorption method,and then carbonized at high temperature.The hydrogen evolution performance of Ni/Mo₂C-CS at 10 mA/cm² was greatly improved,which was obviously better than that of pure Ni and Mo₂C,and the oxygen evolution performance was also improved.When catalyst is grown on nickel foam,it can prevent agglomeration between particles,thus increasing the contact area between catalyst and electrolyte.But Nickel foam due to its poor hydrophilicity,the size of the particles formed after hydrothermal is not uniform,which is not conducive to the application of the catalyst.so we use nickel oxide for its high hydrophilicity and ammonium fluoride to cause the current collector to produce more active sites with increased adhesion to prepare 2D ultrafine Mo-based precursor nanosheets with uniform dimensions and a stable structure on nickel foam?NF?.Further phosphorization treatment is performed to obtain porous molybdenum phosphide?MoP?nanosheets on Ni₃P/NF.As a freestanding integrated electrode,MoP@Ni₃P/NF possess excellent catalytic activity for the HER and OER with low overpotentials?45 mV to reach 10 mA/cm² for the HER and 331 mV to reach35 m/cm² for the OER?.The activity as both an anode and cathode catalyst for overall water splitting can reach 1.67 V at 10 mA/cm².The oxide layer on the surface of the calcined foamed nickel increases the hydrophilicity of the foamed nickel and provides a large number of nucleation sites for the growth of the catalyst.The uniformly sized nanosheets formed after hydrothermal increase the external specific surface area of the material,so the number of active sites of the catalyst increased,and the electrocatalytic performance was greatly improved.Combining the above experimental results,we found that the oxygen evolution performance of the above experimental catalysts still has a certain gap compared with the best oxygen evolution catalysts currently available,and the poor OER performance often limits the development of the catalyst in the direction of overall water splitting,so in this study,prussian blue analogue?PBA?is grown in-situ on molybdenum-based nanosheet spheres by a simple and ingenious method and then subjected to phosphorization.The resulting composite catalyst exhibits highly efficient overall water splitting performance,overpotentials at current densities of 10 mA/cm² and 100mA/cm² for the HER and OER are 61 mV and 268 mV,respectively.Moreover,an alkaline electrolyzer makes up by the catalyst both as positive and negative can reach a cell voltage 1.494 V at 10 mA/cm² for the overall water splitting.PBA is anchored to the substrate in the way of in-situ growth,which can not only increase the specific surface area of the material and increase the active site of the catalyst,but also firm contact can increase the electron transport rate,as well as the higher oxygen evolution of PBAs itself.The oxygen evolution performance greatly improves after the PBAs grown in situ.