Effect of Phase Composition of the Hybrid Electrocatalysts Based on Nickel Phosphides and N,P-Doped Carbon on the Activities in the Processes of Hydrogen and Oxygen Evolutions From Water

The effect of the formation temperature of the composites based on Ni phosphides and N,P-doped carbon (Ni_xP_y/N,P-C) obtained by pyrolysis of a mixture of H₃PO₄-doped polyaniline and Ni(II) salt on their phase composition and electrocatalytic properties in the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) has been established. It is shown that increasing the pyrolysis temperature from 800 to 900 and 1000°C leads to an increasing in the content of the Ni₂P phase in the composites with simultaneously Ni₁₂P₅ decreasing and NiP eliminating. It is found that the highest activity in HER in an acidic electrolyte, as well as in OER, is inherent to Ni_xP_y/N,P-C formed at 900°C (with a close ratio of Ni₂P and Ni₁₂P₅ particles). The best performance in HER in an alkaline electrolyte is revealed by the obtained at 800°C analogue with dominant NiP particles and the highest N,P-doping level of the carbon.