Tuneable and coral-like NiCoP for enhanced oxygen and hydrogen evolution reaction

Abstract

Meticulous tuning of nonprecious catalysts for overall water splitting is highly challenging but it is one of the most promising routes toward the future hydrogen economy. Here, we present a highly active, robust and earth abundant NiCoP electrocatalyst with a tuning capacity to excel in both oxygen and hydrogen evolution reactions. The composition of Ni and Co has been varied in a facile two-step method to produce coral-like NiCoP. The variant Ni0.25Co0.75 P has shown remarkable OER activity with overpotential as low as 240 mV at 10 mA/cm2 current density and Tafel slope of 68 mV dec−1 in alkaline medium. On the other hand, Ni0.75Co0.25P exhibited commendable HER performance with an overpotential of 120 mV and a Tafel slope of 123 mV dec−1 in an acid medium. Long-term durability and minimal loading of the catalyst ascertain the significance of the present catalyst. Moreover, our theoretical study finds that NiCoP provides a much higher electron density of d-states near the Fermi level compared to the individual metal phosphide and the low-index surface (100) of composite phosphide has a moderate level of desorption energy of oxygen and hydrogen compared to that of NiP2 & CoP corroborating the superiority of NiCoP in OER/HER performance.