Rational design of porous Ni-Co-Fe ternary metal phosphides nanobricks as bifunctional electrocatalysts for efficient overall water splitting

Precise control is critically significant for synthesizing highly efficient bifunctional water splitting electrocatalyst. This study has developed a facile strategy for fabricating porous Ni-Co-Fe ternary metal phosphides nanobricks (denoted as Ni-Co-Fe-P NBs) with specified components and morphology. The optimized sample of Ni-Co-Fe-P NBs showed remarkable electrocatalytic performance in 1.0 M KOH. When served as bifunctional electrocatalyst for overall water splitting, the Ni-Co-Fe-P NBs required a low cell voltage of 1.46 V to achieve a current density of 10 mA cm−2 along with superior durability. Density functional theory (DFT) calculation revealed that the homogeneously distributed Ni and Fe can optimize ∆GH*, and therefore enhance their HER activity. In the case of OER, introducing Ni, Fe and P can promote the formation of desired Co4+ sites and stabilize O-containing intermediates (H*, OH*, OOH*) on the surface of the catalysts.