Design and construction of 3D porous hierarchical structure Ni–Fe–Co bifunctional catalyst toward highly efficient overall water splitting

Developing high performance, cost-effective, non-precious metal electrocatalysts for overall water splitting (OWS) still remains a serious challenge. Heterostructures comprised of multiple metals possess significant potential to enhance OWS owing to the prominent synergistic effects between different components. Herein, we successfully fabricated NiFeCoPSO and Co(OH)₂/NiFeSO structures with a three-dimensional (3D) porous hierarchical structure, using carbon cloth (CC) as a substrate. The innovative 3D hierarchical structure ensures that numerous active sites are extensively exposed, thus guaranteeing competent contact between the active reaction centers and the reactant. As a result, the obtained NiFeCoPSO displays outstanding hydrogen evolution reaction (HER) ability (102 mV for a current density of 10 mA cm⁻²), while the intermediate product Co(OH)₂/NiFeSO exhibits excellent oxygen evolution reaction (OER) performance (231 mV for 10 mA cm⁻²). Furthermore, the dual electrode system assembled using NiFeCoPSO cathode and Co(OH)₂/NiFeSO anode presents excellent overall water splitting (OWS) behavior (1.55 V for 10 mA cm⁻²). This research offers a cost-effective transition metal phosphide-sulfide electrocatalyst and its synthesis method for OWS.