Phosphorus-Doped FeNi Alloys/NiFe2O4 Imbedded in Carbon Network Hollow Bipyramid as Efficient Electrocatalysts for Oxygen Evolution Reaction

Ni/Fe-based bimetallic nanoarchitecture materials play an important role in the development of non-precious-metal-based electrocatalysts toward water splitting, but the low activity and poor stability greatly hinder their commercial applications. It is significant to explore facile and effective methods to improve their electrocatalytic activity. A simple self-template strategy is demonstrated to fabricate a hollow bipyramid constructed by P-doped FeNi alloys/NiFe2O4 nanoparticles encapsulated in carbon network (P-Ni0.5Fe@C). Bimetallic analogous MIL-101 (Fe) precursor (Ni0.5Fe-BDC CP) with uniform morphology and stable structure was synthesized through a solvothermal reaction. By subsequent carbonization and phosphorization steps, P element was doped into the composite FeNi alloys/NiFe2O4 nanoparticles. Benefiting from the efficient mass and electron transfer of the hollow structure, the precise adjustment for the electron structure of P dopants, and carbon-encapsulated active components that could provide large numbers of active sites as well as prevent the aggregation and dissolution of active components, the optimal P-Ni0.5Fe@C catalyst exhibits a low overpotential of 256 mV to reach a current density of 10 mA cm–2, a small Tafel slope of 65 mV dec–1, and remarkable long-term stability toward oxygen evolution reaction in 1 M KOH, which is better than that of commercial IrO2 (318 mV at 10 mA cm–2 for overpotential and 120 mV dec–1 for Tafel slope, respectively). More remarkably, when it was employed in a two-electrode configuration based on P-Ni0.5Fe@C as anode and commercial Pt/C as cathode catalysts (P-Ni0.5Fe@C || Pt/C), a potential of only 1.49 V (corresponding overpotential of 260 mV) was required to achieve 10 mA·cm–2. This work provides insight into the rational composition and morphology design of an earth-abundant electrocatalyst with highly efficient electrocatalytic activities toward overall water splitting.