A dual-confinement strategy to construct cobalt-based phosphide nanoclusters within carbon nanofibers for bifunctional water splitting electrocatalysts

Abstract

It is a challenging task to explore highly active and stable noble-metal-free bifunctional electrocatalysts for water splitting, both in hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Herein, a new dual-confinement strategy for the fabrication of cobalt-base phosphide in the carbon nanofibers (CNFs) was proposed via electrospinning, followed by the corresponding pyrolysis. The ultrafine phosphides derived from the pore confinement of ZIF and space confinement of the polymer revealed abundant active sites and P defects. More importantly, by introducing a second metal element Ni or Cu, the electronic structure and synergistic effect were further enhanced, and the obtained bimetallic CoNiP_x–CNF electrocatalyst exhibited the remarkable performance for HER and OER, featuring the low η₁₀ values of 154 and 269 mV in 1.0 M KOH electrolyte, respectively. CoNiP_x–CNFs as a catalyst for both anode and cathode showed a current density of 10 mA cm⁻² at a voltage of 1.56 V, exceeding better stability, which is superior to most non-noble metal electrocatalysts reported in a previous research. The dual-confinement strategy is believed to provide an effective and simple approach for the synthesis of high-performance and cost-efficient bifunctional electrocatalysts for overall water splitting.