Fabrication of grass-like FeCoNiP/copper foam electrodes via cyclic voltammetry toward efficient overall water splitting reaction

Abstract

Exploration of electrocatalysts with excellent activity and durability, facile scale-up and low cost is one of the most crucial issues for water splitting. Ternary FeCoNi phosphides were obtained by electrodeposition of FeCoNi hydroxides on copper foam (CF) via cyclic voltammetry and followed by low-temperature phosphorization. Benefiting from synergistic effects between simultaneous presence of multi-metallic active centers and three-dimensional substrate of copper foam, FeCoNiP/CF exhibits an ultralow overpotential of 48 mV for hydrogen evolution reaction (HER) and 228 mV for oxygen evolution reaction (OER) to deliver a current density of 10 mA cm−2 in 1.0 M KOH solution, and its Tafel slopes are respectively 93.46 and 87.84 mV dec−1 for HER and OER, indicating outstanding electrocatalytic activity as a bifunctional electrocatalyst. An electrolyzer assembled by this catalyst demonstrates cell voltages of 1.52 and 2.08 V at current densities of 10 and 200 mA cm−2, respectively. Remarkably, the durability of FeCoNiP/CF measured by chronoamperometry test can maintain 96.4% after 120 h, indicating excellently long-term stability. The performances of FeCoNiP/CF are much better than those of FeCoNiP powder catalyst obtained by hydrothermal-phosphorization and other bimetallic phosphides, due to its uniquely grass-like morphology and synergetic effects of various metallic active centers. This research can provide an effective strategy of mass production of electrodes with prominent catalytic activity and stability for overall water splitting reaction.