Enhancing Water Splitting Performance via NiFeP-CoP on Cobalt Foam: Synergistic Effects and Structural Optimization

Hydrogen energy holds great promise for alleviating energy and environmental issues, with alkaline electrochemical water splitting being a key approach for hydrogen production. However, the high cost and limited availability of noble-metal catalysts hinder its widespread application. This study presents a novel method to fabricate a NiFeP-CoP/CF electrode. By growing CoOOH nanosheets on Co foam at low temperatures and filling the gaps between nanosheets with Ni and Fe phosphides, the prepared electrode exhibits outstanding electrocatalytic performance. For the oxygen evolution reaction (OER) in alkaline media, it requires overpotentials of only 235 mV and 290 mV to reach current densities of 10 mA cm^-2 and 100 mA cm^-2, respectively. In the case of the hydrogen evolution reaction (HER), overpotentials of 89 mV and 172 mV are needed to achieve current densities of -10 mA cm^-2 and -100 mA cm^-2. The NiFeP-CoP/CF-based electrolytic cell requires a cell voltage of only 1.70 V to achieve a current density of 100 mA cm^-2 for overall water splitting. Moreover, during long-term continuous operation at 100 mA cm^-2, the overpotential for OER remains constant while that for HER decreases. The low-temperature growth of CoOOH nanosheets on Co foam provides a new strategy for large-scale electrode production applicable in electrochemical processes and pollutant degradation. Significantly, filling the nanosheet gaps with phosphides effectively enhances the electrocatalytic performance of the system. This work offers a facile and cost-effective technique for the large-scale production of metallic (oxyhydr)hydroxides for electrocatalytic water splitting, showing great potential for industrial applications.