Prussian blue analogue-derived Co-Ni5P4 porous nanosheet arrays composite coal-based carbon nanofibers as efficient self-supported electrocatalyst for overall water splitting

The development of economical, earth-rich, and high-performance transition metal phosphides electrocatalysts is crucial for water splitting. Herein, the NiCo PBA/Ni(OH)2 hierarchical nanostructure arrays are in situ grown on the coal-based carbon nanofibers (C-CNFs) using hydrothermal and co-precipitation methods. Subsequently, the Co-doped Ni5P4 porous nanosheet arrays composite coal-based carbon nanofibers electrocatalyst (Co-Ni5P4@C-CNFs) is obtained through low-temperature phosphorization process. Benefiting from cation-doped, porous nanosheet arrays structure and self-supported conductive substrates, the Co-Ni5P4@C-CNFs has excellent electrocatalytic performance for overall water splitting. It provides low overpotentials of 75 mV for hydrogen evolution reaction (HER) and 231 mV for oxygen evolution reaction (OER) to achieve the current density of 10 mA cm−2 in 1 M KOH electrolyte. Furthermore, the Co-Ni5P4@C-CNFs demonstrates a low overall water splitting cell voltage of 1.537 V at current density of 10 mA cm−2 and remarkable long-term stability for over 160 h. It outperforms the most transition metal phosphide bifunctional electrocatalysts reported to date. This research provides a novel strategy for synthesizing high-performance transition metal phosphides bifunctional electrocatalysts.