In-situ formation of cobalt phosphide nanoparticles confined in three-dimensional porous carbon for high-performing zinc-air battery and water splitting

The rational design of efficient and stable carbon-based electrocatalysts for oxygen reduction and oxygen evolution reactions is crucial for improving energy density and long-term stability of rechargeable zinc-air batteries (ZABs). Herein, a general and controllable synthesis method was developed to prepare three-dimensional (3D) porous carbon composites embedded with diverse metal phosphide nanocrystallites by interfacial coordination of transition metal ions with phytic acid-doped polyaniline networks and subsequent pyrolysis. Phytic acid as the dopant of polyaniline provides favorable anchoring sites for metal ions owing to the coordination interaction. Specifically, adjusting the concentration of adsorbed cobalt ions can achieve the phase regulation of transition metal phosphides. Thus, with abundant cobalt phosphide nanoparticles and nitrogen- and phosphorus-doping sites, the obtained carbon-based electrocatalysts exhibited efficient electrocatalytic activities toward oxygen reduction and evolution reactions. Consequently, the fabricated ZABs exhibited a high energy density, high power density of 368 mW cm−2, and good cycling/mechanical stability, which could power water splitting for integrated device fabrication with high gas yields.