Ultrafine Co₂P nanoparticles encapsulated in nitrogen and phosphorus dual-doped porous carbon nanosheet/carbon nanotube hybrids: High-performance bifunctional electrocatalysts for overall water splitting

The development of active, robust, and nonprecious electrocatalysts for both the oxygen evolution reaction and hydrogen evolution reaction (OER and HER) is highly crucial and challenging. Herein, ultrafine Co₂P nanoparticles (NPs) encapsulated in nitrogen and phosphorus dual-doped porous carbon nanosheet/carbon nanotube hybrids are prepared via a straightforward pyrolysis method. Impressively, the hybrids exhibit remarkable catalytic performance for both the OER and HER in 1.0 M KOH solution, with a current density of 10 mA cm^-2 at low over-potentials of 280 mV for the OER and 154 mV for the HER, respectively. More importantly, when fabricated as an alkaline electrolyzer, the hybrids afford 10 mA cm^-2 at a cell voltage of 1.64 V with strong stability, rivalling the integrated performance of a commercial IrO₂ and Pt catalyst couple. The achieved ultrahigh catalytic performance can be attributed to the nitrogen and phosphorus dual-doped carbon nanosheets, carbon-encapsulated ultrafine Co₂P NPs, high conductivity of incorporated carbon nanotubes, large surface area (199.94 m² g^-1), interpenetrated macro-/mesoporous structure, and the strong synergistic effect among these factors.