Phase‐Controlled Cobalt Phosphide Nanoparticles Coupled with N, P, S Co‐Doped Hollow Carbon Polyhedrons As Efficient Catalysts for Both Alkaline and Acidic Hydrogen Evolution

Tailoring cobalt phosphide electrocatalysts with a tunable phase and morphology is of great importance for the advancement of hydrogen evolution reaction (HER). The synthesis of phase‐ and morphology‐modulated hollow cobalt phosphide nanoparticles coupled with N, P, S co‐doped carbon (Co‐P@NPS‐C) polyhedrons through a facile three‐step method is reported. Benefiting from the cooperation of structural features, heteroatoms doping, and catalytic components (CoxP, a mixture of CoP and Co2P), the hollow CoxP@NPS‐C polyhedrons exhibit superior HER performance and long‐term stability in 1.0 m KOH solution, with a low onset potential value (18 mV), an overpotential of 80 mV at 10 mA cm−2, and a small Tafel slope of 57.6 mV dec−1. In addition, the CoxP@NPS‐C electrodes exhibit good electrochemical properties and stability in 0.5 m H2SO4 solution. These results suggest a novel and promising coating approach with poly(cyclotriphosphazene‐co‐4,4′‐sulfonyldiphenol (PZS) to fabricate other heterogeneous catalysts for various applications.