Embedding Fe2P nanocrystals in bayberry-like N, P-enriched carbon nanospheres as excellent oxygen reduction electrocatalyst for zinc-air battery

Transition metal phosphide/carbon composites are promising electrocatalysts for oxygen reduction reaction (ORR). Herein, we propose a facile process to fabricate a bayberry-like N, P-enriched carbon nanospheres embedded with Fe 2 P nanocrystals (Fe 2 P/NPCs). Bayberry-like polyaniline nanospheres (PANI-NS) are firstly synthesized through microemulsion template method . Then, Fe is incorporated in PANI-NS during the hydrothermal treatment . Lastly Fe x P nanocrystals and N, P-enriched carbonaceous carriers are obtained by pyrolyzing the hydrothermal-treated PANI-NS. The resultant Fe x P/NPCs exhibit a uniform particle size (~250 nm), a large specific surface area (523 m 2  g −1 ) and a homogeneous mesoporous structure (~3.46 nm). The phase structure of Fe x P depends on the Fe/P (molar ratio) during hydrothermal treatment. When Fe/P is around 0.2, a preferable Fe 2 P phase is obtained. The Fe 2 P/NPCs exhibit outstanding ORR electrocatalytic activity with a half-wave potential of 0.820 V (vs. RHE) and a diffusion-limited current density of 5.58 mA cm −2 , comparable with commercial Pt/C. Moreover, Fe 2 P/NPCs possess a good duration stability and higher methanol tolerance than commercial Pt/C. When assembled in zinc-air batteries, Fe 2 P/NPCs contribute to an open circuit voltage of 1.449 V, a maximum power density of 128.38 mW cm −2 , and a specific capacity of 691.0 mAh g −1 , superior to the commercial Pt/C-based zinc-air battery.