Cobalt-doped basic iron phosphate as bifunctional electrocatalyst for long-life and high-power-density rechargeable zinc-air batteries.

High-efficient and long-cycle air cathodes are crucial for the development of rechargeable zinc-air batteries (ZABs). Herein, we develop a strategy of micro-spherical cobalt-doped Fe 5 (PO 4) 4 (OH) 3 ·H 2 O (Co-FPOH), synthesized by a novel water-oil two-phase hydrothermal method, which was used as ORR/OER bifunctional electrocatalyst for ZABs. The change of local electronic distribution is identified by doping of Co into Fe 5 (PO 4) 4 (OH) 3 ·H 2 O (FPOH), effectively improving the electrocatalytic performance of the resulted Co-FPOH. The OER overpotential of Co-FPOH (290 mV) far outperforms state-of-the-art RuO 2 (350 mV); the ORR catalytic reaction of Co-FPOH is near 4e-, almost reaching the theoretical value of Pt/C (n = 4.00). The ZAB assembled with Co-FPOH as an air electrode exhibits an ultralong cycling lifetime of 450 h at 5 mA cm−2, a super high peak power density of 167.8 Wh cm−2, a high open circuit voltage of about 1.42 V and a large discharge specific capacity of 817 mAh g Zn −1 at 10 mA cm−2. The proposed Co-FPOH is expected to outperform precious metal electrocatalysts as a potential bifunctional electrocatalyst for advanced ZABs. Also, this work offers a novel strategy to synthesize excellent bifunctional electrocatalysts for this kind of energy-related electrocatalytic reactions. [Display omitted] Bifunctional electrocatalyst of Co-FPOH was synthesized by a novel water-oil two-phase hydrothermal method, which exhibited a long-cycle stability of up to 450 h at a current density of 5 mA cm−2 and a super high power density of 167.8 mW cm−2. ● A strategy of Co-FPOH is designed for ORR/OER bifunctional electrocatalyst. ● The local electronic distribution contributes to high-efficient electrocatalysis. ● ZABs assembled with Co-FPOH demonstrate excellent electrochemical performances. [ABSTRACT FROM AUTHOR]