A General "In Situ Etch-Adsorption-Phosphatization" Strategy for the Fabrication of Metal Phosphides/Hollow Carbon Composite for High Performance Liquid/Flexible Zn-Air Batteries

Abstract

Benefiting from the admirable energy density (1086 Wh kg^-1 ), overwhelming security, and low environmental impact, rechargeable zinc-air batteries (ZABs) are deemed to be attractive candidates for lithium-ion batteries. The exploration of novel oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) bifunctional catalysts is the key to promoting the development of zinc-air batteries. Transitional metal phosphides (TMPs) especially Fe-based TMPs are deemed to be a rational type of catalyst, however, their catalytic performance still needs to be further improved. Considering Fe (heme) and Cu (copper terminal oxidases) are nature's options for ORR catalysis in many forms of life from bacteria to humans. Herein, a general "in situ etch-adsorption-phosphatization" strategy is designed for the fabrication of hollow FeP/Fe₂ P/Cu₃ P-N, P codoped carbon (FeP/Cu₃ P-NPC) catalyst as the cathode of liquid and flexible ZABs. The liquid ZABs manifest a high peak power density of 158.5 mW cm^-2 and outstanding long-term cycling performance (≈1100 cycles at 2 mA cm^-2 ). Similarly, the flexible ZABs deliver superior cycling stability of 81 h at 2 mA cm^-2 without bending and 26 h with different bending angles.

Keywords: Fe─P/Cu3P-NPC; heterogeneous interfaces; in situ etch-adsorption-phosphatization; liquid/flexible Zn-Air batteries; synergistic effects.