Electric field-induced phosphorization to prepare CoP@Biochar composites for efficient bifunctional oxygen electrocatalysis

Abstract

The large-scale use of zinc–air batteries (ZABs) has been limited by their sluggish OER and ORR kinetics. The current synthesis of catalysts for air electrodes requires harsh conditions. The design and manufacture of bifunctional catalysts under mild conditions are of great significance. Herein, an electric field-induced phosphorization at room temperature is proposed to prepare bifunctional electrocatalysts designed by coupling N-doped carbon and CoP nanoparticles based on a multi-active site-integration strategy. The simple, safe, non-toxic and highly controllable electric field-induced reaction creates CoP active sites. The catalyst exhibits a remarkably narrow potential gap (ΔE) of 0.65 V between the half-wave potential of the ORR and the potential of the OER. The low ΔE signifies a superior catalytic bifunctionality of CoP@NWC. Aqueous ZABs with an optimized catalyst achieve a high discharge specific capacity of 805.8 mA h g_Zn⁻¹ and long-term cycling stability over 1200 cycles. Quasi-solid-state ZABs show a discharge-specific capacity of 760.5 mA h g_Zn⁻¹. The outstanding bifunctional catalytic activities originate from the synergistic effect of dual active sites between CoP and NWC induced by the electric field. This work provides a new perspective for building advanced catalysts from biomass under ambient conditions.