Amorphous Bimetallic Phosphate–Carbon Precatalyst with Deep Self-Reconstruction toward Efficient Oxygen Evolution Reaction and Zn–Air Batteries

Abstract

Amorphous transition-metal compounds (a-TMC) have attracted more and more attention due to their high electrocatalytic activity for the oxygen evolution reaction (OER). However, it is still a challenge to in situ synthesize a-TMC-carbon nanocomposites at elevated temperature and figure out the exact advantages of the amorphous structure. Here, an amorphous iron-doped nickel phosphate–carbon hollow nanocomposite (a-NiFePO-C) has been simply prepared by coprecipitation of metal ions and phytic acid, followed by a controllable annealing process. The results show that a-NiFePO-C can achieve a low overpotential of 268 mV at 10 mA/cm2 and maintain 91.3% of the initial current density after a 9 h chronoamperometry test in a 1 M KOH solution with low mass loading of 0.1 mg/cm2. The excellent performance of a-NiFePO-C is attributed to the low charge-transfer resistance, bulk self-reconstruction, and synergetic oxidation of the bimetallic sites during cyclic voltammetry (CV) activation, resulting in the formation of a highly OER-active Fe(III)-Ni(oxy)hydroxide-carbon nanocomposite. Moreover, the rechargeable Zn–air batteries powered by the a-NiFePO-C + Pt/C electrode can present a lower charging voltage and superior cycle performance than that powered by a commercial RuO2 + Pt/C electrode.