关键词: ZIF-67, 氧还原反应, 氧析出反应, 锌空气电池, 非贵金属催化剂

Abstract:

Rechargeable zinc-air batteries have gradually attracted much attention worldwide due to their high capacity, high energy density and low price. Oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) correspond to the charging and discharging processes in rechargeable zinc-air battery, respectively. At present, commercial Pt/C and IrO₂ catalysts hinder the large-scale application of zinc-air batteries due to low reserves, high prices and poor stability. Therefore, exploring high performance, low cost and high stability with dual functional catalysts is important for the development of rechargeable zinc-Air batteries. The metal-organic frameworks (MOFs) have high specific surface area, structural stability, good catalytic activity and application prospects. Transition metals have high catalytic activity, but they are easily corroded in alkaline solutions. Non-metallic materials are inexpensive and have catalytic activity under a specific structure. Taking the advantages of the above-mentioned materials, ZIF-67 was used as the precursor, along with heteroatom doping and high temperature heat treatment to prepare a porous carbon material FeNi-CoP/NC containing multiple transition metals and non-metal particles as a zinc-air battery catalyst. Physical and chemical characterizations, and catalytic performance testing of the catalyst were carried out by SEM, XRD, XPS and electrochemical methods, and finally assembled into a full battery for charge and discharge performance experiments. The results showed that the prepared FeNi-CoP/NC catalyst had rhombohedral dodecahedron structure and specific surface area of 402 m²·g^-1. The half-wave potential went up to 0.83 V when used as an electrocatalyst for oxygen reduction reaction in zinc-air batteries. After 5000 cycles, the current density only lost 5.06% and the half-wave potential changed little, revealing a good stability; the overpotential of OER was 290 mV at the current density of 10 mA·cm^-2. And the catalyst could be kept stable for 12 h at 100 mA·cm^-2. The performance test of the full battery demonstrated that the peak power density was as high as 150 mW·cm^-2, and a narrow potential gap of 0.6 V was maintained at the current density of 3 mA·cm^-2. The good catalytic activity might be mainly attributable to the fact that doping with multiple metal elements can provide rich valences to accelerate the four-step coordinated proton/electron transfer step, and the good conductivity of CoP also effectively improves the catalytic activity of FeNi-CoP/NC. This work provides useful guidance for improving the electrocatalytic performance of the catalyst through simple doping and heat treatment strategies.

Key words: ZIF-67, Oxygen reduction reaction, oxygen evolution reaction, Zinc-air battery, Non-precious metal catalyst