Preparation of FeNi-CoP/NC Bifunctional Catalyst and Study on Its Electrocatalytic Performance
Rechargeable zinc-air batteries have gradually attracted people's attention due to high capacity, high energy density and low price. Oxygen reduction reaction(ORR) and oxygen evolution reaction(OER) respectively correspond to the two processes of rechargeable-zinc-air battery charging and discharging and improving its reactivity is helpful to the use of the batteries. 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 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. Based on the advantages of the above-mentioned materials, ZIF-67 was used as the precursor, and applying heteroatom doping and high temperature heat treatment method 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 characterization 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 show that the prepared FeNi-CoP/NC catalyst has rhombohedral dodecahedron structure and specific surface area is 402 m2/g. The half-wave potential is up to 0.83 V as an electrocatalyst for oxygen reduction reaction in zinc-air batteries. After 5000 cycles, current density only loses 5.06% and half-wave potential hardly changes ,revealing a good stability; the overpotential of OER is 290 mV when current density is 10 mA·cm-2. And the catalyst can be kept stable for 12 h at 100 mA·cm-2. The performance test of the full battery showed that its 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 is 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.