The simple construction of rice-husk-derived carbon catalyst for oxygen reduction reaction by the synergism of iron and nitrogen co-doping

Abstract

Electrocatalysts with high efficiency and low cost are urgently being developed for commercial application in modern energy conversion systems. Herein, biochar-based electrocatalytic materials (RHFeN) with oxygen reduction catalytic activity are obtained by using rice husk as carbon precursor, doping with Fe metal salt, and high-temperature ammonia etching and doping. The experimental results show that the catalyst material presents an amorphous carbon structure, in which a large number of nanometal composite particles are uniformly embedded. The particles are coated by a thin layer of amorphous carbon, and the outer edge shows a zigzag defect structure. The pyrolysis temperature for rice husk carbon, the element doping, the addition of metal Fe salt and the etching temperature of ammonia had significant effects on the catalytic performance of the materials. Fe and N co-doping can significantly improve the electrocatalytic performance of materials for ORR. When the pyrolysis temperature of rice husk was 400 °C, the added metal Fe salt was 2.0 mL (6.99 mg Fe per mL), and the etching temperature of ammonia was 800 °C, RHFeN catalyst with the best oxygen reduction catalytic performance was obtained. In addition, the zinc–air battery derived using the RHFeN catalyst shows a 1.4 V open-circuit voltage and high peak power density (156.1 mW cm⁻²). As a low-cost, renewable, biomass-based electrocatalytic material, Fe and N co-doped rice husk carbon would have great research and application value in the field of energy conversion and storage due to its excellent ORR activity and simple, large-scale preparation method.