N-doped ZrO2 nanoparticles embedded in a N-doped carbon matrix as a highly active and durable electrocatalyst for oxygen reduction

• Published in: Fundamental research (Beijing) Vol. 2; no. 4; pp. 604 - 610
• Main Authors: Cao, Xuejie, Zheng, Siyu, Wang, Tongzhou, Lin, Fei, Li, Jinhong, Jiao, Lifang
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.07.2022; KeAi Publishing; KeAi Communications Co. Ltd
• Subjects: Band-gap structure; Nitrogen doping; Oxygen reduction reaction; Zirconium dioxide; Zn-air batteries; Band-gap structure; Nitrogen doping; Zirconium dioxide; Oxygen reduction reaction; Zn-air batteries
• ISSN: 2667-3258; 2096-9457; 2667-3258
• DOI: 10.1016/j.fmre.2021.08.014

Fabricating highly efficient and robust oxygen reduction reaction (ORR) electrocatalysts is challenging but desirable for practical Zn-air batteries. As an early transition-metal oxide, zirconium dioxide (ZrO2) has emerged as an interesting catalyst owing to its unique characteristics of high stability, anti-toxicity, good catalytic activity, and small oxygen adsorption enthalpies. However, its intrinsically poor electrical conductivity makes it difficult to serve as an ORR electrocatalyst. Herein, we report ultrafine N-doped ZrO2 nanoparticles embedded in an N-doped porous carbon matrix as an ORR electrocatalyst (N-ZrO2/NC). The N-ZrO2/NC catalyst displays excellent activity and long-term durability with a half-wave potential (E1/2) of 0.84 V and a selectivity for the four-electron reduction of oxygen in 0.1 M KOH. Upon employment in a Zn-air battery, N-ZrO2/NC presented an intriguing power density of 185.9 mW cm−2 and a high specific capacity of 797.9 mA h gZn−1, exceeding those of commercial Pt/C (122.1 mW cm−2 and 782.5 mA h gZn−1). This excellent performance is mainly attributed to the ultrafine ZrO2 nanoparticles, the conductive carbon substrate, and the modified electronic band structure of ZrO2 after N-doping. Density functional theory calculations demonstrated that N-doping can reduce the band-gap of ZrO2 from 3.96 eV to 3.33 eV through the hybridization of the p state of the N atom with the 2p state of the oxygen atom; this provides enhanced electrical conductivity and results in faster electron-transfer kinetics. This work provides a new approach for the design of other enhanced semiconductor and insulator materials.