In situ constructing Co/Co-Ox/Co-Nx diverse active sites on hollow porous carbon spheres derived from Co-MOF for efficient bifunctional electrocatalysis in rechargeable Zn-air

• Published in: Materials today physics 2023-09, Vol.37, p.101209, Article 101209
• Main Authors: Xue, Song, Qin, Junfeng, Zhang, Xiaohua, Guo, Xi, Hong, Min, Liu, Wuhua, Du, Cuicui, Chen, Jinhua
• Format: Article
• Language: English
• Subjects: Diverse active sites; Metal-organic frameworks; Oxygen evolution reaction; Oxygen reduction reaction; Secondary Zn-Air batteries
• ISSN: 2542-5293; 2542-5293
• DOI: 10.1016/j.mtphys.2023.101209

Earth-rich, durable, and efficient bifunctional electrocatalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is vitally important for the wide application of zinc-air batteries in the future. However, due to the single active site, traditional commercial benchmark catalysts typically exhibit selective activity in only one of the two reactions (ORR or OER), making it difficult to meet the dual functional catalytic requirements. Developing efficient oxygen electrocatalysts that achieve diverse active sites on a single catalyst and understanding their internal synergistic reaction activity remain a challenge. Herein, spherical hollow porous carbon matrix composites (s-Co/CoNC) with the coexistence of diverse intrinsic active sites including Co-Nx and Co-Ox species and metal Co nanoparticles were prepared by pyrolysis with oxygen-enriched Co-MOFs as precursor in the presence of melamine. Owing to the combined advantages of the catalyst including the great specific surface area, good conductivity, abundant diverse intrinsic active sites towards ORR and OER, and the electronic interaction among active sites and the optimized the adsorption/desorption process of oxygen species at the catalyst surface, s-Co/CoNC exhibits desirable electrocatalytic activity for both ORR and OER with an ORR half-wave potential of 0.81 V, an OER potential of 1.53 V(vs. RHE at 10 mA cm−2), providing a small reversible potential difference of 0.72 V, superior to the commercial noble-metal catalysts and the most reported cobalt based ORR/OER catalysts. The assembled s-Co/CoC-based rechargeable Zn-air batteries possess high peak power density of 101.7 mW cm−2. This work provides a significant strategy for constructing high-performance dual functional catalysts for secondary Zn-air batteries. Spherical hollow porous s-Co/CoNC catalyst with diverse active sites of Co-Nx and Co-Ox species and metal Co nanoparticles was successfully prepared by one-step pyrolysis of oxygen-enriched Co-MOFs in the presence of melamine. Based on the spherical hollow porous structural features, the coexistence of the diverse active sites, the regulating N and O coordination environment and the interaction between the diverse active sites, s-Co/CoNC exhibits a desirable bifunctional oxygen electrocatalysis performance with a small potential gap of 0.72 V between Ej = 10 and E1/2, thereby prefiguring a potential promising for engineering applicability in ZABs. [Display omitted] •Spheri