2LaCo0.7Fe0.3O3/N-doped carbon bifunctional electrocatalyst derived from g-C3N4 nanosheets for zinc-air battery

• Published in: Electrochimica acta 2022-05, Vol.414, p.140211, Article 140211
• Main Authors: Liu, Haoquan, Ren, Xinghui, Bai, Haoyang, Qiao, Huici, Lu, Jinwei, Wang, Xuefei, Huang, Hao, Hu, Jie
• Format: Article
• Language: English
• Subjects: Carbon; Carbon nitride; Chemical reduction; Composite materials; Crystal structure; Density functional theory; DFT calculation; Electrocatalyst; Electrocatalysts; Electronic structure; Free energy; Metal air batteries; N-doped carbon; Nanoparticles; Nanosheets; Nitrogen; Oxygen evolution reactions; Oxygen reduction reactions; Perovskite; Perovskites; Sol-gel processes; Substrates; Zinc-oxygen batteries; Zn-air battery
• ISSN: 0013-4686; 1873-3859
• DOI: 10.1016/j.electacta.2022.140211

•LCFO/xNC hybrids are prepared using CNNS as carbon and nitrogen source.•The high dispersion of perovskite on the NC substrate exposes more active sites.•2LCFO/NC has high concentration of oxygen vacancies to promote the adsorption.•The enhancement Co-O covalency is beneficial to the electrocatalytic process.•The reduction of RDS free energy change accelerate the reaction process. Perovskite oxides have been widely studied as one of the excellent bifunctional oxygen electrocatalysts (ORR: Oxygen Reduction Reaction, OER: Oxygen Evolution Reaction) due to its flexible crystal structure and low cost. Herein, 2LaCo0.7Fe0.3O3/N-doped carbon is prepared by sol-gel method using g-C3N4 nanosheets as carbon source and nitrogen source. The LaCo0.7Fe0.3O3 nanoparticles have excellent dispersibility on the N-doped carbon substrate and the composite material has higher oxygen vacancy concentration, showing enhanced bifunctional electrocatalytic activity (△E=Ej=10,OER-E1/2,ORR=1.03 V) compared with the original LaCo0.7Fe0.3O3 (△E = 1.12 V). Moreover, 2LaCo0.7Fe0.3O3/N-doped carbon-based Zn-air battery presents excellent cycling stability (over 24 h) and high peak power density of 116 mW cm−2. Density functional theory (DFT) calculations revealed the mechanism of improvement electrocatalytic activity of 2LaCo0.7Fe0.3O3/N-doped carbon, which comes from the regulated electronic structure, including enhanced conductivity and the covalence of Co-O bond, reducing the free energy change of rate-determining step. This study provides a novel strategy for the design and prepare perovskite-type bifunctional electrocatalysts. Multi-factor optimization in 2LaCo0.7Fe0.3O3/N-doped carbon, including high oxygen vacancy concentration, improved conductivity and the covalence Co-O bond, and reducing the free energy change of rate-determining step. [Display omitted]