Elucidating the reaction pathway of crystalline multi-metal borides for highly efficient oxygen-evolving electrocatalysts

• Published in: Journal of materials chemistry. A, Materials for energy and sustainability Materials for energy and sustainability, 2022-01, Vol.1 (3), p.1569-1578
• Main Authors: Zhao, Shijing, Xu, Shishuai, Yao, Jinlei, Chen, Ning, Gong, Yutong, Zhang, Xipeng, Hao, Xianfeng, Zhang, Lijuan, Pei, Cuiying, Tian, Ruifeng, Wu, Lailei, Wan, Biao, Peng, Wenfeng, Gao, Bo, Qi, Yanpeng, Gao, Faming, Ahuja, Rajeev, Yao, Yansun, Gou, Huiyang
• Format: Article
• Language: English
• Subjects: Borides; Boron; Catalysts; Cobalt; Crystal structure; Crystallinity; Durability; Electrocatalysts; Electronic structure; Hydrogen evolution reactions; Iron; Metals; Molybdenum; Oxygen; Oxygen evolution reactions; Renewable energy; Selectivity
• ISSN: 2050-7488; 2050-7496; 2050-7496
• DOI: 10.1039/d1ta09078j

Understanding the fundamental principle of catalytic performance and the mechanism of multimetal-based electrocatalysts is essential for the rational design of advanced renewable energy systems. Here, highly crystalline MMMoB 4 (M = Fe, Co) compounds with controllable compositions of multiple active metal atoms and polyacene-type boron networks were synthesized delicately by a one-step high-pressure technique to explore electrocatalytic selectivity and activity. CoFeMoB 4 and Co 2 MoB 4 are revealed to be highly active and durable oxygen evolution reaction (OER) electrocatalysts under alkaline conditions. The mutually promotive activation of metals with amorphous clusters and ultra-small grains on the surface are responsible for the enhanced activity of CoFeMoB 4 . More specifically, Co and Fe coupling in CoFeMoB 4 facilitates surface reconstruction into active Co hydroxide and Fe oxyhydroxide, in contrast to Co oxyhydroxide in Co 2 MoB 4 and Fe oxides in Fe 2 MoB 4 . Dissolving Mo may provide potential space for adsorbing hydroxyl, and the optimized electronic structure with boron is mainly responsible for the long-term durability. In contrast, Mo atoms are responsible for hydrogen evolution reaction (HER) properties, and the optimized d-band center and density of states at the Fermi level make Co 2 MoB 4 a superior HER catalyst. Our findings provide insight into distinguishing the catalytic pathway of multi-metal borides with improved OER activity and different roles of Mo and Co/Fe in the HER and OER. Highly crystalline CoFeMoB 4 synthesized by high-pressure and high-temperature method boosts the OER performance by synergistic effect of Co 2+ and Fe 3+ ions from the amorphous clusters and ultra-small grains at the surface layer.