In situ revealing the reconstruction behavior of monolayer rocksalt CoO nanosheet as water oxidation catalyst

• Published in: Journal of energy chemistry 2022-07, Vol.70, p.373-381
• Main Authors: Guo, Weiqi, Luo, Haolin, Fang, Dongxu, Jiang, Zhi, Chi, Jiasheng, Shangguan, Wenfeng
• Format: Article
• Language: English
• Subjects: In situ experiments; Oxygen evolution reaction; Rocksalt CoO; Two-dimension materials; X-ray absorption spectroscopy
• ISSN: 2095-4956
• DOI: 10.1016/j.jechem.2022.02.049

Utilizing two-dimensional material as a model catalyst, the reconstruction behavior of rocksalt CoO during oxygen evolution reaction was revealed by in situ X-ray absorption spectroscopy. [Display omitted] The reconstruction during oxygen evolution reaction (OER) significantly affects the electronic and local geometry structure of metal sites in electrocatalyst. Compared with well-investigated cobalt-based materials, the reconstruction of rocksalt CoO with purely Co2+ in octahedral (Oh) coordination has not been revealed in detail. Herein, monolayer CoO supported on reduced graphene oxide (rGO) was synthesized via a one-pot hydrothermal strategy with calcinating in Ar atmosphere. The structure evolution of two-dimension (2D) CoO/rGO during OER was revealed by in situ X-ray absorption spectroscopy (XAS). The transition from CoO toward Co3O4 already occurred at open circuit potential, further enhanced at 1.23 V (vs. RHE). The CoOx(OH)y was determined as the active phase at 1.53 V, displaying a tetrahedral Co coordination defective spinel Co3O4 with the Co-O shell that featured the (oxy)hydroxide, not the standard CoOOH. After OER, the irreversible transition from CoO to Co3O4 was observed. In contrast, in situ Raman spectra revealed a reversible amorphization process on Co3O4/rGO under operation conditions. Furthermore, this study indicated that the reconstruction behavior could be more effectively revealed by XAS using 2D materials.