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Cobalt compounds; Conversion efficiency; Positive ions; Reaction intermediates; X ray absorption spectroscopy, Adsorption energies; Cation exchanges; Charge redistribution; Layer structured materials; Layered cobalt oxides; Oxygen evolution reaction (oer); Stacking layers; Water oxidation, Iron metallography
Abstract:
Layered AxCoO2 materials built by stacking layers of CoO2 slabs and inserting alkali ions in between them have shown a promising activity of oxygen evolution reaction (OER) due to their active edge sites. However, the large basal plane areas of the CoO2 slabs show too strong adsorption energy to the reaction intermediates, which is unfavorable for the release of O2. Here, a simple cation-exchange strategy based on Fe3+ and alkali ions is proposed to simultaneously activate both the basal plane and edge sites of AxCoO2 for the OER. X-ray absorption spectroscopy has revealed that the Fe3+ ions deposit both on the surface and edge sites of the CoO2 slabs and enter the interlayer. The cation-exchanged AxCoO2 electrodes show a boosted activity compared to their pristine and conventional Fe-doped AxCoO2 counterparts. This phenomenon is mainly ascribed to the abundant edge-sharing Co–Fe motifs at the edge sites and the charge redistribution in the basal plane sites induced by the insertion of Fe3+ ions. This work provides a novel method to fully exploit layer-structured materials for efficient energy conversion. © 2021 Wiley-VCH GmbH.
