Activating Both Basal Plane and Edge Sites of Layered Cobalt Oxides for Boosted Water Oxidation

Layered A x CoO 2 materials built by stacking layers of CoO 2 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 CoO 2 slabs show too strong adsorption energy to the reaction intermediates, which is unfavorable for the release of O 2 . Here, a simple cation-exchange strategy based on Fe 3+ and alkali ions is proposed to simultaneously activate both the basal plane and edge sites of A x CoO 2 for the OER. X-ray absorption spectroscopy has revealed that the Fe 3+ ions deposit both on the surface and edge sites of the CoO 2 slabs and enter the interlayer. The cation-exchanged A x CoO 2 electrodes show a boosted activity compared to their pristine and conventional Fe-doped A x CoO 2 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 Fe 3+ ions. This work provides a novel method to fully exploit layer-structured materials for efficient energy conversion.