Edge/Defect Sites in α-Co_1-m Fe_m (OH)_x Nanoplates Responsible for Water Oxidation Activity

Fe-doped transition metal (oxy)hydroxides are regarded as the most efficient oxygen evolution reaction (OER) electrocatalysts in alkaline conditions. The incorporation of Fe effectively enhances the OER activity of Co-/Ni-based materials, but the corresponding role of Fe in Co-based (oxy)hydroxide materials still remains unresolved. Herein, α-Co_1-m Fe_m (OH)_x is synthesized and systematically engineered to study the effect of Fe content on the morphology, crystalline structure, electronic structure, and OER activity. As the Fe content is changed, the basic crystalline phase of α-Co_1-m Fe_m (OH)_x is consistent whereas the micromorphology changes. Much smaller and thinner nanoplates with more edge/defect sites are fabricated because of increased Fe incorporation. When the Fe content is more than 0.1, twin nanoparticles emerge at the edge/defect sites of the sister nanoplate. Additionally, the OER activity of α-Co_1-m Fe_m (OH)_x against Fe content can be plotted as a volcano curve. These data thus support a hypothesis that the edge/defect sites in α-Co_1-m Fe_m (OH)_x are responsible for the OER performance. The incorporation of Fe leads to not only the accelerated intrinsic reactivity of each active site, which is attributed to the strong electronic interaction between Co and Fe but also changes the number of edge/defect sites.