Tuning Co²⁺ Coordination in Cobalt Layered Double Hydroxide Nanosheets via Fe³⁺ Doping for Efficient Oxygen Evolution

Inexpensive and efficient electrocatalysts are crucial for the development and practical application of energy conversion and storage technologies. Layered-double-hydroxide (LDH) materials have attracted much attention due to the special layered structure, but their electrocatalytic activity and stability are still limited. Herein, we propose to tune Co²⁺ occupancy and coordination in cobalt-based LDH nanosheets via Fe³⁺ doping for efficient and stable electrocatalysis for oxygen evolution reaction (OER). It is found that Fe doping regulates the occupancy and coordination of Co²⁺ in CoO₄ tetrahedrons and CoO₆ octahedrons of Co-LDHs. Through density functional theory calculation, we also clarified that Fe³⁺ not only modulated the Co²⁺ coordination but also functioned as an added catalytic active site. LDH nanosheets with a Co/Fe ratio of 5:1 show a low OER overpotential, much better than the commercial IrO₂, owing to the modulation of Fe³⁺ doping on the crystal and electronic structures. After appropriate incorporation of Fe³⁺, the almost inactive octahedral coordinated Co²⁺ is significantly activated with a partial deletion of tetrahedral coordinated Co²⁺, which greatly boosts the overall electrocatalytic activity. This study offers some new insights into tuning the crystal and electronic structures of LDHs by lattice doping to achieve high-efficiency electrocatalysis for OER.