Rapid Thermal Annealing toward High-Quality 2D Cobalt Fluoride Oxide as an Advanced Oxygen Evolution Electrocatalyst

Tailoring the composition and morphology of electrocatalysts has been regarded as an effective alternative to improve their catalytic performance by forming and exposing more active sites. Herein a rapid thermal annealing (RTA) strategy is proposed to mass produce 2D cobalt-fluoride-oxide phase electrocatalysts in air at 400 °C (CFO-RH400) from crystalline fluoride hydrates, with critical steps including the thermal expansion of the water molecule, the exfoliation of CoF2 nanosheets, and the subsequent oxidation. The regulated electronic structure of the active cobalt oxide phase by sufficient fluoride anions leads to a closer O p-band center relative to the Fermi level based on our theoretical simulations. Therefore, the as-prepared 2D CFO-RH400 exhibits superior electrocatalytic activity and durability toward the oxygen evolution reaction.