Highly efficient water oxidation via a bimolecular reaction mechanism on rutile structured mixed-metal oxyfluorides
Résumé
Mixed-metal oxides are generally considered to be the highest-performance catalysts for alkaline water oxidation. Despite significant efforts dedicated to understanding and accelerating their efficiency, most works have been limited investigations of Ni, Co, and Fe oxides, thus overlooking the beneficial effects of hetero-anion incorporation. To this end, we report on the development of a Co0.5Fe0.5O0.5F1.5 oxyfluoride catalyst with highly effective catalytic sites for electrochemical water oxidation. In particular, its performance across metrics of Tafel slope (27 mV/dec), mass activity (846 A/g at 1.53 V versus reversible hydrogen electrode [RHE]), turnover frequency (21/s at 1.53 V versus RHE), overpotential (220 mV for 10 mA/cm2), and stability (27 days of continuous operation) largely surpasses those of most known Co-based catalysts. Mechanistic studies suggest that this performance is driven by a bimolecular, oxygen-coupling reaction mechanism through proximal active sites on the catalyst surface, thus enabling a new avenue for achieving accelerated oxygenic electrocatalysis.
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