Oxygen evolution reaction over catalytic single-site Co in a well-defined brookite TiO₂ nanorod surface

Efficient electrocatalysts for the oxygen evolution reaction (OER) are paramount to the development of electrochemical devices for clean energy and fuel conversion. However, the structural complexity of heterogeneous electrocatalysts makes it a great challenge to elucidate the surface catalytic sites and OER mechanisms. Here, we report that catalytic single-site Co in a well-defined brookite TiO₂ nanorod (210) surface (Co-TiO₂) presents turnover frequencies that are among the highest for Co-based heterogeneous catalysts reported to date, reaching 6.6 ± 1.2 and 181.4 ± 28 s⁻¹ at 300 and 400 mV overpotentials, respectively. Based on grand canonical quantum mechanics calculations and the single-site Co atomic structure validated by in situ and ex situ spectroscopic probes, we have established a full description of the catalytic reaction kinetics for Co-TiO₂ as a function of applied potential, revealing an adsorbate evolution mechanism for the OER. The computationally predicted Tafel slope and turnover frequencies exhibit exceedingly good agreement with experiment. [Figure not available: see fulltext.]