Regulating the Spin State of FeIII by Atomically Anchoring on Ultrathin Titanium Dioxide for Efficient Oxygen Evolution Electrocatalysis

Ferric oxides and (oxy)hydroxides, although plentiful and low-cost, are rarely considered for oxygen evolution reaction (OER) owing to the too high spin state (e_g filling ca. 2.0) suppressing the bonding strength with reaction intermediates. Now, a facile adsorption-oxidation strategy is used to anchor Fe^III atomically on an ultrathin TiO₂ nanobelt to synergistically lower the spin state (e_g filling ca. 1.08) to enhance the adsorption with oxygen-containing intermediates and improve the electro-conductibility for lower ohmic loss. The electronic structure of the catalyst is predicted by DFT calculation and perfectly confirmed by experimental results. The catalyst exhibits superior performance for OER with overpotential 270 mV @10 mA cm^-2 and 376 mV @100 mA cm^-2 in alkaline solution, which is much better than IrO₂ /C and RuO₂ /C and is the best iron-based OER catalyst free of active metals such as Ni, Co, or precious metals.