An Active-Site Sulfonate Group Creates a Fast Water Oxidation Electrocatalyst That Exhibits High Activity in Acid

The storage of solar energy in chemical bonds will depend on pH-universal catalysts that are not only impervious to acid, but actually thrive in it. Whereas other homogeneous water oxidation catalysts are less active in acid, we report a catalyst that maintained high electrocatalytic turnover frequency at pH values as low as 1.1 and 0.43 (k(cat)=1501 +/- 608 s(-1) and 831 +/- 254 s(-1), respectively). Moreover, current densities, related to catalytic reaction rates, ranged from 15 to 50 mA cm(-2) mM(-1) comparable to those reported for state-of-the-art heterogeneous catalysts and 30 to 100 times greater than those measured for two prominent literature homogeneous catalysts at pH 1.1 and 0.43. The catalyst also exhibited excellent durability when a chemical oxidant was used (Ce-IV, 7400 turnovers, TOF 0.88 s(-1)). Preliminary computational studies suggest that the unusual active-site sulfonate group acts a proton relay even in strong acid, as intended.

Automated summary

This study reports a catalyst that maintains high electrocatalytic turnover frequency at very low pH values, with high current densities and excellent durability. Preliminary computational studies suggest that the sulfonate group in the active site acts as a proton relay even in strong acid.