Schiff Base Complex Cocatalyst with Coordinatively Unsaturated Cobalt Sites for Photoelectrochemical Water Oxidation.

Integrating inorganic oxygen evolution cocatalysts (OECs) with photoanodes is regarded as an available strategy to increase the photogenerated charge utilization for accelerated water oxidation kinetics. Nevertheless, most widely used transition metal (oxyhydr)oxides OECs suffer from inevitable charge recombination at photoanode/OECs interfaces and underabundant catalytic active sites. Herein, a cobalt-organic complex with microflower-like features (denoted as MF) was constructed by coordination of Schiff base ligands and Co 2+ metal ions and then decorated on porous BiVO 4 employed as photoanodes for photoelectrochemical (PEC) water oxidation. The as-synthesized BiVO 4 /MF photoanode achieves a photocurrent density of 4.38 mA cm -2 and at 1.23 V RHE in 0.5 M Na 2 SO 4 electrolyte under simulated 1 sun illumination, over approximately 5.48 times larger than that of BiVO 4 counterpart, and exhibits a 120 mV cathodic shift of onset potential with outstanding photostability. Systematic characterizations reveal that the improved PEC efficiency is mainly attributed to the well-designed coordinatively unsaturated Co 2+ sites, which not only serve as powerful photohole extraction engines along reversed interfacial Co-O-Bi bonds to promote charge transfer across the BiVO 4 /complex interface but also act as reaction active centers by accelerating surface water oxidation kinetics. This work provides new insights for designing highly effective OECs for PEC water oxidation.