An Efficient Strategy for Boosting Photogenerated Charge Separation by Using Porphyrins as Interfacial Charge Mediators

Surface recombination at the photoanode/electrolyte junction seriously impedes photoelectrochemical (PEC) performance. Through coating of photoanodes with oxygen evolution catalysts, the photocurrent can be enhanced; however, current systems for water splitting still suffer from high recombination. We describe herein a novel charge transfer system designed with BiVO4 as a prototype. In this system, porphyrins act as an interfacial-charge-transfer mediator, like a volleyball setter, to efficiently suppress surface recombination through higher hole-transfer kinetics rather than as a traditional photosensitizer. Furthermore, we found that the introduction of a "setter" can ensure a long lifetime of charge carriers at the photoanode/electrolyte interface. This simple interface charge-modulation system exhibits increased photocurrent density from 0.68 to 4.75 mA cm-2 and provides a promising design strategy for efficient photogenerated charge separation to improve PEC performance.