A homogeneous cobalt complex mediated electro and photocatalytic O2/H2O interconversion in neutral water

The O-2/H2O redox couple is vital in various renewable energy conversion strategies. This work delves into the Co(L-histidine)(2) complex, a functional mimic of oxygen-carrying metalloproteins, and its electrochemical behavior driving the bidirectional oxygen reduction (ORR) and oxygen evolution (OER) activity in neutral water. This complex electrocatalyzes O-2 via two distinct pathways: a two-electron O-2/H2O2 reduction (catalytic rate = 250 s(-1)) and a four-electron O-2 to H2O production (catalytic rate = 66 s(-1)). The formation of the key trans-m-1,2-Co(III)-peroxo intermediate expedites this process. Additionally, this complex effectively oxidizes water to O-2 (catalytic rate = 15606 s(-1)) at anodic potentials via a Co(IV)-oxo species. Additionally, this complex executes the ORR and OER under photocatalytic conditions in neutral water in the presence of appropriate photosensitizer (Eosin-Y) and redox mediators (triethanolamine/ORR and Na2S2O8/OER) at an appreciable rate. These results highlight one of the early examples of both electroand photoactive bidirectional ORR/OER catalysts operational in neutral water.

Automated summary

This study investigates the importance of the O-2/H2O redox couple in renewable energy conversion and introduces a functional mimic compound that exhibits catalytic activity for bidirectional oxygen reduction and oxygen evolution. The compound shows high catalytic activity in neutral water and can perform both oxygen reduction and oxygen evolution under photocatalytic conditions.