Water Oxidation Catalyzed By Novel Copper And Cobalt Complexes

Conversion of solar energy into clean, renewable hydrogen has been a potential way to solve energy crisis. Among overall water splitting, water oxidation is a considered a major bottleneck due to its four protons and four electrons process and the uphill thermodynamics. The molecular water oxidation catalysts mainly based on precious metals such as Ru and Ir have been widely investigated. However, catalysts made by earth abundant metals such as Fe, Co, Mn, Cu are relatively limited. Therefore, development of non-noble catalysts capable of oxidizing water to dioxygen and incorporation into photoelectrochemical (PEC) cells is highly desired.In this study, eight Cu complexes were designed and synthesized, three of which were found to be able to catalyze electrochemical water oxidation under strong basic conditions. The highest catalytic current is up to520μA/cm2with an overpotential of1.6V. vs NHE. These results are comparable to previously reports, which expands the range of water oxidation catalysts based on earth-abundant metal complexes, and are of importance for rational design of highly efficient water oxidation catalysts in future.Moreover, water oxidation catalyst based on coblat cubane complex, for the first time, was integrated with photosensitizer to form a supromelecular assembly by host-guest interaction. The assembly was found to be more efficient with respect to traditional three components system in light-driven oxygen evolution. Though no activity was detected in PEC cell by immobilization of the assembly on TiO2as a composite photoanode, the photoanode showed high photocurrent under a bias of0.2V vs NHE by replacing cobalt cubane with a ruthenium catalyst.