2018 Volume 71 Pages 18-29
Converting sunlight into storable chemical energy carriers, such as dihydrogen (H2), through light-driven splitting of water is a widely studied approach to secure future energy supplies and sustainability. Molecular complexes based on inexpensive and earthabundant 3d transition metals have been extensively explored as catalysts for the reduction of water to H2. Among these, cobalt complexes with an oxime functionality (i.e., cobaloxime and cobalt diimine-dioxime) efficiently reduce protons in pure water with low to moderate overpotentials, and they have been shown to remain active under aerobic conditions. Based on their simple and straightforward synthesis in addition to their excellent electrochemical properties, they are often applied as the first-choice catalyst when testing new materials or introducing new concepts for H2 evolution. In this review, their basic electrochemical and electrocatalytic properties as well as mechanistic investigations will be summarized, followed by an overview of their application in photocatalysis. Finally, their integration with (nano)materials for (photo)electrocatalytic H2 evolution is presented and discussed.
