Photo- and electrocatalytic H2 evolution with cobalt oxime complexes

41 in of electro-and photocatalytic integrate materials devices for (light-driven) H 2 evolution. 42–47 the application cobalt oxime complexes as catalysts in such systems reviewed. Converting sunlight into storable chemical energy carriers, such as dihydrogen (H 2 ), through light-driven splitting of water is a widely studied approach to secure future energy supplies and sustainability. Molecular complexes based on inexpensive and earth-abundant 3d transition metals have been extensively explored as catalysts for the reduction of water to H 2 . 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 H 2 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 H 2 evolution is presented and discussed.