Development and understanding of cobaloxime activity through electrochemical molecular catalyst screening

Abstract

Electrochemical molecular catalyst screening (EMoCS) has been developed. This technique allows fast analysis and identification of homogeneous catalytic species through tandem catalyst assembly and electrochemistry. EMoCS has been used to study molecular proton reduction catalysts made from earth abundant materials to improve their viability for water splitting systems. The efficacy of EMoCS is proven through investigation of cobaloxime proton reduction activity with respect to the axial ligand in aqueous solution. Over 20 axial ligands were analysed, allowing rapid identification of the most active catalysts. Structure–activity relationships showed that more electron donating pyridine ligands result in enhanced catalytic currents due to the formation of a more basic Co–H species. The EMoCS results were validated by isolating and assaying the most electroactive cobaloximes identified during screening. The most active catalyst, [Co^IIICl(dimethyl glyoximato)₂(4-methoxypyridine)], showed high electro- and photoactivity in both anaerobic and aerobic conditions in pH neutral aqueous solution.