A cobalt complex of bis(methylthioether)pyridine, a new catalyst for hydrogen evolution

A new cobalt complex, [(btep)CoBr2], was produced by the reaction of CoBr2 and bis(methylthioether) pyridine (btep), and its structure has been determined by X-ray crystallography. [(btep)CoBr2] shows good activity for the electroand photocatalytic reduction of water to H-2. As an electrocatalyst, [(btep) CoBr2] can provide 591.9 mol of hydrogen per mole of catalyst per hour (mol H-2/mol catalyst/h) from neutral water under an overpotential (OP) of 837.6 mV. As a co-catalyst in a photocatalytic system, together with CdS nanorods (CdS NRs) (0.14 mg mL(-1)) as a photosensitizer, and ascorbic acid (H(2)A) (0.12 M) as a sacrificial electron donor in an aqueous solution (pH 4.5), [(btep)CoBr2] can afford 9326.4 mol H-2 per mole of catalyst over a 40 h irradiation with blue light (lambda(max) = 469 nm). The highest apparent quantum yield (AQY) is similar to 25.5%. The catalytic mechanism for H-2 production was investigated by several measurements and analysis. (c) 2020 Elsevier Ltd. All rights reserved.