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

Abstract

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 electro- and photocatalytic reduction of water to H2. As an electrocatalyst, [(btep)CoBr2] can provide 591.9 mol of hydrogen per mole of catalyst per hour (mol H2/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 (H2A) (0.12 M) as a sacrificial electron donor in an aqueous solution (pH 4.5), [(btep)CoBr2] can afford 9326.4 mol H2 per mole of catalyst over a 40 h irradiation with blue light (λmax = 469 nm). The highest apparent quantum yield (AQY) is ~ 25.5%. The catalytic mechanism for H2 production was investigated by several measurements and analysis.