Effects of halogen ligands of complexes supported by bis(methylthioether)pyridine on catalytic activities for electrochemical and photochemical driven hydrogen evolution

Reactions of bis(methylthioether)pyridine (btep) with CuX 2 (X = Br and Cl) form two new complexes, [Cu(btep)Br 2 ] and [Cu(btep)Cl 2 ], respectively, which have been determined by X‐ray crystallography. Both of them can serve as catalysts for electrochemical and photochemical driven hydrogen evolution. Under an overpotential (OP) of 837.6 mV, [Cu(btep)Br 2 ] or [Cu(btep)Cl 2 ] can electrocatalyze hydrogen evolution from a neutral water with a turnover frequency (TOF) of 373 and 120 mol of hydrogen per mole of catalyst per hour (mol H 2 /mol catalyst/h), respectively. Under blue light, mixing with CdS nanorods (CdS NRs) as a photosensitizer, and ascorbic acid (H 2 A) as a sacrificial electron donor, the photolysis of an aqueous solution (pH 4.5) with [Cu(btep)Br 2 ] or [Cu(btep)Cl 2 ] can provide 6180 and 5120 mol of H 2 per mole of catalyst (mol of H 2 (mol of cat) −1 ) during 48‐h irradiation with an average apparent quantum yield of 16.7% and 11.0%, respectively. The results show that [Cu(btep)Br 2 ] shows a more efficient activity for H 2 generation than [Cu(btep)Cl 2 ]. Several electrochemical and photochemical measurements and analysis are carried out to study catalytic mechanism for H 2 production.