S,S′‐bis(2‐pyridylmethyl)‐1,2‐thioethane (bpte) reacts with MCl2 (M = Co, Ni, and Fe) to give three complexes, namely, [CoII(bpte)Cl2] (1), [NiII(bpte)Cl2] (2), and [FeII(bpte)Cl2] (3), respectively. They all act as catalysts for proton or water reduction to dihydrogen via electrolysis or photolysis. Under an overpotential of 837.6 mV, the electrolysis of a neutral buffer with complex 1, 2, or 3 can provide 418 (±3), 555 (±3), and 243 (±3) moles of hydrogen per mole of catalyst per hour (mol H2/mol catalyst/h), respectively. Under blue light, together with a photosensitizer and ascorbic acid (H2A) as a sacrificial electron donor, the photolysis of an aqueous solution (pH 4.5) containing complex 1, 2, or 3 can afford 9060 (±5), 24,900 (±5), and 10,630 (±5) moles H2 per mole of catalyst (mol of H2 [mol of cat]−1) during 83‐h irradiation with an average apparent quantum yield of 7.1%, 24%, and 10%, respectively. The results show that the nickel complex [NiII(bpte)Cl2] exhibits a more efficient activity for hydrogen generation than the iron or cobalt species. These findings may offer a new chemical paradigm for the design of efficient catalysts.

Based on that hydrogen energy is widely used in fuel cells, the design and research of new catalysts for both hydrogen evolution reactions (HERs) and hydrogen oxidation reactions (HORs) are becoming increasingly important. A new catalyst for both hydrogen evolution and oxidation, based on a zinc complex, [Zn‐ATSE]2, is designed and provided by the reaction of Zn (CH3CO2)2 with diacetyl‐2‐(4‐N‐ethyl‐3‐thiosemicarbazone)‐3‐(4‐N‐amino‐3‐thiosemicarbazone) (H2ATSE) in our group. Electrochemical investigations show that [Zn‐ATSE]2 can electro‐catalyze hydrogen evolution from acetic acid with a turnover frequency (TOF) of 64 mol H2 mol catalyst−1 h−1 under an overpotential of 914.6 mV. Moreover, [Zn‐ATSE]2 also can electro‐catalyze hydrogen oxidation with a TOF of 13.52 s−1. The results can be attributed to the hydrazine group of [Zn‐ATSE]2 that can form a ligand‐based radical species. Possible electrocatalytic cycles for H2 production and oxidation by [Zn‐ATSE]2 are afforded. We hope these findings can afford a new method for the design of electrocatalysts for both H2 evolution and H2 oxidation.

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. K E Y W O R D S copper complexes, crystal structures, electrocatalyst and photocatalyst, proton and water reduction to dihydrogen