The production of hydrogen through water splitting using earth-abundant metal catalysts is a promising pathway for converting solar energy into chemical fuels. However, existing approaches for fine stoichiometric control, structural and catalytic modification of materials by appropriate choice of earth abundant elements are either limited or challenging. Here we explore the tuning of redox active immobilised molecular metal-chalcoxide electrocatalysts by controlling the chalcogen or metal stoichiometry and explore critical aspects of the hydrogen evolution reaction (HER). Linear sweep voltammetry (LSV) shows that stoichiometric and structural control leads to the evolution of hydrogen at low overpotential with no catalyst degradation over 1000 cycles. Density functional calculations reveal the effect of the electronic and structural features and confer plausibility to the existence of a unimolecular mechanism in the HER process based on the tested hypotheses. We anticipate these findings to be a starting point for further exploration of molecular catalytic systems.

The electrocatalytic hydrogen evolution reaction (HER) is of central importance for the production of H2 from sustainable sources. Currently, Pt is the best electrocatalyst for this transformation, but other materials based on less‐precious elements are now attracting increased attention. Of these alternatives, the molybdenum chalcogenides show particular promise. MoS2 has been explored extensively in this regard, which has highlighted the important role of polymorphism for catalytic activity. However, the conversion into an active polymorph is complex, and the stability of the catalyst under electrochemical conditions is poor. In contrast, MoTe2 has been barely studied as an electrocatalyst for the HER. Herein, we isolate the semiconducting and metallic polymorphs of MoTe2 using an easy solid‐state route and show that interconversion between the two polymorphs of MoTe2 can be achieved without a change in morphology by a simple temperature‐annealing protocol. Although the semiconducting form is a rather poor electrocatalyst for the HER, the metallic 1T′‐MoTe2 polymorph is an efficient and stable electrocatalyst for the HER in 1 m H2SO4. Even in the bulk form, it achieved a low overpotential with a Tafel slope of (78±4) mV dec−1 and full Faradaic efficiency. These findings highlight the importance of polymorphic control in the development of HER catalysts and suggest an efficient route for the discovery of new and improved electrocatalysts.

The chiral dicobalt(II) complex [CoII2(μ2-L)2] (1) (H2L = N2,N6-di(quinolin-8-yl)pyridine-2,6-dicarboxamide) and its tert-butyl analogue [CoII2(μ2-LBu)2] (2) were synthesized and structurally characterized. Addition of one equivalent of AgSbF6 to the dichloromethane solution...

Coordinating rare earth ions to bis(dithiooxalato)nickel produces the first structurally characterised complexes possessing the elusive dithiooxalato radical ligand.

Molecular metal chalcogenides have attracted great attention as electrocatalysts for the hydrogen evolution reaction (HER). However, efficient utilisation of the active sites and catalytic performance modulation has been challenging. Here...