Mechanism-directed design and synthesis of a dinuclear copper porphyrin for efficient electrocatalytic hydrogen evolution reaction

• Present mechanism-directed design and synthesis of a dinuclear Cu porphyrin for catalytic hydrogen evolution reaction. • Reveal the critical role of intramolecular electron transfer between the two Cu atoms in improving the catalysis of hydrogen evolution. • Provide a research paradigm to investigate intramolecular electron transfer involved in catalytic hydrogen evolution. Developing efficient catalysts for the hydrogen evolution reaction (HER) is vital for a H 2 -based energy system. Designing catalysts based on the HER mechanisms is required but has been rarely achieved. Herein, we report on a dinuclear Cu porphyrin for HER. We recently identified an intermolecular electron transfer mechanism in the HER with Cu porphyrins. We consider realizing intramolecular electron transfer between Cu porphyrins to improve HER. By linking two porphyrin units through an alkynyl group, we synthesized dinuclear Cu porphyrin 1 with two conjugated porphyrin units. Electrochemical studies confirm the effective interaction between the two Cu porphyrin units. Importantly, for HER electrocatalysis, the i cat / i p value with 1 (204) is seven times larger than that with its mononuclear analogue (29). Experimental and theoretical studies confirm intramolecular electron transfer in the HER with 1 . This work is therefore significant in presenting a mechanism-directed design of 1 as a highly active HER catalyst.