Molecular Ru(<scp>ii</scp>) complexes with universal pH hydrogen evolution performance

The development of efficient and robust hydrogen evolution reaction (HER) catalysts that operate across a wide pH range is critical for advancing sustainable hydrogen production. Previously, a series of molecular complexes have been immobilized on solid supports to achieve efficient HER activity. However, achieving HER activity with molecular complexes across a universal pH range still remains challenging. Herein, we demonstrated two Ru(II) complexes and systematically characterized them using spectroscopic techniques. The (MeTBEN)Ru(II) complex (2) exhibited outstanding hydrogen evolution activity across a wide pH range, specifically in alkaline, neutral, and acidic electrolytes, with the highest performance observed in acidic electrolytes compared to the (BnTBEN)Ru(II) complex (1). 2 demonstrates outstanding electrocatalytic performance with a low overpotential of 115 mV at 10 mA cm^-2 in 0.5 M H₂SO₄, along with an excellent turnover frequency. Furthermore, 2 demonstrated excellent electrochemical stability, sustaining its activity for up to 8 hours under acidic conditions.