Mono-nuclear ruthenium catalyst for hydrogen evolution

Molecular hydrogen (H2) is one of the future energy carriers when replacing fossil sources. Enzymatic systems serve as an inspiration for the design of novel hydrogen evolving catalysts. Though several heterobimetallic Ru systems are known as catalysts for the hydrogen evolution reaction (HER), homogeneous mononuclear Ru systems have not been explored much. Here, a new mononuclear Ru(II) complex [cis-RuCl2(PPh3)2(κ2-TL)] (TL = 2-thiophenyl benzimidazole) possessing distorted octahedral geometry, has been synthesised and characterized as an efficient catalyst for acid-assisted hydrogen evolution by using various spectroscopic techniques as well as quantum chemical calculations. When trifluoroacetic acid is used as the proton source, the complex shows remarkable catalytic activity towards H2 production. Based on the DFT calculations, an EECC mechanism could be proposed for HER, consistent with the assignment of the observed redox transitions.