A Thiosemicarbazone-Nickel(II) Complex as Efficient Electrocatalyst for Hydrogen Evolution

We report herein the synthesis and characterization of a new mononuclear nickel complex based on a thiosemicarbazone ligand that exhibits an electrocatalytic behavior for H-2 evolution in DMF using trifluoroacetic acid (TFA) as the proton source. Catalysis is observed at quite small overpotential values and a maximum turnover frequency (TOFmax) of 3080 s(-1) was extrapolated for 1M proton concentration using the foot-of-the wave analysis of cyclic voltammetry data. Gas analysis during controlled potential electrolysis experiments confirmed the catalytic nature of the process and production of dihydrogen with 80% faradaic yield. Quantum chemical calculations indicate that the catalytic mechanism involves first ligand-based reduction and protonation steps followed by metal-centered processes.