Beyond Metal-Hydrides: Non-Transition-Metal and Metal-Free Ligand-Centered Electrocatalytic Hydrogen Evolution and Hydrogen Oxidation.
A new pathway for homogeneous electrocatalytic H2 evolution and H2 oxidation has been developed using a redox active thiosemicarbazone and its zinc complex as seminal metal-free and transition-metal-free examples. Diacetyl-bis(N-4-methyl-3-thiosemicarbazone) and zinc diacetyl-bis(N-4-methyl-3-thiosemicarbazide) display the highest reported TOFs of any homogeneous ligand-centered H2 evolution catalyst, 1320 and 1170 s(-1), respectively, while the zinc complex also displays one of the highest reported TOF values for H2 oxidation, 72 s(-1), of any homogeneous catalyst. Catalysis proceeds via ligand-centered proton-transfer and electron-transfer events while avoiding traditional metal-hydride intermediates. The unique mechanism is consistent with electrochemical results and is further supported by density functional theory. The results identify a new direction for the design of electrocatalysts for H2 evolution and H2 oxidation that are not reliant on metal-hydride intermediates.
University of Louisville , Department of Chemistry, 2320 South Brook Street, Louisville, Kentucky 40292, United States.
Andrew Z
AZ
Haddad
University of Louisville , Department of Chemistry, 2320 South Brook Street, Louisville, Kentucky 40292, United States.
Brady D
BD
Garabato
University of Louisville , Department of Chemistry, 2320 South Brook Street, Louisville, Kentucky 40292, United States.|Visiting Professor, Department of Food Sciences, Medical University of Gdansk , Al. Gen. J. Hallera 107, 80-416 Gdansk, Poland.
Pawel M
PM
Kozlowski
University of Louisville , Department of Chemistry, 2320 South Brook Street, Louisville, Kentucky 40292, United States.
Robert M
RM
Buchanan
University of Louisville , Department of Chemistry, 2320 South Brook Street, Louisville, Kentucky 40292, United States.
Craig A
CA
Grapperhaus