Low-Coordinate 3d Metal Complexes as Alternatives to Platinum Group Metals for Hydrogen Evolution Reaction

The production of hydrogen through the reduction of water via the Hydrogen Evolution Reaction (HER) is promising sustainable alternative to the use of hydrocarbon feedstocks. The current state of the art uses platinum as it operates at low overpotential with high turnover frequencies. However, the low abundance of platinum (37 ppb in the Earth's crust) leads to high economic and environmental cost, and its high toxicity leads to the production significant waste streams. The use of alternative catalysts featuring earth abundant metals that exhibit low cost, high natural abundance, uniform global distribution and low toxicity is essential to improving the sustainability of this reaction, and therefore as a source of hydrogen. Catalysts featuring cobalt are excellent candidates for this reaction, where mechanistic studies of the HER evolution reaction have identified key processes such as the protonation of CoI to CoIII-H species as key intermediates in the formation of H-H bonds.
This project will develop a range of cobalt(I) organometallic complexes as single metal HER catalysts, where the metal centre is stabilised using highly sterically encumbering ligands. These unique complexes have never been investigated for HER chemistry, despite their favourable redox chemistry and substrate binding environment. The cobalt(I) compounds will be investigated for their redox chemistry and sensitivity to acid, along with their electrochemical response in the HER conditions. Information gained from this investigation will allow us to develop the ligand design in order to improve the reaction. The student will benefit from training in synthetic chemical techniques (e.g. organometallic chemistry, spectroscopy, crystallography and kinetic investigations) and electrochemistry. Determination of reaction mechanisms through spectroscopic, structural and kinetic investigations allows the optimisation of the reactions. We anticipate that such investigations will also allow improvements in the reaction conditions and catalyst loadings required for hydrogen release.
Deliverables
-New earth abundant catalysts for HER
-Mechanistic understanding for these reactions, and information to inform catalyst/ligand design in HER
-Optimisation of HER reactions