Unravelling the factors that control the activity and stability of catalysts for alkaline water electrolysis

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Green hydrogen is an important energy vector in our transition to a net-zero future. Almost all green hydrogen produced today is from alkaline water electrolysis. Earth-abundant catalysts based on NixOyHz are used as catalysts for the cathodic hydrogen evolution reaction. Although alkaline electrolysers are a mature technology, very little is known about the origin of the activity and stability of NixOyHz catalysts used in industrial electrolysers1,2. It has been reported that for the cathodic hydrogen evolution reaction, the overpotential increases by approximately 0.35 V during the first 40 hours of operation. This drop can be prevented by incorporating Fe into the lattice3. However, it is not clear whether the active catalytic phase is an oxide, a metal or a hydride1. Moreover, the cycling and steady state conditions that trigger and/or amplify the deactivation is unknown. Gaining such insights would allow us to determine the limits to activity and stability of non-precious metal-based catalysts for hydrogen evolution and to design better catalysts that outperform the current state-of-the-art. In this project, the student will synthesise NixOyHz and Fe-doped NixOyHz catalysts and perform electrochemical activity and stability tests for a range of different operation protocols. The samples will be characterised using X-ray absorption and X-ray photoemission spectroscopy to determine the oxidation state of the metal centre and surface intermediates as a function of potential as well as neutron diffraction and atom probe tomography to determine the morphologies, particularly the presence of (oxy)hydroxide or hydride phases.