In collaboration with the group of Prof. Kelvin H. L. Zhang at XMU Xiamen, China within the mobility program of the Sino-German Center for Research Promotion and Dr. Freddy Oropeza from IMDEA energy in Madrid, the phase transformation of NiS during the HER was investigated. The results are now available as an open access article in Nature Communications.

Transition metal chalcogenides are promising electrocatalysts for the HER, characterized by their availability, scalable preparation and electrochemical performance. However, the starting materials are often transformed under operating conditions, which is not yet understood in detail, nor is the reaction mechanism. This is the focus of this study and addressed by means of operando spectroscopy (XAS & Raman) and NAP-XPS experiments.

It is shown how NiS transforms in operation to a Ni3S2 support with NiO clusters. This system proves to be electrocatalytically very active. Furthermore, it is successfully investigated how hydrogen formation is accelerated. The interface (O-Ni-S) plays a decisive role. By splitting water molecules at nickel sites, the further reaction can quickly progress at the neighboring sulfur site.