Author: Younes Abghoui (University of Iceland) - The transition towards a sustainable energy economy relies heavily on the development of clean hydrogen production technologies. Among these, electrochemical water splitting, driven by the hydrogen evolution reaction (HER), represents a key process for generating hydrogen fuel without carbon emissions. However, a major challenge impeding large-scale deployment of water electrolysis is the heavy dependence on platinum-group metal catalysts, which are both scarce and expensive. Consequently, there is a pressing need to discover and design alternative catalysts that are both abundant and cost-effective while maintaining high catalytic efficiency. In this study, we address this challenge through a comprehensive computational investigation into the potential of Hafnium-based materials as efficient HER catalysts. Using density functional theory (DFT) calculations, we systematically explore the catalytic properties of Hafnium surfaces for HER. Hafnium, a group IV transition metal, offers an attractive combination of chemical robustness, corrosion resistance, and unique electronic characteristics that may favor proton adsorption and hydrogen evolution. We focus our analysis on determining the hydrogen adsorption free energy (ΔG_H*), which is a critical descriptor for HER activity, as optimal performance is typically associated with ΔG_H* values close to thermoneutral (near zero). In addition to evaluating ΔG_H* values, we also assess surface stability under electrochemical conditions to ensure the material can operate reliably during prolonged water splitting applications. The study considers various low-index facets of Hafnium to capture facet-dependent behavior, an important factor given that different crystallographic surfaces can exhibit significantly different catalytic performances. Reaction pathways for hydrogen formation are mapped, with particular attention given to the thermodynamic and kinetic aspects of the reaction mechanisms.
