Chemical environment effects on the electrochemical performance and thermal stability of PdCu3 nanoparticles in HER cathodic electrodes

Highlights: • Cu 2p_3/2 XPS peak is a perfect chemical environment probe for PdCu₃ HER electrodes. • The presence of Cu–F bonds on PdCu₃ nanoparticles surfaces hinders HER. • CuO improves the number of active sites available for HER. • Methodology leads to economically viable copper rich Pd–Cu HER electrodes. The need for diversification of the worldwide industrial matrix encourages the use of cleaner and renewable electrical power sources, such as hydrogen fuel cells. Water electrolysis for H₂ production is an efficient process but it demands the development of resourceful, low-cost electrocatalysts for the hydrogen evolution reaction (HER). This work aims to apply carbon supported PdCu₃ nanoparticles as electrocatalysts in HER, seeking to understand the influence of atomic chemical environment changes on their activities. Since thermal treatments affect chemical bonds, thus electrodes produced with these nanocatalysts are heated either in air or under vacuum. XPS (X-ray photoelectron spectroscopy) yields precise information on metallic sites evolution, and our analyses infer that thermal treatment in air favours the formation of Pd–O bonds and a strong Cu oxidation. Concomitantly, these electrodes achieve the highest exchange current density and improved catalytic activity. In contrast, the electrodes treated in vacuum form Cu–F bonds and exhibit low activity. These findings strongly indicate that our methodology leads to economically viable copper rich Pd–Cu electrodes, whereas the presence of CuO on the nanoparticles surfaces is a key factor for their improved activity owing to Cu leaching and/or CuO metallization mechanism during HER, and consequent Pd-enrichment of the nanoparticles.