Thickness-dependent hydrogen evolution reaction activity on Pd films: an insightful view from magnetism

Abstract

Magnetism has been recently considered to be of great significance in boosting the hydrogen evolution reaction (HER) activity. In order to investigate the catalytic role of magnetism in the HER, numerous efforts mostly focus on doping magnetic elements in catalysts. However, some interfering factors such as strain and hybridization inevitably appear in this approach, which is not conducive to the study of the intrinsic relationship between magnetism and the HER. In this work, we propose a Pd thin film with thickness-dependent magnetism to explore the magnetism–activity correlation for the HER, significantly avoiding the interference of other factors. Our first-principles results show only the ferromagnetic 4 and 9 (monolayer) ML Pd films exhibit better HER activity than the nonmagnetic films with adjacent thickness, with a ΔG_H* value of −0.108 eV and −0.132 eV, respectively. The results revealed that it is the ferromagnetism of the Pd active site that weakens the strength of hydrogen adsorption and improves the amount of electron transfer, thereby resulting in enhanced magnetic HER activity. Hence, our work provides direct evidence for magnetism-improved HER activity, opening up new possibilities for the rational design and modulation of high-performance catalysts for the HER.