Synergistic effect of S-bridged Fe-Ni group on hydrogen evolution for pentlandite.

Pentlandite is reported to exhibit good catalytic activity in hydrogen evolution reaction (HER). Many studies have paid attention to metal catalysis of pentlandite. However, the nonmetal catalysis is not considered for HER. Here, we unravel one probable catalytic mechanism of pentlandite toward HER using density functional theory. In our study models, (001) and (100) surfaces are created because there are three types of S-bridged M-M groups on them. Our study reveals that (Fe-Ni)-S center has a moderate value of Gibbs free energy while the corresponding value for (Fe-Fe)-S or (Ni-Ni)-S center is largely positive or negative. In (Fe-Ni)-S group, Fe and Ni can regulate the antibonding state of S, and then balance adsorption and desorption of proton. In addition, an intrinsic electronic potential difference exists between Fe and Ni in (Fe-Ni)-S group, which may boost the charge transfer. Particularly, (Fe-Ni)-S groups are perpendicular to the surface, and four of them make up one closed loop in the surface. It is suggested that the behaviors of such configuration composed of reaction centers resemble edge sites along the layers of MoS toward HER. This study provides a deep insight into the synergistic effect of S-bridged Fe-Ni groups and enables the modulation of electrocatalytic reaction of pentlandite toward HER.