Surface selectivity of Ni3S2 toward hydrogen evolution reaction: a first-principles study

Abstract

Exploring materials with high catalytic performance toward hydrogen evolution reaction (HER) is of importance for the development of clean hydrogen energy, and their surface structure is essential for this function. In this study, using density functional theory (DFT), we reported a comprehensive study on the phase stability, surface structures, electronic properties and HER catalytic properties of the low-index surfaces of Ni₃S₂, including the (0001), (100), (101), (110) and (111) planes with different terminations. Our calculated results demonstrate that S-rich surfaces and several stoichiometric surfaces of Ni₃S₂ are thermodynamically stable, including (0001)A, (100)A, (110)C, (100)C, (100)B and (111)A surfaces. Among the six stable surface structures, the (0001)A, (100)B and (100)C surfaces of Ni₃S₂ are indispensable for high HER performance because of their high catalytic activity, suitable potential and high thermodynamic stability. The calculated changes of Gibbs free energy (ΔG_H*) of the Top S2 site on (0001)A, Hollow Ni₂S₃S₄ site on (100)C, and Bridge Ni₁Ni₃ site and Hollow Ni₂S₁S₂ site on (100)B are −0.143, 0.122, 0.012, and −0.112 eV, respectively, comparable with or even better than those of Pt(111) (−0.07 eV). In addition, the possible Volmer–Heyrovsky and Volmer–Tafel processes on the considered surfaces are also investigated. When the overpotential is in the range of 0 to 300 mV, the density of active sites on the (100)B surface of Ni₃S₂ is found to be the highest. This work provides significant insights on the surface selectivity of Ni₃S₂ toward HER and provides a route to optimize the performance of Ni₃S₂ with exposed surfaces.