Unveiling the mechanism of high-performance hydrogen evolution reaction on noble-metal-free (113)-faceted Ni(3)C: ab initio calculations

To examine the reactivity of noble-metal-free Ni(3)C towards hydrogen evolution reaction (HER), we report a comprehensive first-principles density functional theory (DFT) study on the stability, geometric structure, electronic characteristics, and catalytic activity for HER on the Ni(3)C crystal (113) surfaces with different surface terminations, namely the C-rich and Ni-rich terminated surface of Ni(3)C (113). The results indicate that C-rich and some stoichiometric surfaces are thermodynamically stable. The bridge-site of C-rich Ni(3)C (113) is indispensable for HER because it not only displays improved electrocatalytic activity, but also possesses appropriate hydrogen adsorption energy, overpotential and robust stability. The ΔG(H) (0.02 eV) and overpotential obtained by C-rich Ni(3)C outperformed that obtained by Pt determined by computation (ΔG(H) = −0.07 eV). Thus, the bridge-sites of C-rich Ni(3)C (113) function as both excellent and stable active sites and adsorption/desorption sites. Increasing the density of active sites through doping or enlarging the surface area renders a prospective strategy to ameliorate the HER activity further. Overall, this study elucidates new insights into the surface properties of Ni(3)C for HER from water splitting and opens up a fascinating avenue to optimize the performance of solar energy conversion devices by synthesizing preferentially exposed catalyst facets.