Immobilizing Molecular Metal Dithiolene–Diamine Complexes on 2D Metal–Organic Frameworks for Electrocatalytic H<inf>2</inf>Production

Abstract

Carbon electrocatalysts consisting of metal complexes such as MNxor MSxare promising alternatives to high-cost Pt catalysts for the hydrogen evolution reaction (HER). However, the exact HER active sites remain elusive. Here, molecular metal dithiolene-diamine (MS2N2, M=Co and Ni), metal bis(dithiolene) (MS4), and metal bis(diamine) (MN4) complexes were selectively incorporated into carbon-rich 2D metal–organic frameworks (2D MOFs) as model carbon electrocatalysts. The 2D MOF single layers, powders, and composites with graphene were thus prepared and showed definite active sites for H2generation. The electrocatalytic HER activity of the 2D MOF-based catalysts with different metal complexes follow the order of MS2N2>MN4>MS4. Moreover, the protonation preferentially occurred on the metal atoms, and the concomitant heterolytic elimination of H2was favored on the M–N units in the MS2N2active centers. The results provide an in-depth understanding of the catalytic active sites, thus making way for the future development of metal complexes in carbon-rich electrode materials for energy generation.