Metal‐NO ₂ Anchored Graphene Single‐Atom Catalysts for Hydrogen Evolution Reaction: A Density Functional Theory Study

The development of novel earth‐abundant, low‐cost electrocatalysts to efficiently drive the hydrogen evolution reaction (HER) is a key challenge for clean energy solutions. Using density functional theory (DFT), we systematically explored the structural stability, electronic properties, and catalytic performance of single‐atom catalysts (SACs) featuring transition metals (TM = Co, Cu, Fe, Mn, Ni) supported by an NO 2 functional group anchoring agent on a graphene sheet. The pristine TM–NO 2 SACs are energetically stable and exhibit a nonmagnetic metallic nature with no considerable difference between spin‐up and spin‐down channels, as confirmed by spin polarized calculations. To fully characterize interaction of adsorbed hydrogen on these catalysts, we found a metallic band nature, charge transfer from TM to H‐atom and magnetic behavior due to antisymmetric spin up and spin down states in the total density of states (TDOS). Ni, Co, and Cu based SACs, which possess moderate positive charges between +0.71 and +0.89 |e|, offers optimal HER catalytic performance. Interestingly, a deeper negative value of the d‐band center is found for H‐adsorbed Ni‐NO 2 SAC. Among all understudy systems, the Ni‐NO 2 SAC anchored on the graphene substrate exhibits the most favorable Δ G H* (−0.39 eV) for the HER mechanism. This approach offers a new platform for designing novel and cost‐effective candidate for the efficient HER catalytic process.