Second-row transition metals decorated cyclo[18]carbon: Single-atom catalysts for excellent hydrogen evolution reaction

To fulfill the huge demand of clean and sustainable energy, scientists are keenly investigating cost-efficient, readily accessible and effective catalysts to replace Pt-based catalysts in hydrogen evolution reaction (HER). Currently, the scientific community has a growing interest in the quest for suitable support for single-atom catalysts (SACs). Here, we have explored the application of cyclo[18]carbon (C18 nanocluster) as a support for the second-row transition metals (TMs) based SACs for HER activity. We have analyzed the geometry, electronic properties, stability and catalytic performance of TMs@C18 SACs for HER activity. The high binding energy values confirmed the stability of SACs. Moreover, structure alterations, changed dipole moments, shifting of electron density towards the adsorption sites and Mulliken charge transfer proved the strong binding of TMs with C18 nanocluster. The decoration of TMs over C18 nanocluster enhances the conductivity of C18 nanocluster. The catalytic performance is best in the Tc@C18, Ru@C18 and Rh@C18 SACs with Gibbs free energy (ΔGH) values of 0.18 eV, −0.18 eV and −0.07 eV, approaching the ideal value. Our findings suggest that Tc@C18, Ru@C18 and Rh@C18 are highly stable and efficient SACs for HER.