Size and doping effects on the HER performance in Ag and Cu clusters

Turning non-precious metals into efficient catalysts for the hydrogen evolution reaction (HER) presents both fundamental challenges and significant technological implications. Metal nanoclusters (MNCs) exhibit considerable potential to achieve this objective due to their quantum size effects and low-coordination environments. In this study, we comprehensively investigate the size and doping effects of silver (Ag) and copper (Cu) clusters using first-principles density functional theory (DFT). Our findings indicate that the adsorption free energies of hydrogen on both Cu and Ag clusters are enhanced compared to their periodic surface counterparts, leading to significantly improved HER performance. Specifically, for Cu clusters, Cu ₅₅ demonstrates the best HER performance with a hydrogen free energy (ΔG _H ) of only − 0.02 eV at hollow sites. In contrast, Ag ₁₃ exhibits the best HER performance among Ag clusters, with a ΔG _H of -0.04 eV at bridge sites. The incorporation of nickel (Ni) and platinum (Pt) weakend the hydrogen adsorption energy of the Cu ₁₃ cluster, resulting in improved HER performance for Cu ₁₃ . Partial density of states (PDOS) analysis reveals that as we transition from bulk materials to clusters, the density of states around the Fermi energy increases due to quantum confinement effects, thereby enhancing hydrogen binding ability. Also, the doping of Ni and Pt in Ag and Cu cluster can shift the position of d-band center effectively and tune the hydrogen binding ability. Furthermore, Bader charge analysis indicates that charge accumulation on the Pt and Ni-doped clusters increases with cluster size. This research provides valuable insights into optimizing catalytic activity for hydrogen adsorption across different cluster sizes, as well as in Ni and Pt-doped Cu and Ag nanoclusters in the context of HER.