The design of highly efficient, low-cost and long-term stable electrocatalysts for the hydrogen evolution reaction (HER) is a research hotspot in the field of sustainable energies (e.g., fuel cells). In this study, a novel catalyst design comprising NiO₂ supported Pd nanocatalysts (NCs) with an interfacial atomic cluster of Ni metal is proposed and their HER activity with the corresponding reaction mechanism is systematically investigated by using density functional theory (DFT) calculations. For the optimum case with four Ni atoms in a tetragonal shape (i.e., NiO₂–Ni₄–Pd), the reaction coordinate (barrier) is reduced by 0.36 eV and 0.34 eV respectively in the Volmer and Tafel steps among models with different amounts of Ni atoms. The corresponding results reveal that the novel steric confinement effects of the atomic Ni-ensemble tetragon will unbalance the surface charge distribution to generate the local domain heterogeneity on the Pd-shell surface and further prove the doping threshold of the Ni tetragon in terms of HER-kinetics improvement. For evaluating the rationales on experimental variations by the inevitable interatomic intermix in a rapid crystal growth process, the results of various atomic doping ratios of Ni_d/Pd from ∼2% to 67% are systematically investigated. The adsorption energy of H* is even lower than that on Pt by further increasing Ni atoms to 32, therefore, showing the potential capability of such a type of structure design for catalysts in the HER. Based on the presented results, we believe that our research can be applied to guide the adjustment of heterogeneous catalysts in the experimental synthesis while offering a theoretical insight for designing transition metal oxide-based systems toward inexpensive, efficient and green initiative merits.

The development of electrocatalysts with reconcilable balance between the cost and performance in oxygen reduction reaction (ORR) is an imperative task for the widespread adoption of fuel cell technology. In this study, we proposed a unique model of diatomic Pt-cluster (Pt-dimer) in the topmost layer of the Co/Pd bimetallic slab (Co@Pd–Pt₂) for mimicking the Co_core@Pd_shell nanocatalysts (NCs) surface and systematically investigating its local-regional collaboration pathways in ORR by density functional theory (DFT). The results demonstrate that the Pt-dimer produces local differentiation from both ligand and geometric effects on the Co@Pd surface, which forms adsorption energy (E_ads) gradients for relocating the ORR-adsorbates. Our calculations for E_ads-variations of ORR-species, reaction coordinates, and intraparticle charge injection propose and confirm a novel local synergetic collaboration around the Pt-dimer in the Co@Pd–Pt₂ system with the best-performing ORR behavior compared with all reference models. With proper selection of the composition in intraparticle components, the proposed DFT assessments could be adopted for developing economical and high-performance catalysts in various heterogeneous reactions.

The crux of the hot topic concerning the widespread replacement of fuel cells (FCs) with traditional petrochemical energy is to balance improving the oxygen reduction reaction (ORR) and reducing the cost. The present study employs density functional theory (DFT) to investigate the effect of Pt ensemble size regulation from a single atom to full coverage on the physio-chemical properties, oxygen adsorption energies and overall ORR efficiency of bimetallic nanocatalysts (NCs) with a Co_core–Pd_shell structure. Our results reveal that the electronegativity difference and lattice strain between neighboring heteroatoms are enhanced to trigger a synergetic effect in local domains, with the Pt cluster size reduced from nanometers to subnanometers. They induce a directed and tunable charge relocation mechanism from deep Co to topmost Pt to optimize the adsorption energies of O₂/O* and achieve excellent ORR kinetics performance with minimum Pt usage but maximum Pt atom utilization (i.e., Pt₁ to Pt₃) compared with benchmark Pt(111). Such a dependency between the cluster size and corresponding ORR performance for the established Co@Pd–Pt_n system can be applied to accurately guide the experimental synthesis of ordered heterogeneous catalysts (e.g., other core@shell-clusters structures) toward low Pt, high efficiency and green economy.