Palladium-doped bimetallic sulfide spinel nano-electrocatalyst grown on nickel foam for efficient green hydrogen production validated by first principal DFT study

Cost-effective and highly efficient bifunctional electrocatalysts for green hydrogen production, especially those based on chemical composition adjustment, are crucial for preserving a pollution-free natural environment. In this work, a unique Pd-doped ZnCo₂S₄ coated Nickel foam as ZnPd_xCo_2-xS₄ (0.00≤x ≤ 0.10)@NF nano electrocatalyst was synthesized successfully via a two-step hydrothermal approach. The microstructure was analyzed using the XRD, SEM, TEM, HR-TEM, and XPS techniques. The electrocatalyst ZnPd_xCo_2-xS₄ (0.00≤x ≤ 0.10)@NF nano electrocatalyst demonstrated improved performance in the HER, with an overpotential of 166 mV, a calculated Tafel slope of 127.7 mV/dec, and sustained stability lasting over 40 h, as determined by chronopotentiometry methods. The electrochemical analysis of the nano electrocatalyst with a 6.0 % Pd⁴⁺ doping concentration demonstrated enhanced performance toward the HER process. These noticeable improvements can be attributed to a much higher ECSA (27.0 cm²) and quicker charge transfer kinetics at the interface between the semiconductor and the electrolyte. Furthermore, our DFT calculations reveal that Pd sites on the ZnPd_xCo_2-xS₄ catalyst, with a near-thermoneutral energy barrier of −0.12 eV, enhance water dissociation and facilitate the Volmer step. The electronic properties further reveal that the Pd dopant tunes the electronic configuration, creating a synergistic effect among active sites and accelerating HER kinetics. This noble metal (Pd) dopant tuning significantly improved the catalyst's performance for hydrogen evolution reactions.