Atomic Layer Deposition of PdRux Alloy Nanoparticles for Hydrogen Evolution Reaction Electrocatalysis in Acidic Media

Abstract

Palladium (Pd) metal is considered a promising alternative to platinum (Pt) due to its similar hydrogen adsorption Gibbs free energy (ΔG_H). Alloying is a viable strategy to mitigate the suboptimal hydrogen evolution reaction (HER) electrochemical performance associated with the excessively strong Pd–H bonding interaction. This study focuses on synthesizing PdRu_x alloy nanoparticles on carbon cloth using a combination of atomic layer deposition (ALD) and annealing. By adjusting the number of Ru cycles from 100 to 500 on 200-cycle Pd on carbon cloth, a series of PdRu bimetallic nanoparticle samples were obtained by ALD. The subsequent annealing process was conducted at 600 °C in an argon atmosphere to facilitate the formation of PdRu_x alloy phases. The density functional theory (DFT) calculation results indicate that some surface configurations of the alloyed PdRu_x electrocatalysts are better than those of the single metal Ru or Pd, conducive to HER performance. Among them, the annealed 200-cycle Pd-400-cycle Ru alloy electrocatalyst exhibits the best electrocatalytic performance, with an overpotential of 35.6 mV at 10 mA cm^–2. Simultaneously, these PdRu_x alloy nanoparticles show excellent long-term stability with a 40 h chronopotentiometry test at 10 mA cm^–2 in acidic media. The enhanced catalytic performance is attributed to the nanoscale size effect of the PdRu_x alloy nanoparticles and the optimized electronic interaction between alloy components. These synergistic effects lead to a significant reduction in hydrogen binding energy (HBE), thereby substantially improving the HER activity. This work provides enormous potential for the development of highly efficient alloy electrocatalysts by the ALD method.