Synergistic effect of Pd single atoms and nanoparticles deposited on carbon supports by ALD boosts alkaline hydrogen evolution reaction

The synergistic effects between carbon supports and noble metal species of an electrocatalyst are known to effectively boost the alkaline hydrogen evolution reaction (HER). Herein, Atomic Layer Deposition (ALD) was employed to decorate carbon papers with Pd species comprising single atoms (SAs) and nanoparticles (NPs). Transmission electron microscopy analysis revealed the metallic nature and coexistence of Pd as SAs and NPs. The results of X-ray photoelectron spectroscopy supported the evidenced SA species, manifested as the Pd+2. An increase in the electrochemical active surface area from 12.98 to 413.48 cm−2 was evidenced with increasing ALD cycles from 30 to 300c Pd and remained unchanged until 600c Pd. The exceptional overpotential for CP 600c Pd exhibits the lowest value of 4.55 mV, compared to previous reports for Pd electrocatalysts in a non-acidic environment, and confirms the synergistic effect of Pd SAs and NPs that plays a major role in enhancing alkaline HER.