Atomic layer deposition of Pd nanoparticles and single atoms on self-supported carbon monolithic catalysts synergistically boosts the hydrogen evolution reaction†

The construction of highly active hydrogen evolution electrocatalysts is necessary to improve the efficiency of water electrolysis devices. Pt-based precious metal catalysts have been reported to have high activity, but their high cost and scarcity limit their further application. Herein, we constructed a monolithic electrode containing both Pd nanoparticles (NPs) and Pd single atoms (SAs) anchored on carbonized wood (CW) via atomic layer deposition (ALD). The optimal electrode obtained by adjusting the number of ALD cycles exhibited a lower overpotential of 50.5 mV at 10 mA cm⁻² and a smaller Tafel slope of 30.8 mV dec⁻¹ in alkaline electrolyte. Moreover, the optimal CW-Pd20 electrocatalyst was found to possess fast HER kinetics and excellent stability. Theoretical calculations illustrate that Pd NPs facilitated the decomposition of water, while the Pd SAs promoted the adsorption of H, thus leading to excellent HER activity of CW-Pd20.