Graphene transition layer between monolithic carbon support and electroactive Pd catalysts in asymmetric electrodes for accelerated hydrogen evolution reaction kinetics

The requirement for surface wetting to enhance efficient electrolysis reactions, along with the need for dewetting to accelerate H 2 desorption from the electrode surface, creates a paradox in effective electrode design. In this study, we created an asymmetric hydrogen evolution reaction (HER) electrode that synergizes mass transfer and reaction processes on both sides. Using plasma-enhanced chemical vapor deposition (PECVD) and atomic layer deposition (ALD), we fabricated an asymmetric self-supported electrode (CW-GNs-Pd) on carbonized cedar wood. This electrode features a graphene-coated side with high roughness, enhancing superhydrophobicity for efficient hydrogen bubble desorption, while the uncoated side retains the natural porous structure for rapid mass transfer. Pd single atoms and nanoclusters were deposited on the graphene surface via ALD,modifying the electronic structure of the Pd active sites, as confirmed by XPS (Pd 3d peaks) and XAS (Pd K-edge absorption). The CW-GNs-Pd electrode demonstrates exceptional HER performance in both alkaline and acidic environments, achieving low overpotentials of 29 mV and 45 mV at 10 mA cm −2 , with Tafel slopes of 24.73 mV dec −1 and 10.11 mV dec −1 , respectively. It also shows remarkable stability over 120 h. The unique design, which separates mass transfer and catalytic zones, addresses traditional electrode limitations and presents a promising strategy for developing cost-effective, high-performance HER electrodes.