Green and sustainable bipolar hydrogen production via formaldehyde-water Co-electrolysis enabled by a Pd@NiCo/CC electrocatalyst

We report a sustainable and efficient Pd@NiCo/CC electrocatalyst for green hydrogen production through formaldehyde-water co-electrolysis. The catalyst combines palladium, nickel, and cobalt to create synergistic effects, demonstrating exceptional performance for the formaldehyde oxidation reaction (FOR) at just 0.32 V vs. reversible hydrogen electrode (RHE) while simultaneously generating hydrogen at both the anode and cathode with 95.7 % Faradaic efficiency for hydrogen and formate production. The catalyst design achieves this performance with reduced precious palladium loading compared to conventional Pd-based catalysts. Theoretical insights from density functional theory (DFT) calculations reveal that palladium incorporation effectively lowers the energy barrier for C –H bond cleavage. This electronic structure modulation contributes to the observed high activity and stable operation for over 8 h. The enhanced catalytic performance originates from the well-defined synergistic roles of its components. Palladium provides the primary active sites for C –H bond cleavage in formaldehyde. The NiCo bimetallic framework promotes electronic conductivity, facilitates charge transfer to Pd, and helps stabilize the metallic state of Pd under reaction conditions. Moreover, the interfacial electronic interactions between Pd and NiCo lower the energy barrier of the rate-determining step, as confirmed by DFT calculations. This work presents an alternative approach to renewable hydrogen generation that reduces energy requirements and eliminates greenhouse gas emissions, suggesting the potential for developing more sustainable electrocatalysts for clean energy applications. • Sustainable H 2 production via formaldehyde-water co-electrolysis at 0.32 V with 95.7 % Faradaic efficiency. • Pd@NiCo/CC catalyst reduces Pd loading and lowers the C –H cleavage barrier by 56 % via synergistic effects. • Bipolar H 2 generation with formate byproduct achieves 40 % energy savings vs. conventional electrolysis. • Stable 8-h operation with 92 % activity retention, enabled by NiCo-enhanced electron transport. • DFT confirms interfacial charge redistribution boosts kinetics, enabling near-100 % reactant utilization.