Competitive Adsorption Stabilizes Metallic Copper for Anodic H2 Evolution from α-H Aliphatic Aldehydes

Coupling the cathodic hydrogen evolution with aldehyde oxidation at the anode lowers cell voltages and enables dual hydrogen production compared to conventional water electrolysis. Here, we expand the low-potential anodic oxidative dehydrogenation to aliphatic, α-hydrogen-containing aldehydes using acetaldehyde as a model molecule to demonstrate the concurrent formation of acetate and hydrogen, while identifying the mechanistic origins of the anodically formed hydrogen. In situ and ex situ characterization and density functional theory computations reveal that activity is controlled by an apparent competition between the acetaldehyde and hydroxide molecules over the catalytic sites. Specifically, hydroxide is crucial to enable aldehydic oxidation but also promotes the oxidation and deactivation of the employed copper-based catalyst, whereas acetaldehyde stabilizes the active sites and sustains turnover. Techno-economic analysis highlights economic viability and scalability potential. This work contributes to clean energy technologies by expanding the scope of oxidizable aldehydes for efficient hydrogen production and value-adding organic upgrade.