Steering acidic CO2 electroreduction to ethanol via interfacial H-bond-mediated proton transport

Novel Cu/CNTs-OH interface decouples gas/ion transport for acidic CO 2 conversion. • Interfacial H-bond network via -OH groups enhances proton mobility. • Shifts selectivity from ethylene to ethanol by optimizing *H coverage and proton supply. • In situ and theoretical evidences link H-bond network to key intermediates in ethanol pathway. Electrocatalytic CO 2 reduction (ECR) offers a route to convert CO 2 into valuable fuels such as ethanol, which is favored for its high energy density and ease of storage. ECR in acidic media could suppress carbonate formation but intensify competition from the hydrogen evolution reaction, limiting the selectivity of C 2+ products. Here we introduce an interfacial H-bond network strategy by coupling Cu nanoparticles with hydroxylated carbon nanotubes (CNTs-OH) to construct proton supply and steer reaction pathways for acidic CO 2 -to-ethanol electroconversion. Molecular dynamics and distribution of relaxation times analysis show that CNTs-OH enhance CO 2 diffusion while surface -OH groups form a dynamic H-bond network, facilitating proton transport via the Grotthuss mechanism. Density functional theory (DFT) calculations, isotope labeling, and rotating disk electrode results confirm that CNTs-OH promote water dissociation, supplying protons to Cu sites. In situ spectroscopy links the H-bond network to key ethanol pathway intermediates. Consequently, the introduced H-bond network at the electrode interface yields a 2.5-fold enhancement in ethanol selectivity and a dramatic shift in the ethanol/ethylene ratio from 0.4 to 1.6. This work provides an effective materials design strategy and mechanistic insight for selective CO 2 -to-ethanol conversion in acid media.