Selective electrosynthesis of 1,3-butadiene by tailoring the coverage of acetylene and water

1,3-Butadiene (C₄H₆), the main raw material for producing important chemicals (nylon, synthetic resin, rubber), relies on petroleum cracking with intensive carbon emissions. The electrocatalytic dimeric hydrogenation of natural gas/coal-derived C₂H₂ to C₄H₆ provides a nonpetroleum pathway. However, C₄H₆, as a byproduct of C₂H₂ hydrogenation, is usually neglected because of its very low Faradaic efficiency. Here, we theoretically and experimentally report a mechanism comprising acetylene dimerization and subsequent hydrogenation. The first dimerization process can be accelerated under appropriate coverage of acetylene and water. A ligand-modifying strategy is subsequently proposed to regulate the wettability of Cu nanoarrays to enable suitable coverages. The optimized 1-dodecanethiol-modified Cu nanoarrays deliver a 65.3% C₄H₆ Faradaic efficiency at 100 mA cm^-2. The C₄H₆ formation kinetics become sluggish at the two ends of the surface C₂H₂/H₂O ratios, and moderate C₂H₂/H₂O coverage accelerates the C‒C coupling process to promote C₄H₆ production. Moreover, life cycle assessment demonstrates its sustainability.