Selective electrochemical oxidation of gaseous acetaldehyde to liquid acetate at Ni(OH)₂-based gas-solid interface

Gaseous acetaldehyde (AA) is a hazardous volatile organic compound and a critical precursor in the formation of secondary organic aerosols and tropospheric ozone. Conventional AA abatement strategies rely on complete oxidative mineralization to CO₂, which results in significant carbon loss and secondary environmental burdens. In this study, we developed a gas-phase electrochemical oxidation strategy that enables the direct and selective conversion of gaseous AA to liquid-phase acetate at the gas-solid-electrolyte interface, under ambient conditions, without CO₂ evolution or downstream separation processes. The electrochemical cell employed a Ni(OH)₂-based anode, coupled with a semi-solid gel electrolyte and an anion exchange membrane to facilitate efficient charge transfer and product compartmentalization. Under optimized operational conditions (500 ppmv AA, 25 mL min⁻¹, 5 mA cm⁻²), the system achieved 84 % AA removal and 92.2 % carbon recovery, with a low energy consumption of 20.5 g kWh⁻¹. In situ ATR-FTIR spectroscopy and electrochemical analysis revealed that the oxidation proceeds via the formation of a diolate intermediate at electrochemically generated Ni³⁺(O)OH active sites, enabling C[sbnd]C bond-conserving oxidation pathways. Potassium acetate (CH₃COO⁻K⁺) was identified as the exclusive carbonaceous product in the catholyte. Long-term stability testing over 168 h confirmed sustained performance at a constant cell potential of 1.5 V, with negligible degradation. This work demonstrates a scalable and energy-efficient platform for VOC valorization, offering a sustainable alternative to conventional oxidation routes.