Electroreduction of carbon dioxide (CO₂) over copper-based catalysts provides an attractive approach for sustainable fuel production. While efforts are focused on developing catalytic materials, it is also critical to understand and control the microenvironment around catalytic sites, which can mediate the transport of reaction species and influence reaction pathways. Here, we show that a hydrophobic microenvironment can significantly enhance CO₂ gas-diffusion electrolysis. For proof-of-concept, we use commercial copper nanoparticles and disperse hydrophobic polytetrafluoroethylene (PTFE) nanoparticles inside the catalyst layer. Consequently, the PTFE-added electrode achieves a greatly improved activity and Faradaic efficiency for CO₂ reduction, with a partial current density >250 mA cm⁻² and a single-pass conversion of 14% at moderate potentials, which are around twice that of a regular electrode without added PTFE. The improvement is attributed to a balanced gas/liquid microenvironment that reduces the diffusion layer thickness, accelerates CO₂ mass transport, and increases CO₂ local concentration for the electrolysis.

Polymeric humin formation greatly diminishes levulinic acid yields in acid treatment of C6 sugars in aqueous medium. Protecting reactive functional groups of sugars and reaction intermediates via acetalisation and etherification in methanol medium effectively suppresses humin formation and remarkably enhances the production of levulinic esters.