While many possibilities have yet to be explored for CO2 reduction, a gas-diffusion layer provides a porous electrode structure which fundamentally changes both reagent and product transport pathways compared to the impermeable supports traditionally used in fully-aqueous reactors. As adoption increases substantial opportunity then exists for further innovative catalyst-support integrations to improve either stability or performance. The subtle operational difference also means the traditionally described benefits of catalyst nanostructuring (for increased surface area, mass transport, facet exposure, etc.) have to be somewhat reassessed, which may be difficult as the primary active surface is no longer easily accessible to surface characterization techniques.