Hydrophobized electrospun nanofibers of hierarchical porosity as the integral gas diffusion electrode for full-pH CO 2 electroreduction in membrane electrode assemblies

Conventional gas diffusion electrodes (GDEs) in the laminate configuration have witnessed great success in boosting up the productivity of electrocatalytic CO 2 reduction, but still suffer from issues of delamination, flooding, salt precipitation, and limited utilization of active sites. Herein, an integral GDE (NiNF) with hierarchical porosity is fabricated through electrospinning, comprising CNT-reinforced carbon nanofibers embedding undercoordinated Ni–N–C active sites. These nanofibers are thermally treated with polytetrafluoroethylene (PTFE) to append a superficial hydrophobic layer, enabling the GDE to work in a broad pH range in both flow cells and membrane electrode assembly (MEA). In virtue of the integral architecture, hierarchical porosity and highly active catalytic sites, the optimized NiNF GDE achieves a near-unity faradaic efficiency of CO, affording peak current densities of 282 ± 9 and 362 ± 10 mA cm −2 in alkaline and acidic flow cells, respectively. What's more, the hydrophobized integral GDE showcases stable operation for more than 273 hours with a total energy efficiency of 38% in neutral MEA and a single-pass CO 2 conversion of 78% in acidic MEA. This work paves the way for industrial-scale CO 2 electrolysis through the innovation of GDE design.