Hydrophobized electrospun nanofibers of hierarchical porosity as the integral gas diffusion electrode for full-pH CO2 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 CO2 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 CO2 conversion of 78% in acidic MEA. This work paves the way for industrial-scale CO2 electrolysis through the innovation of GDE design.