Scheme 1. Schematic structure of the GDE at different binder contents. Without binder, the catalyst layer is flooded (A), as it is also indicated by the contact angle measurements, shown in Fig. 2A. At optimal binder content, the reactant CO reaches the catalyst surface, and the formed products leave the cell with the remnant CO gas (B). At too high binder content, the CO reactant cannot reach the catalyst surface, therefore, H2 evolves at the catalyst/liquid electrolyte interface (C).
