Us1828

The same catalyst ink in the H-cell studies was used as 0% PTFE-catalyst ink here. The PTFE-dispersed catalyst layer was prepared as follows. First, 6 mg of commercial Cu nanoparticles (US1828, US Research Nanomaterials) and 6 mg of Vulcan XC 72 carbon black (Fuel Cell Store) were each dispersed in 1 mL isopropanol, respectively. Then, 2.2, 8.7, 20, 30, and 46.7 mg PTFE nanopowder (APS 30−40 nm, Nanoshel LLC) were dispersed in 2 mL isopropanol, respectively. After sonication for 1 h, Cu nanoparticle dispersion, carbon black dispersion, corresponding PTFE dispersion, and 200 μL Nafion solution (5 wt%, containing ~8 mg Nafion) were mixed and sonicated for another 1 h, which were used as 10%, 30%, 50%, 60%, and 70% PTFE-catalyst inks, respectively. Each catalyst ink was sprayed on an AvCarb GDS2230 substrate with a Cu catalyst loading of 0.65 ± 0.05 mg cm⁻². After drying overnight, 1 mL of diluted Teflon PTFE DISP 30 solution (0.12 wt%, Fuel Cell Store) was further sprayed on top of all electrodes except the 0% PTFE one. All the samples were dried in air for at least 5 h before testing.

First, 6 mg of commercial Cu nanoparticles (US1828, US Research Nanomaterials) and 6 mg of Vulcan XC 72 carbon black (Fuel Cell Store) were each dispersed in 2 mL isopropanol, respectively. After sonication for 1 h, the two dispersions were mixed with 200 μL Nafion solution (5 wt%) and sonicated for another 1 h. The mixture was used as the catalyst ink and sprayed on electrode substrates by a homemade XY plotter equipped with an airbrush. Two types of substrates with an area of 1 × 1 cm² were used: AvCarb MGL370 and AvCarb GDS2230 (Fuel Cell Store). After deposition, the electrodes were dried overnight at room temperature, with a Cu catalyst loading of 0.65 ± 0.05 mg cm⁻².