context: Gas diffusion electrodes (GDEs) were fabricated by spraying a catalyst ink made from polynorbonene tetrablock copolymer powder ionomers (GT32 and GT73) and Pt-based electrocatalysts onto Toray TGP-H-060 gas diffusion layers (GDLs) with 5% PTFE. Commercially available 40% Pt/C (Alfa Aesar HiSPEC 4000, Pt nominally 40% wt, supported on Vulcan XC-72R carbon) was used at the cathode and 60% Pt–Ru/C (Alfa Aesar HiSPEC 10000, Pt nominally 40 wt%, and Ru, nominally 20 wt%, supported on Vulcan XC-72R carbon) was used as the anode. The detailed procedure for ink formulation and GDE fabrication has been previously reported, though a brief description is provided below.