CL20250616_003_#18_Co3O4Nps_CV_5mVpers_initial_seq2_20_PEIS_C01

ELab Identifier: , Preparation Procedure: The Co₃O₄ nanoparticle electrodes with a small catalyst loading were fabricated by spin-casting (Laurell WS-400BX-6NPP/LITE) 20 µL of Co₃O₄ ink at 4000 rpm for 5 min onto a gold-coated quartz crystal microbalance (QCM, BeamTech) resonator, which served as the current collector. The ink was prepared by dispersing Co₃O₄ nanoparticles (cpy_131_repro_calc) in Milli-Q water to achieve a concentration of 0.1 mg mL⁻¹. The exact catalyst loading cannot be directly derived from the dispersion’s concentration and cast volume. It is, however, approximated to be 1.7 µg cm⁻² at the maximum, as excess solution is expelled from the substrate during spinning.