Next, we moved to cast our NiNC-IMI and NINC-PANI catalysts into cathode layers of single cell electrolyzers using spray-coating of aqueous inks. To achieve comparable morphological cathode layer qualities, Dynamic Light Scattering (DLS) helped optimize the average agglomerated particle size and ink suspension stability. First, the catalyst ink was diluted using isopropanol for a constant initial transmittance (~20%; NiNC-IMI 600 times; NiNC-PANI: 60 times), and each test lasted 40 mins. The diluted NiNC-IMI catalyst ink suspension showed high stability in our test. Its hydrodynamic radius stayed around 260 nm with constant transmittance. On the contrary, the radius of NiNC-PANI dropped from 900 nm to 500 nm during this period, and the suspension turned transparent due to faster particle precipitation (Supplementary Figure ). These insights prompted adjustments in our ink deposition protocols to ensure comparable layer qualities.