For CO production, an acidic-form cathode half-reaction is CO₂ + 2 H⁺ + 2 e⁻ → CO + H₂O. A full electrolyser also needs an anode reaction, ion transport and product separation. Faradaic efficiency describes how charge is allocated to a product; it is not a direct measure of overall energy efficiency. Gas diffusion electrodes and key metrics
Read the operating point as a set
Compare selectivity together with full-cell voltage, product partial current density, electrode area, feed conversion and operating time. An attractive result from a small electrode does not establish stable operation of a large stack.
Carbonate formation, flooding, salt precipitation and component degradation can change carbon efficiency and lifetime. Membranes, supports and anodes introduce resource and replacement burdens that belong in scale-up analysis. Materials challenges for CO₂ electrolysis
Analyst reading rule: ask for the full carbon balance, outlet concentrations, separation duty and degradation trajectory. Record what was measured and what was modeled separately.