For the most commonly-used set of materials, access to >200 mA/cm 2 current densities can then provide a secondary means of suppressing hydrogen evolution by weakening hydrogen binding energies under higher local pH conditions. A secondary, non-material approach for suppressing hydrogen is particularly important for multi-carbon product formation where, despite achieving 100-fold C2:C1 ratios, many of the best catalysts when operated in an Hcell are constantly dogged by a persistent 20-30% H2 selectivity. When these same catalyst are operated under elevated current densities in the configurations and electrolytes described here (Fig. and), the selectivity towards target products could be increased purely by penalizing hydrogen evolution, rather than necessarily promoting CO2 reduction activity.