We first consider the electrochemical response of a Cu foil in 0.1 M NaxH3-xPO4 in the With the addition of 0.1 M NaNO3, the onset of NO3RR becomes apparent at ca. 0 VRHE, with a mass-transfer limited peak evident by ca. -0.25 VRHE (Figure ). Current increases further under increasingly cathodic potentials, with water dissociation evident by -0.7 VRHE, coincident with observable bubble formation. The peak current density corresponding to the mass-transfer limited wave (jPeak, ca. -0.25 VRHE) decreases with increasingly cathodic sweep bounds (Figure ). For the least-cathodic sweep bounds capable of achieving mass-transfer limitations (-0.3 VRHE), jPeak is comparable to that observed for phosphate deprotonation in the absence of nitrate (ca. -1.6 mA/cm 2 ECSA). However, as CV sweep bounds are made increasingly cathodic, jPeak decreases in magnitude to ca. -1.1 mA/cm 2 ECSA for CV sweep -