With increasing nitrate concentration, current density corresponding to nitrate reduction (potentials less cathodic than -0.35 VRHE) becomes increasingly apparent (Figure ). The logarithmic magnitude of the mass-transfer limited current density increases linearly with increasing logarithmic nitrate concentration (Figure ), as expected from the Randles-Sevcik and Butler-Volmer equations. Similarly, the potential at which jPeak occurs shifts to less cathodic potentials, trending linearly with increasing logarithmic nitrate concentration (Figure ). Onset potential for NO3RR (Figure , interpolated from Figure ) becomes less cathodic with increasing logarithmic nitrate concentration where this nominally linear trend is expected from the Nernst equation from a shift in the equilibrium potential.