i is the net current density (i = ia + ia) (mA cm−2)

ia is the anodic branch current density (mA cm−2)

ia is the cathodic branch current density (mA cm−2)

ha(ia) is the anodic branch polarization resistance (kΩ cm2)

hc(ic) is the cathodic branch polarization resistance (kΩ cm2)

z is the number of electrons transferred (-)

F is the Faraday’s constant (F = 96.5 × 103 A s mol−1)

R is the gas constant (R = 8.31 J mol−1 K−1)

T is the absolute temperature (K)

$\mathsf{\delta }$ is the Nernst diffusion layer thickness (cm)

$i_{\mathrm{Cu}{(\mathrm{HCOO})}_2}$ is the limiting diffusion current density of $\mathrm{Cu}{(\mathrm{HCOO})}_2$ (mA cm−2)

${[\mathrm{Cu}{(\mathrm{HCOO})}_2]}_{\mathrm{bulk}}$ is the activity of $\mathrm{Cu}{(\mathrm{HCOO})}_2$ in the bulk solution (-)

$k_{\mathrm{Cu}{(\mathrm{HCOO})}_2,\mathrm{L}}$ is the limiting diffusion rate constant of $\mathrm{Cu}{(\mathrm{HCOO})}_2$ (cm s−1)

$D_{\mathrm{Cu}{(\mathrm{HCOO})}_2}$ is the limiting diffusion coefficient of the $\mathrm{Cu}{(\mathrm{HCOO})}_2$ (cm2 s−1)