# How to use anodic and cathodic overpotentials to calculate electrolytic energy efficiency?

I am trying to calculate the energy efficiency for $$\ce{CO2}$$ reduction to formate, coupled to water oxidation based on literature data.

$$\ce{CO2 + 2e- + 2H+ -> HCOOH}$$ $$\ce{H2O -> 2H+ + 1/2O2 + 2e-}$$

I hope someone can help me to understand how to combine the information that is presented in the papers so I can calculate an overall energy efficiency of the reaction.

E.g. things that are given:

• cathodic overpotential
• anodic overpotential

The energy efficiency should eventually be equivalent to $$\mathrm{EE = \frac{Combustion\;energy\;of\;Formate}{Invested\;electrical\;energy}}$$

• More on the site's notation: chemistry.stackexchange.com/help/notation and chemistry.meta.stackexchange.com/q/86/73265 Mar 23 '21 at 15:26
• Note that there are additional potential differences, affecting the efficiency, that are related to non equlibrium system state due nonzero current. Like electrolyte potential gradient and electrode double layer potential shift due electrode reaction kinetics. Mar 24 '21 at 9:36