# Local Variations in Current Density and Selectivity in CO2 Electrolyzers

## TL;DR

This paper studies how CO2 electrolysis performance varies across different parts of a reactor, showing the need to monitor local conditions for efficient scaling.

## Contribution

The study introduces a zero-gap flow cell that enables localized monitoring of CO2 electrolysis performance.

## Key findings

- Localized monitoring reveals spatial inhomogeneities in selectivity and current density.
- Parasitic hydrogen evolution is identified under specific operating conditions.
- Operating parameters significantly influence local product formation and current density profiles.

## Abstract

As CO2 electrolysis emerges as a key technology
for
industrial decarbonization, scaling from lab to industrial systems
introduces challenges beyond increasing the active area or the CO2 feed rate. Larger reactors often exhibit spatial inhomogeneities
in selectivity and current density, issues overlooked in conventional
performance studies. To address this, we designed, built, and tested
a zero-gap flow cell for CO2 electrolysis that enables
local monitoring of the product selectivity and current density. Gas
composition is sampled at multiple points along the flow path, while
current density is tracked across the cell. This approach reveals
where and under what conditions parasitic hydrogen evolution occurs.
In this work we present how operating parameters influence localized
product formation and current density profiles in a CO2-to-CO electrolyzer. Our findings emphasize the importance of moving
beyond averaged metrics to achieve efficient, uniform operation across
the cell, an essential step for successful scale-up.