High-Resolution Neutron Imaging of Water Transport in CO2 Electrolysis during Pulsed Operation

Abstract

Low-temperature CO₂ electrolysis is a promising approach for defossilizing the production of commodity chemicals. However, state-of-the-art electrolyzers often suffer from low stability due to salt precipitation and electrode flooding. One strategy to increase the stability is pulsed operation of the electrolyzer, i.e. repeated application of low potentials (resting period). However, the water management of this operation mode is poorly understood. This work presents the first quantitative operando analysis of the water management in a CO₂ electrolyzer under application relevant operation conditions via high-resolution neutron imaging (<6 μm). Within 100 h of operation at 400 mA cm^–2, pulsed operation shows a significant stabilization of voltage and selectivity (1.8 mV h^–1 and −0.002% h^–1) compared to constant current operation (2.9 mV h^–1 and −0.11% h^–1). During the resting period, pulsed operation introduces 2.2 μL cm^–2 of additional water to the cathode, which facilitates the removal of salt precipitates and mitigates uncontrolled electrode flooding.