Pulsed electrolysis through neutron lenses

Abstract

Now, Joey Disch and colleagues study eCO2R under operando conditions using high-resolution neutron radiography, focusing on water transport and distribution within a zero-gap membrane electrode assembly with an AEM. The cell, with a silver cathode catalyst for CO production, is operated at both constant current and pulsed electrolysis under either 34% or 100% relative humidity (RH), in 0.1 M KHCO₃ electrolyte, at 50 °C and at a current density of 400 mA cm^–2, except for the brief pulses — 1 minute after every 10 minutes of operation — at open-circuit voltage (OCV).

As expected, pulsed electrolysis exhibits higher stability than at constant current in terms of both voltage and Faradaic efficiency (FE) for CO. Neutron radiography reveals that during the brief periods at OCV the amount of water at the cathode increases, especially at higher RH, which allows the dissolution of carbonate precipitates, preventing accumulation. However, while high FE for CO is continuously achieved at lower RH, CO₂ transport gets limited under 100% RH due to the increase in water content. On the other hand, multiple flooding events are observed at constant current, especially under high humidification. Water management is further improved in 0.01 M Cs₂CO₃ electrolyte, and the researchers argue that focusing on optimizing both the pulse strategy parameters and the electrolyte should lead to improvements in performance, and that the strategy’s transferability to cell stacks should be explored.