High-resolution neutron imaging of carbonate precipitation and water transport in zero-gap CO2 electrolysis

Abstract

The electrochemical reduction of CO2 is a pivotal technology for the defossilization of the chemical industry. Although first pilot-scale electrolyzers exist, water management and salt precipitation remain a major hurdle to long-term operation. In this work, we present the first high resolution neutron imaging (6 µm) of a zero-gap CO2 electrolyzer to uncover water distribution and salt precipitation under application-relevant operating conditions (200 mA cm− 2 at 2.8 V with a Faraday efficiency for CO of 99%). Precipitated salts penetrating the cathode gas diffusion layer can be observed, which are believed to block the CO2 gas transport and are therefore the major cause for the commonly observed decay in Faraday efficiency. Neutron imaging further shows higher carbonate accumulation under the cathode channel of the flow field compared to the land. In fact, a higher local reaction rate under the land compared to the channel can be estimated from the gas bubble generation on the opposing anode side.

Anion-exchange membranes with internal microchannels for water control in CO2 electrolysis

“…17,36 Additionally, work by Disch et al has used neutron-imaging to experimentally demonstrate that the loss of water content is prevalent in Ag-AEMEAs performing the reduction of CO 2 to CO, and the simulated water content profiles for the no-channel case are consistent with the trends shown experimentally, wherein upon increases in current density, the water content near the membrane-GDE interface is substantially reduced. 37 Interestingly, the average water content at the CL at a given applied potential is reduced at lower channel spacings, particularly around the channels themselves (Figure 4b-c). This behavior can be rationalized as follows.…”

Towards in-situ water quantification via neutron imaging: insights from NeXT-Grenoble

“…These properties have rendered neutron imaging an attractive tool applicable to a wide array of scientific disciplines, spanning from materials science to biology, archaeology, and geology [2,7,8]. Notably, the measurement of hydrogen distribution, particularly water, holds significant interest and is relevant for many domains, ranging from fuel cells [9], electrolyzer [10], food industry [11], concrete and cement science [12,13], wood and plant research [4,14], fabrics [15], as well as studies of multiphase transport in porous media [16,17], to mention only a few.…”