posted on 2023-11-09, 13:08authored byDong Un Lee, Bjørt Joensen, Joel Jenny, Victoria M. Ehlinger, Sang-Won Lee, Kabir Abiose, Yi Xu, Amitava Sarkar, Tiras Y. Lin, Christopher Hahn, Thomas F. Jaramillo
The development of high-performance
CO2 electrolyzers
is crucial for accelerating the sustainable production of fuels and
chemicals integrated with renewable energy sources. Here, we introduce
a methodology to actively control mass transport inside a realistic
zero-gap membrane electrode assembly of a CO2 electrolyzer
by varying the gasket thickness, which consequently changes the cell
compression. This allows control over the thickness and porosity of
the gas diffusion electrodes, influencing the overall electrolyzer
performance, as demonstrated using Ag-deposited electrodes. At low
operating voltages (<2.9 V), both high- and low-compression electrolyzers
exhibit similar faradaic efficiencies and partial current densities
for CO formation. However, at high voltages, the low-compression electrolyzer
with high electrode porosity demonstrates superior CO selectivity
and activity with suppressed H2 formation. These experimental
results are validated by the computational membrane electrode assembly
(MEA) model developed by using the measured in situ electrode thicknesses
and electrode porosities. Additionally, liquid electrolyte saturation
at the catalyst layer is found to play a dominant role in determining
the mass transport, resulting in a decreased electrolyzer performance
with low electrode porosity. The systematic investigation in this
study improves the understanding of the transport dynamics in MEA-based
devices and provides insights into optimizing device design parameters
for industry-relevant CO2 electrolysis.