Atomic layer deposition of ZnO gas diffusion electrodes for tunable CO2 electroreduction in membrane electrode assemblies

The electrochemical conversion of CO2 to CO in membrane electrode assembly (MEA) electrolyzers using gas diffusion electrodes (GDEs) offers a sustainable and scalable pathway for carbon utilization. Here, we present a one-step atomic layer deposition (ALD) approach to prepare ZnO-based GDEs with tunable loadings and high selectivity toward CO. Increasing the number of ALD cycles raises the ZnO loading but progressively reduces the pore accessibility within the GDE. An optimal balance is achieved at 200 ALD cycles, delivering a peak CO faradaic efficiency (FECO) of 88% and a full-cell energy efficiency of 38% at -100 mA cm-2. Crucially, the scalability of ALD is demonstrated through stable long-term testing, achieving 85% FECO in a 5 cm2 MEA after 30 h, and 80% FECO in a 100 cm2 MEA after 24 h. These results establish ALD as an effective and versatile strategy for fabricating high-performance ZnO electrodes for CO2 electrolysis.