Copper-based catalysts are among the most promising materials for the electrochemical reduction of CO₂ to multicarbon products such as ethylene; however, their performance is often limited by instability, surface restructuring, and competing reaction pathways^1,2. In this work, we investigate the use of ultrathin silica (SiO₂) layers grown by atomic layer deposition (ALD) on copper oxide nanoparticles to tune the catalyst-electrolyte interface and improve performance in a membrane electrode assembly (MEA) configuration.

Silica layers were deposited in a fixed-bed ALD reactor using a controlled number of cycles from 5 to 30 cycles. The ALD process was further optimized to reduce residual chlorine species by adjusting purge conditions, leading to improved surface quality and more reliable interfacial properties. Silica and other oxide slayers have been testing for different electrochemical reactions showing a strong permeability and selectivity for specific species without affect the electrocatalytic activity^3–5

Initial results show that ultrathin coatings (5 ALD cycles) not only preserve catalytic activity but also enhance selectivity toward ethylene. At higher current densities 200 mA/cm² , silica-modified electrodes exhibit a comparable faradaic efficiency for C₂H₄ compared to bare copper, along with a decrease in CO formation, indicating a shift in reaction pathways driven by interfacial effects. These findings suggest that the SiO₂ layer acts as a proton-permeable, semi-transparent interface that tunes the local reaction environment without blocking active sites.

Electrochemical impedance spectroscopy (EIS) was used to probe resistance changes within the MEA configuration as a function of coating thickness, providing insight into transport and interfacial phenomena. Furthermore, inductively coupled plasma (ICP) analysis revealed no detectable copper dissolution for silica-coated nanoparticles, highlighting the protective role of the ultrathin SiO₂ layer under electrolysis conditions. Complementary characterization by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) supports the structural and chemical stability of the coated systems before and after electrolysis.

Overall, this work demonstrates that ultrathin ALD-grown silica layers provide an effective strategy to enhance ethylene selectivity while improving catalyst stability, emphasizing the importance of nanoscale interface engineering in CO₂ electroreduction systems.