Houston Daily

In a collaborative effort, scientists from the University of Houston and Rice University have developed a solution to a significant problem affecting carbon capture and utilization technology, specifically the carbon dioxide reduction reaction (CO 2RR). This research, led by Xiaonan Shan, associate professor at the University of Houston, and Haotian Wang, associate professor at Rice University, was recently published in Nature Energy.

The CO 2RR process, which uses electricity and chemical catalysts to turn carbon dioxide into useful carbon compounds, faces a major hurdle due to salt build-up. This salt formation impairs the flow of reactant gases and can eventually lead to reactor damage. Shan commented on the significance of these advancements, stating, “This advancement paves the way for longer-lasting and more reliable CO 2RR systems, making the technology more practical for large-scale chemical manufacturing.”

Over time, bicarbonate salt crystals form in commercial membrane electrode assembly electrolyzers, which hinders the flow of carbon dioxide gas, affecting the device's performance and leading to failure. Wang noted, “Operational instability is a big hurdle in the wider adoption of this technology — the device functions normally for a few hundred hours after which it stops working due to the buildup of salt.”

To address this, Shan and Wang investigated how these salts form within the devices. Shan explained, “Salt accumulation is problematic because it leads to the formation of bicarbonate salt particles... These precipitates block CO 2 diffusion pathways...” The team utilized operando Raman spectroscopy, which allowed them to study salt formation as it happens.

The solution involved lowering the concentration of cations like sodium and potassium, which slowed salt formation. This approach improved the reactor’s long-term stability. Wang observed: “As we visualized this reaction using optical microscopy, we saw an interesting phenomenon. The bicarbonate crystals formed and remained trapped in droplets initially...”

Inspired by natural phenomena, they also tested coating the gas flow channels with a water-repelling polymer, which reduced salt build-up. “...we wondered if coating the gas flow channel with a non-stick substance will prevent salt-laden droplets from staying on the surface of the electrodes for too long...” Wang explained. This method notably improved the stability and functional life of the CO 2RR MEA electrolyzer.

Wang expressed optimism about the potential impact of their solutions: “...we believe that the easy scalability of these solutions to commercial applications will drive wider adoption of CO 2RR technology as a means to manufacture chemicals and combat climate change.”

The research was funded by various foundations and institutions, including the Robert A. Welch Foundation, the David and Lucile Packard Foundation, and others.