De-Poisoning Catalysts for Sustainable Chemical Processing

Metal catalyst enabled chemical processing produces the majority of products that we use in everyday life, from food, textiles, biodegradable plastics, pharmaceuticals, to environmentally safer fuels. Catalyst poisoning not only reduces the efficiency of these catalysts but also increases the demand for them. De-poisoning catalysts can not only improve the efficiency and sustainability of chemical processing but also address the lesser known yet serious fact that many catalysts are sourced from minerals mined in countries struggling with political instability, where the extraction of minerals is linked to environmental damage, violence, and human rights abuses.<br/><br/>Atomic layer etching (ALE) was developed in recent years to enable precision in patterning for integrating novel metal and metal alloys in nano-electronics, nano-photonics, spintronics, and sensors. Interestingly, many of the materials requiring nano-scale patterning have been used as catalysts. While a chemical reaction leading to the formation of a strongly chemisorbed species is considered poisoning in catalysis, it is a necessary step in initiating atomic layer etching of metals. The feasibility of utilizing ALE to reactivate catalysts relies on selective surface chemical reactions to remove just the poisoned layer. This presentation will focus on the intersection of two interdisciplinary research areas for nano-electronics and catalysis, leveraging what was achieved in ALE of metals to help de-poison/regenerate the catalysts. The specific example focuses on using Cu as a catalyst for CO₂ reduction, where sulfur and carbon (coking) poisoning through the use of model compounds served to deactivate the catalyst. Different plasma chemistries (e.g., Ar, O₂, N₂) are evaluated to assess the physical and chemical effects of the discharge on modifying the surface morphology, microstructure and composition. The Faradaic efficiency in the formation of main gases and liquid products (e.g., CH₄, formate, ethanol) is used to assess the efficacy of the plasma enhanced ALE processes in de-poisoning catalysts. The results demonstrated the feasibility of utilizing ALE to remedy catalyst poisoning, highlighting the effect of surface microstructure on catalytic selectivity, thereby making the catalytic processing more sustainable and effective.