Seminar: Desirée Plata, MIT

Environmental optimization enables discovery of carbon nanotube formation mechanisms

Desirée Plata, PhD

Gilbert W. Winslow Career Development Assistant Professor

Civil and Environmental Engineering

Massachusetts Institute of Technology (MIT)

Abstract: Carbon nanotubes (CNTs) are often proposed as the material solutions to environmental challenges facing society (e.g., energy storage and water treatment technologies), but their production by catalytic chemical vapor deposition (CVD) is one the least efficient industrial practices ever developed. Carbon conversion efficiencies range from 0.0001-10% and energy consumption is high compared to other industrial practices (e.g., 107 kJ/kg), even after 15+ years of optimization. Furthermore, atomic-scale control of the CNT nanostructure is not yet possible due to a lack of mechanistic understanding, and this has limited realization of many of the most promising applications of CNTs. Nevertheless, carbon-based nanomaterials remain exceptional with respect to their predicted (and demonstrated) material properties, and discovery of the bond-building steps controlling CNT formation could enable both reduction in the environmental impacts of the process, as well as improved performance of the nanomaterial-enabled devices. Using in situ CNT height measurements and complimentary gas emissions analysis of volatile organic compounds (VOCs) and polycyclic aromatic hydrocarbons (PAHs), we identified thermally generated compounds that were correlated with CNT formation rate. Direct delivery of these critical precursors (primarily C2-C4 alkynes) in a cold wall reactor to a locally-heated catalyst support enabled greater than 10-fold improvements in carbon conversion efficiency, corresponding order-of-magnitude reductions in emissions, and two-fold energetic savings.  Subsequently, we demonstrated that alkynes were responsible for rapid CNT growth and that structural elements of those persisted into the bulk CNTs. The chemical studies presented here shed new light on the current understanding of CNT synthesis, suggesting that a metal-catalyzed polymerization reaction is responsible for CNT formation.  This fundamental contribution is demonstrative of the powerful potential interactions between environmental engineers and materials scientists: where early optimization of environmental, performance, and costs metrics could enable rigorous, sustainable material design to solve global challenges.

Bio:  Desirée Plata’s research seeks to maximize technology’s benefit to society while minimizing environmental impacts in industrially important practices through the use of geochemical tools and chemical mechanistic insights, with a particular focus on energy technologies. Plata earned her doctoral degree in Chemical Oceanography and Environmental Chemistry from the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution’s Joint Program in Oceanography (2009) and her bachelors degree in Chemistry from Union College in Schenectady, NY (2003). Plata is an NSF CAREER Awardee (2016), an Odebrecht-Brasken Sustainable Innovation Awardee (2015), a National Academy of Engineers Frontiers of Engineering Fellow (2012), a two-time National Academy of Sciences Kavli Frontiers of Science Fellow (2011, 2013), and a Caltech Resnick Sustainability Fellow (2017). Having previously served as John J. Lee Assistant Professor of Chemical and Environmental Engineering at Yale University and Associate Director for Research at the Center for Green Chemistry and Green Engineering at Yale, Plata is now Gilbert W. Winslow Career Development Assistant Professor of Civil and Environmental Engineering at MIT.