Danae A. Chipoco Haro
Advisor: Prof. Marta C. Hatzell. Co-advisor: Prof. Faisal M. Alamgir
will propose a doctoral thesis entitled,
Designing catalysts for electrochemical conversion of waste to value-added products
On
Monday, August 31 at 2:30 p.m.
MRDC Room 3515
Committee
Prof. Marta C. Hatzell – School of Chemical and Biomolecular Engineering, George W. Woodruff School of Mechanical Engineering (advisor)
Prof. Faisal M. Alamgir– School of Materials Science and Engineering (co-advisor)
Prof. Guoxiang (Emma) Hu – School of Materials Science and Engineering
Prof. Preet M. Singh – School of Materials Science and Engineering
Dr. Shawn M. Dirk – Sandia National Laboratories
Abstract
Nitrogen- and carbon-containing species circulate through Earth's ecosystems and play essential roles in sustaining life. Nitrogen is a crucial nutrient, while carbon regulates the climate on Earth. However, anthropogenic activities have disrupted these natural cycles, among other factors, through the widespread application of fertilizers and the extensive use of fossil fuels. As a consequence, water bodies are poisoned due to an increase in nutrient concentration. The chemical industry has disrupted the nitrogen and carbon cycle, which is exemplified by the Haber-Bosch process. The Haber-Bosch process synthesizes ammonia, a key chemical in fertilizer production that relies on fossil-derived feedstocks. The excess of nutrients in fertilizers results in a high nitrogen concentration in wastewater, specifically as nitrate. Wastewater treatment plants process wastewater into sludge, but do not transform the sludge into value-added products. The nitrogen that persists in the sludge after treatment (or digestion) is usually in the form of glycine. The present thesis proposes the synthesis of ammonia through the electrochemical conversion of waste, nitrate and glycine, as a strategy to replace fossil-derived resources with waste-derived feedstocks, thereby contributing to the restoration of a more sustainable and circular nitrogen and carbon cycle.
Nitrate reduction and glycine oxidation may yield several products in addition to ammonia. Thus, achieving an efficient electrochemical conversion of these waste streams requires a fundamental understanding of the reaction mechanisms and rational catalyst design to precisely control the reaction selectivity to ammonia. Regarding nitrate reduction, transition metal hydrides are hypothesized to enhance ammonia selectivity by increasing hydrogen availability at the catalyst surface. However, the role of interstitial hydrogen incorporated within metal lattices remains largely unexplored. However, the role of interstitial hydrogen incorporated within metal lattices remains largely unexplored. This study aims to advance the understanding of interstitial metal hydride catalysts and their potential in catalytic applications. Glycine oxidation can proceed through either C–C or C–N bond cleavage, producing predominantly C₁ or C₂ products, respectively. The factors that govern the competition between these pathways on transition metal surfaces remain poorly understood. Therefore, this work will elucidate the reaction pathway of glycine oxidation on nickel, identify key reaction intermediates associated with C₂ product formation, and evaluate the influence of reaction conditions on C–C and C–N bond cleavage. Overall, this thesis seeks to establish catalyst design principles for the electrochemical conversion of nitrogen-containing waste streams into value-added products, contributing to the remediation of nitrogen and carbon cycles.