Sustainable Mechanochemistry for Energy and Environment

Abstract

This thesis presents sustainable mechanochemical approaches to address both energy and environmental challenges. The first subject focuses on the mechanochemical decomposition of nitrous oxide (N2O) using a ball-milling process. The reaction achieved nearly 100% conversion at 42 °C, which is about five times faster in decomposition rate than the conventional thermochemical method. Structural and electronic analyses revealed that highly defective and ultra-oxidized NiO catalysts formed during milling accelerate both dissociative adsorption of N2O and O2 desorption. Practical studies demonstrated the strong potential of mechanochemical N2O decomposition in scalability, continuous process and real-world application for efficient alternative to conventional N2O decomposition. In summary, mechanochemical N2O decomposition demonstrated superior energy and cost efficiency (291 mmol∙kWh−1, 134 mmol∙$−1), thereby contributing to the mitigation of the critical greenhouse gas. The second subject investigates the mechanochemical ammonia–silicon (MAS) reaction for separation-free hydrogen production while upcycling waste silicon from discarded solar panels. The reaction achieved 100% ammonia conversion and 100% hydrogen purity within 24 minutes under mild conditions. Techno-economic analysis confirmed that this process is cost- effective, with a hydrogen production cost of $−7.14 gH2 −1 when including the value of the Si3N4 byproduct. In conclusion, the mechanochemical NH3–Si reaction enabled a cost-efficient process to produce high purity H2 and environmentally upcycled waste solar panels. Overall, this thesis demonstrates that mechanochemistry is a sustainable strategy for solving energy and environmental problems simultaneously.