PhD Thesis Defence Presentations - Theocharis Kentri

Amidst escalating environmental crises of the 21st century, global attention has increasingly turned to the human impact on the planet, spurring actions from both organizations and governments. The challenges posed by soaring energy demands and the resulting environmental pollutants, largely driven by rapid industrialization and population growth, underscore the urgent need for sustainable development. Initiatives such as the UN's Sustainable Development Goals and the EU's Environmental Action Plan highlight the necessity of living within the Earth's ecological limits. In response, scientific research increasingly focuses on environmental catalysis as a key strategy to combat climate change.

Heterogeneous catalysis, which plays a pivotal role in approximately 80% of industrial processes, is crucial in the shift towards cleaner technologies. The above strategy involves shifting from traditional empirical methodologies in catalyst design and testing towards a systematic, molecular-level comprehension of catalytic phenomena, aiming for a knowledge-based design of catalytic systems. This research specifically examines (MoO_x)_n, (WO_x)_n, (VO_x)_n catalysts supported on TiO₂ carriers of different morphologies, such as TiO₂-anatase and TiO₂-Degussa P25. Despite the extensive research on these catalytic systems, there remain unanswered questions regarding their site configurations, coordination environment, site reactivity, the role of retained surface water, the role of support-dispersed phase interactions, and the factors influencing dispersed species sites speciation, dominance, and (MO_x)_n  (M=W, Mo, V) domain growth patterns.

The study advocates for a knowledge-driven approach to catalyst design, employing advanced synthesis methods to achieve a well-dispersed oxo-metallic phase on TiO₂, along with in situ Raman and FTIR spectroscopy, neoteric static Raman experiments, and isotopic labeling techniques. By conducting a comprehensive investigation considering temperature, coverage, and dehydration level under oxidative dehydrated conditions, the research seeks to uncover the structural characteristics and atomic-scale rearrangements of these catalysts. Additionally, the study explores the potential to fine-tune the dispersed phase of catalysts after calcination to control their selectivity, efficiency, and industrial relevance. Finally, by testing selected VOx/TiO₂ catalysts under NH₃-SCR conditions, the research aims to gain fundamental structural insights, ultimately contributing to a deeper understanding of molecular-level mechanistic aspects involved in this process.