OVI-Guided Tuning of Oxygen Vacancies in Fly Ash Denitrification Catalysts

Denitrification catalysts are essential for reducing NO_x emissions from combustion and protecting air quality. This study introduces and validates an Oxygen Vacancy Index (OVI) that quantifies redox-active vacancies and guides defect engineering in fly ash-derived catalysts. We apply a simple cascade strategy to tune defect types; procedural details are reported in Methods rather than in the abstract. The optimized catalyst shows an over-twofold increase in OVI compared with raw fly ash. Surface-related changes and point/line defects contribute comparably (≈one-third each) to the explained variance. OVI positively correlates with NO conversion, and the optimized material delivers high NO conversion at 400 °C. These results establish a quantitative process-structure-performance link. Looking ahead, the OVI framework can guide defect design in other waste-derived catalysts and support scale-up to monolith coatings and pilot-scale units. This OVI-guided route provides a simple, low-cost path to robust fly ash catalysts for industrial NO_x control.