Ho‑doping enhanced CuO/CeO2 nanorods for low‑temperature synergistic NH3‑SCR and CO oxidation under oxygen‑rich conditions

Although the simultaneous removal of NOₓ and CO from industrial flue gas has been extensively studied, existing catalysts still perform poorly under low-temperature, oxygen-rich conditions. This research synthesized a range of holmium (Ho)-modified CuO/CeO 2 nanorod catalysts via a hydrothermal and subsequent co-impregnation method, demonstrating excellent catalytic efficiency for NO x reduction and CO oxidation at low temperatures. Under conditions with 10 % O 2 , the catalysts achieved approximately 90 % NO x and near-complete CO conversion. Structural analyses indicated that introducing Ho into the CeO 2 nanorods reduced surface pore sizes without altering the fundamental catalyst framework. Additionally, Ho incorporation notably increased the levels of Ce 3 + , Cu + , and chemisorbed oxygen species, enhancing interactions between Cu and Ce. These changes significantly improved electron mobility, thereby enhancing the redox properties of the catalysts. Further characterization by NH 3 -TPD and in-situ infrared spectroscopy confirmed an increase in Brønsted acid site density due to Ho doping, substantially enhancing the reactivity of adsorbed NH 3 . In-situ infrared spectroscopy revealed surface bidentate nitrates (bid-NO 3 - ) and bidentate carbonates (bid-CO 3 2- ), while NH 3 -SCR is likely governed by a Langmuir–Hinshelwood pathway and CO oxidation follows a Mars–van Krevelen mechanism. Overall, this work offers valuable guidance for developing efficient catalytic systems to concurrently reduce CO and NO x emissions in oxygen-rich industrial environments. • Ho-modified CuO/CeO 2 achieves 100 % CO and 90 % NO x conversion at 150–200 °C. • Ho elevates Ce 3+ /Ce 4+ , Cu⁺/Cu 2 ⁺ and O α , created vacancies and rapid charge transfer. • Ho strengthens Brønsted acidity, enhancing NH 3 adsorption/dissociation. • Low-temperature L‑H SCR and M‑v‑K CO cycles accelerate under Ho doping.