<p>The development of vanadium-free catalysts for selective catalytic reduction by ammonia (NH₃-SCR) with a broad operating temperature window and high N₂ selectivity is essential for efficient nitrogen oxide (NO_<i>x</i>) emission control. Herein, Ce/TiO₂, Ce–Sb/TiO₂, and Ce–Sb–Mo_<i>x</i>/TiO₂ catalysts were synthesized via a co-precipitation method using anatase TiO₂ as the support. The effects of Sb and Mo incorporation on NO_<i>x</i> conversion efficiency, H₂O/SO₂ resistance, and optimal Mo loading were systematically investigated. The optimized Ce–Sb–Mo_0.5/TiO₂ catalyst exhibits near-100% N₂ selectivity and a broad temperature window (250–480+ °C). Furthermore, the NH₃-SCR reaction mechanism over Ce–Sb–Mo_0.5/TiO₂ was elucidated through in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The results demonstrate that the introduction of Sb and Mo significantly enhances NH₃-SCR activity and improves the resistance to water and sulfur poisoning of the catalysts. The addition of Sb suppresses CeO₂ crystallization and promotes the uniform dispersion of Sb and Mo on the catalyst surface, while Mo incorporation enhances redox properties and increases the number of acidic sites. Mechanistic studies confirm that the NH₃-SCR reaction follows the Eley-Rideal pathway. Owing to its wide temperature window and high N₂ selectivity, the Ce–Sb–Mo_0.5/TiO₂ catalyst emerges as a promising candidate for industrial NO_<i>x</i> abatement.</p> Graphical Abstract <p></p>