Stability enhancement of CeO2/MnOx via hydrophobic modification for NO reduction by NH3

CeO2/MnOx catalysts for low-temperature selective catalytic reduction (SCR) of NO remain vulnerable to water and sulfur poisoning, limiting their practical applications. Here, we report a hydrophobic-modified CeO2/MnOx catalyst that achieves enhanced NO conversion rate and stability under harsh conditions. The catalyst was synthesized by decorating MnOx crystals with amorphous CeO2, followed by loading hydrophobic silica on external surfaces. The hydrophobic silica allowed adsorption of NH3, NO and diffusion of H, suppressed the adsorption of H2O, and prevented SO2 interaction with Mn active sites, achieving selective molecular discrimination at the catalyst surface. At 120 °C, under H2O and SO2 exposure, the optimal hydrophobic catalyst maintains 82% NO conversion rate compared to 69% for the unmodified catalyst. Average adsorption energy of NH3, H2O and SO2 decreased by 0.04, 0.43, and 0.52 eV, respectively. The NO reduction pathway follows the Eley-Rideal mechanism, NH3* + * → NH2* + H* followed by NH2* + NO* → N2* + H2O*, with NH3 dehydrogenation being the rate determining step. Hydrophobic modification was found to increase the activation energy for H atom transfer, which led to a minor decrease in NO conversion rate at 120 °C (94% vs 99%). This work demonstrates a viable strategy for developing robust NH3-SCR catalysts capable of operating efficiently in water- and sulfur-rich environments.