Efficient Conversion of NO₂ to NO over Mo₂C/AC by Controlling Carbonization Time

Mo₂C/AC-x converters were prepared using nitric acid pretreated activated carbon (AC) as a carrier, with x representing the carbonization time. The performance of the converter in converting NO₂ to NO was evaluated in a fixed bed reactor. The Mo₂C/AC-x converters were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), N₂ physisorption and desorption, H₂ programmed temperature reduction (H₂-TPR) and NO₂ temperature-programmed desorption–mass spectrometry (NO₂ TPD-MS). The NO₂ to NO conversion rate decreases in the following order: Mo₂C/AC-4 > Mo₂C/AC-2 > Mo₂C/AC-6 > Mo₂C/AC-0.5. Short carbonization times, like 0.5 h, led to incomplete carbonization of MoO₂ to β-Mo₂C. Conversely, long carbonization times, like 6 h, resulted in the formation of carbon deposits that can block pores or cover active sites, leading to decreased catalytic performance. Mo₂C/AC-4 has the highest specific surface area and pore volume. The NO₂ conversion rate of Mo₂C/AC-4 reached 98.9% at 150°C, demonstrating direct efficient conversion of NO₂ to NO at a lower temperature.