State Key Joint Laboratory of Environment Simulation and Pollution Control, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China.
Center for Excellence in Regional Atmospheric Environment, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China.
Environ Sci Technol. 2022 Mar 15;56(6):3710-3718. doi: 10.1021/acs.est.1c07739. Epub 2022 Feb 23.
Selective catalytic reduction of NO by ammonia (NH-SCR) on VO/TiO catalysts is a widely used commercial technology in power plants and diesel vehicles due to its high elimination efficiency for NO removal. However, the mechanistic aspects of the NH-SCR reaction, especially the active sites on the VO/TiO catalysts, are still a puzzle. Herein, using combined operando spectroscopy and density functional theory calculations, we found that the reactivity of the Lewis acid site was significantly overestimated due to its conversion to the Brønsted acid site. Such interconversion makes it challenging to measure the intrinsic reactivity of different acid sites accurately. In contrast, the abundant V-OH Brønsted acid sites govern the overall NO reduction rate in realistic exhaust containing water vapor. Moreover, the vanadia species cycle between V═O and V-OH during NO reduction, and the re-oxidation of V species to form V is the rate-determining step.
在电站和柴油车中，氨（NH-SCR）选择性催化还原 NO（NO 通过氨选择性催化还原）是一种广泛应用的商业技术，因为它对去除 NO 具有很高的去除效率。然而，NH-SCR 反应的机理方面，特别是 VO/TiO 催化剂上的活性位，仍然是一个谜。在此，我们通过结合原位光谱和密度泛函理论计算，发现由于Lewis 酸位转化为 Brønsted 酸位，Lewis 酸位的反应性被严重高估。这种相互转化使得准确测量不同酸位的固有反应性变得具有挑战性。相比之下，在含有水蒸气的实际废气中，丰富的 V-OH Brønsted 酸位控制着整体的 NO 还原速率。此外，在 NO 还原过程中，氧化钒物种在 V═O 和 V-OH 之间循环，而 V 物种的再氧化形成 V 则是速率决定步骤。
