Solvent-free rapid synthesis of porous CeWOx by a mechanochemical self-assembly strategy for the abatement of NOx

Abstract

Herein, we designed and initiated a novel mechanochemical self-assembly protocol that realized a rapid and solvent-free construction of a series of highly porous CeWO_x oxides with high specific surface areas up to 143 m² g⁻¹, and their catalytic activities were examined for selective catalytic reduction of NO_x with NH₃ (NH₃-SCR). Experimental results revealed that Ce_0.8W_0.2O_x exhibited the broadest activity temperature window for NO_x abatement (210–440 °C) and excellent resistance to SO₂ and H₂O poisoning under a high gas hour space velocity (GHSV = 125 000 h⁻¹) on account of its high specific surface area, abundant acid and redox sites, as well as more exposed active sites. DFT calculations unveiled that the amount of W dopant significantly influenced the structure of active sites, and that Ce_0.8W_0.2O_x exhibited the lowest oxygen vacancy formation energy (0.84 eV) and the strongest NH₃ binding ability (−1.55 eV). Furthermore, kinetics experimental results disclosed that the incorporation of mesopores into CeWO_x induced the exposure of more active sites, thereby facilitating the access of reactants to more active sites and the adsorption and activation of ammonia species, thereafter promoting the catalytic performance of CeWO_x catalysts. Therefore, this work not only introduces a new opportunity for fabricating a number of advanced porous materials, but also provides insight into the crucial role of mesopores and dopants in heterogeneous catalysis reactions.