No abstract

Under oxygen‐rich conditions, achieving a selective and efficient reduction of NO by CO is always challenging. Here, we report the synthesis of the catalyst consisting of single Ir atoms anchored on mesoporous WO3 (denoted as Ir1/m‐WO3) using a facile template method followed by wet impregnation. X‐ray diffraction and transmission electron microscope studies indicated that the Ir atoms were distributed uniformly on the internal surface of m‐WO3. When tested for the reduction of NO by CO, the Ir1/m‐WO3 catalyst with a low Ir loading of 0.28 wt % exhibited excellent catalytic performance in the presence of 2 vol % O2 (volume ratio of CO to O2 being 1 : 10), achieving a NO conversion of 73 % and N2 selectivity of 100 % at 350 °C. In particular, its turnover frequency (TOF) value reached 0.30 s−1 at 200 °C, which is six times higher than that of the catalyst with Ir nanoparticles supported on mesoporous WO3 (0.05 s−1). The superior catalytic performance of Ir1/m‐WO3 is attributed to the formation of the isolated Ir atoms and the more newly generated Ir‐WO3 interfaces that can promote the adsorption and activation of NO, and the presence of accessible mesopores in m‐WO3 that facilitates the mass transfer of NO and CO. This study brings a new fundamental understanding of active sites in Ir‐based catalysts for the CO+NO reaction and provides a new way to the design and synthesis of single‐atom catalysts, especially precious metal catalysts for emissions control.

CO selective catalytic reduction (CO‐SCR), a promising technology for simultaneous removal of harmful CO and NO in exhaust gases, has attracted much attention in recent years. Pt‐based catalysts have been demonstrated to be effective for this reaction. However, it remains a big challenge to achieve a high low‐temperature activity at a low Pt loading. Here we report a new catalyst consisting of subnanometric Pt on Cu nanoparticles confined in the NaOH‐modified Y‐zeolite (Pt−Cu@M−Y). This catalyst possesses enhanced catalytic performance in CO‐SCR at an extremely low Pt content of 0.04 wt %, achieving full NO conversion at 250 °C. The Pt−Cu@M−Y catalyst was synthesized using a simple impregnation method followed by a hydrogen reduction. Transmission electron microscopy study revealed that Pt−Cu@M−Y with subnanometric Pt on Cu nanoparticle of ∼5 nm was highly dispersed in M−Y. The superior catalytic property of Pt−Cu@M−Y is attributed to the synergistic catalysis of Pt and Cu, in which subnanometric Pt species contributes to the strong adsorption of NO, while the dissociation of NO and the migration of dissociated O atoms are significantly boosted on the newly generated interfaces between Cu nanoparticles and the formed surface CuOx species. This work develops an effective method for synthesizing bimetallic nanoparticles confined in zeolite and demonstrates their superior catalytic performance in the catalytic reduction of NOx by CO.