Phosphorus (P) originating from lubricant oil additives or biofuels is an emerging chemical poison in catalytic systems for automotive exhaust after-treatment. Here, we demonstrate that P-poisoning led to severe deactivation of small-pore Pd-SSZ-13 zeolites (with CHA framework) as passive NO x adsorbers (PNA) and CO oxidation catalysts for cold-start exhaust purification applications. Deactivation mechanisms of P-poisoning were unraveled by comparatively examining the P-free and P-loaded Pd-SSZ-13 zeolites using transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), nuclear magnetic resonance (NMR), temperature-programmed reduction by hydrogen (H2-TPR), CO pulse adsorption, temperature-programmed desorption using NH3 as a probe molecule (NH3-TPD), ultraviolet/visible light (UV/vis) spectroscopy, and in situ diffuse relectance infrared Fourier transform spectroscopy (DRIFTS). The loss of isolated Pd sitesnamely, [Pd­(OH)]+ and Pd2+ (located in the eight- and six-membered rings of CHA framework, respectively)was revealed to be largely responsible for the deactivation of Pd-SSZ-13 in passive NO x adsorption and catalytic CO oxidation. In situ DRIFTS studies using NO or CO as a probe molecule suggest that [Pd­(OH)]+ was more susceptible to P-poisoning than Pd2+. Specifically, P-poisoning led to a migration of [Pd­(OH)]+ from cationic exchange sites to the zeolite surface, forming inactive metaphosphate (i.e., [Pd­(OH)]+PO3 –) and bulk PdO x species at high temperatures. In contrast, P-poisoning of Pd2+ sites proceeded via a sequential transformation to [Pd­(OH)]+ first, and then to [Pd­(OH)]+PO3 – and bulk PdO x . This study provides a comprehensive mechanistic understanding on the deactivation of Pd-SSZ-13 by P-poisoning, and may guide the design of high-performance, phosphorus-resistant Pd-zeolite catalysts for cold-start exhaust after-treatment.

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Bi2MoO6 quantum dots (BM QDs, 5 nm in diameter) are evenly in situ grown on reduced graphene oxide (rGO) layers, sensitizing the graphene with high visible light response and activity for efficient solar light-driven CO2 reduction. Under irradiation, small-sized BM QDs generate active electrons and donate them to the rGO layers. Since the formation of BM QDs and the reduction of GO are undergone simultaneously, a close connection between BM QDs and rGO enables the electron injection from excited Bi2MoO6 QDs to graphene scaffolds, and abundant electrons accommodated by the rGO layers offer an electron-rich interface for CO2 reduction. With the benefit of the improved electron extraction and transport over the BM QDs/rGO interface, 84.8 μmol g–1 of methanol and 57.5 μmol g–1 of ethanol are achieved on BM QDs/rGO in 4 h with optimal composition. The total output of alcohols over BM/rGO (142.3 μmol g–1) is 2.2 and 4.4 times that achieved on unmodified Bi2MoO6 QDs (64.0 μmol g–1) and flower-like Bi2MoO6 (32.2 μmol g–1), respectively.

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The application of small-pore chabazite-type SSZ-13 zeolites, key materials for the reduction of nitrogen oxides (NO x ) in automotive exhausts and the selective conversion of methane, is limited by the use of expensive N,N,N-trimethyl-1ammonium adamantine hydroxide (TMAdaOH) as an organic structure-directing agent (OSDA) during hydrothermal synthesis. Here, we report an economical and sustainable route for SSZ-13 synthesis by recycling and reusing the OSDA-containing waste liquids. The TMAdaOH concentration in waste liquids, determined by a bromocresol green colorimetric method, was found to be a key factor for SSZ-13 crystallization. The SSZ-13 zeolite synthesized under optimized conditions demonstrates similar physicochemical properties (surface area, porosity, crystallinity, Si/Al ratio, etc.) as that of the conventional synthetic approach. We then used the waste liquid-derived SSZ-13 as the parent zeolite to synthesize Cu ion-exchanged SSZ-13 (i.e., Cu-SSZ-13) for ammonia-mediated selective catalytic reduction of NO x (NH 3 -SCR) and observed a higher activity as well as better hydrothermal stability than Cu-SSZ-13 by conventional synthesis. In situ infrared and ultraviolet−visible spectroscopy investigations revealed that the superior NH 3 -SCR performance of waste liquid-derived Cu-SSZ-13 results from a higher density of Cu 2+ sites coordinated to paired Al centers on the zeolite framework. The technoeconomic analysis highlights that recycling OSDA-containing waste liquids could reduce the raw material cost of SSZ-13 synthesis by 49.4% (mainly because of the higher utilization efficiency of TMAdaOH) and, meanwhile, the discharging of wastewater by 45.7%.