The regulation of electron transfer is crucial for enhancing the catalytic efficiency of catalysts. Currently, CO selective reduction of NOx (CO-SCR) catalysts with surface synergistic oxygen vacancies (SSOVs) or alloyed components exhibit superior performance but face challenges of reduced activity and stability in oxygen-rich environments. Here, we demonstrate a strategy that combines PtCo alloys (0.01% Pt; 0.04% Co) with SSOVs in cerium zirconium oxide solid solution to interactively modulate the electronic structure, resulting in a significant enhancement of both the activity and stability of the catalyst under oxygen-rich conditions. This catalyst achieved over 85% NO conversion at 300 °C and 5% O2, while maintaining approximately 100% N2 selectivity during 20 h-stability testing, surpassing the performance of the monometallic catalysts. This enhancement arises from the synergistic electronic effects of alloying and SSOVs, which generate negatively charged Pt that facilitates NO adsorption and dissociation, while concurrently producing electron-deficient SSOVs that weaken O2 chemisorption and promote the formation of moderate reactive oxygen species. Moreover, the preferential adsorption of CO on Co sites alleviates competitive adsorption.
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Generating different types of defects in heterogeneous catalysts for synergetic promotion of the reactivity and selectivity in catalytic reactions is highly challenging due to the lack of effective theoretical guidance. Herein, we demonstrate a facile strategy to introduce two types of defects into the CuO-ZnO model catalyst, namely oxygen vacancies (OVs) induced by H2 partial reduction and localized amorphous regions (LARs) generated via the ball milling process. Using industrially important Rochow–Müller reaction as a representative, we found OVs predominantly improved the target product selectivity of dimethyldichlorosilane, while LARs significantly increased the conversion of reactant Si. The CuO-ZnO catalyst with optimized OVs and LARs contents achieved the best catalytic property. Theoretical calculation further revealed that LARs promote the generation of the Cu3Si active phase, and OVs impact the electronic structure of the Cu3Si active phase. This work provides a new understanding of the roles of different catalyst defects and a feasible way of engineering the catalyst structure for better catalytic performances.
Mn-based catalysts have exhibited promising performance in low-temperature selective catalytic reduction of NOx with NH3 (NH3-SCR). However, challenges such as H2O- or SO2-induced poisoning to these catalysts still remain. Herein, we report an efficient strategy to prepare the dual single-atom Ce-Ti/MnO2 catalyst via ball-milling and calcination processes to address these issues. Ce-Ti/MnO2 showed better catalytic performance with a higher NO conversion and enhanced H2O- and SO2-resistance at a low-temperature window (100−150 °C) than the MnO2, single-atom Ce/MnO2, and Ti/MnO2 catalysts. The in situ infrared Fourier transform spectroscopy analysis confirmed there is no competitive adsorption between NOx and H2O over the Ce-Ti/MnO2 catalyst. The calculation results showed that the synergistic interaction of the neighboring Ce-Ti dual atoms as sacrificial sites weakens the ability of the active Mn sites for binding SO2 and H2O but enhances their binding to NH3. The insight obtained in this work deepens the understanding of catalysis for NH3-SCR. The synthesis strategy developed in this work is easily scaled up to commercialization and applicable to preparing other MnO2-based single-atom catalysts.
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