•LaCoO3/ɤ-Al2O3/cordierite monolith catalyst was prepared by two-step method.•Alumina-washcoated catalysts presented a more uniform and more stable washcoat.•The weight loss for LaCoO3/ɤ-Al2O3/cordierite was less than 1 wt.%.•3DOM LaCoO3/ɤ-Al2O3/cordierite catalysts were prepared for the first time.•Nano LaCoO3/ɤ-Al2O3/cordierite catalyst gave the highest activity for soot combustion.The novel catalysts of LaCoO3/ɤ-Al2O3/cordierite monolith, LaCoO3/SiO2/cordierite monolith, LaCoO3/TiO2/cordierite monolith were prepared by using aluminum oxide, silicon dioxide and titanium dioxide nanoparticles as washcoat and monolithic cordierite as the monolithic ceramic substrate.The obtained samples were characterized by means of XRD, SEM, EDS, BET, and ultrasonic vibration test (Medi II Pselecta). The surface area of the cordierite monolith-supported LaCoO3/ɤ-Al2O3 is larger than those of LaCoO3/SiO2 and LaCoO3/TiO2. The coating of alumina, silica oxide and titania nanoparticles could increase the surface area of monolithic cordierite and also endue the coated layer with engineered structure. The results of thermal treatment experiment indicate that the good thermal stability of the ɤ-Al2O3 coating on the cordierite. The ultrasonic vibration test results showed that the washcoat was adhered to the substrate strongly. The weight loss for the samples LaCoO3/ɤ-Al2O3/cordierite (the most desired preparation protocol in this study) eventually reached about 3%, which was considered as a low weight loss.The LaCoO3/ɤ-Al2O3/cordierite monolith catalysts were successfully prepared by coating ready-made 3DOM LaCoO3 (perovskite-type oxides) catalysts onmonolithic cordierite substrate with a dip-coating method by employing aluminasol for the first time. The catalytic activities of a series of monolithic catalystsLaCoO3/ɤ-Al2O3/cordierite, LaCoO3/ɤ-Al2O3/cordierite (3DOM-catalysts), LaCoO3/SiO2/cordierite, LaCoO3/TiO2/cordierite were evaluated for soot combustion. Thenano LaCoO3/ɤ-Al2O3/cordierite catalysts gave the highest catalytic activity for soot combustion among the studied catalysts. The T10, T50, T90 over the LaCoO3/ɤ-Al2O3/cordierite catalyst were 199.4 °C, 340.5 °C, 405.3 °C, respectively, and sco2m was 99.9%.Coating and Catalytic Performance of LaCoO3/Washcoat/Cordierite Monolith Catalysts for Soot Oxidation.Download high-res image (108KB)Download full-size image

We successfully synthesized 3D ordered macroporous (OM) Pt@CeO2−x/ZrO2 catalysts by a co-precipitation method. This series of catalysts have a well-defined 3D-OM structure. We investigated the activity of the 3D-OM Pt@CeO2−x/ZrO2 catalysts with different shell thicknesses, and systematically studied the adsorption and desorption of NO on the 3D-OM Pt@CeO2−x/ZrO2via in situ DRIFTS. The 3D-OM support enhances the contact efficiency between the solid reactant and catalyst, while the Pt@CeO2−x core–shell nanoparticles with strong Pt–CeO2−x interaction lead to a larger number of active species. With increasing the Ce/Pt molar ratio, the thickness of the shell becomes larger and the activity of Pt@CeO2−x/ZrO2 becomes lower. Among the as-prepared core–shell catalysts tested, the 3D-OM Pt1.0@CeO2−x/ZrO2-1 catalyst with the proper thickness of CeO2−x nanolayer shell showed the highest catalytic activity for soot combustion.

•Bifunctional catalysts of AuPd core-shell NPs decorated 3DOM TiO2 were fabricated by one-pot method.•The slow photon effect of 3DOM structure can enhance the light-harvesting efficiency.•Bimetallic AuPd NPs can promote the separation efficiency of photo-generated charge carrier.•AuPd/3DOM-TiO2 catalysts exhibit excellent photocatalytic activity for CO2 reduction.•The molar ratio of Au/Pd can adjust photocatalytic activity and selectivity for CO2 reduction.The photocatalytic conversion of CO2 and H2O into value-added chemicals using sunlight is significant to solve energy crisis and environmental problems. In this work, a series of novel bifunctional catalysts of core-shell structured AuPd nanoparticles decorated 3DOM TiO2 (AuPd/3DOM-TiO2) w were successfully fabricated via a facile one-pot method of gas bubbling-assisted membrane reduction (GBMR). AuPd/3DOM-TiO2 catalysts show uniform 3D ordered macroporous structure, and the slow photon effect of 3DOM-TiO2 as a photonic crystal can enhance light-harvesting efficiency. AuPd nanoparticles are highly dispersed on the surface of 3DOM-TiO2 carrier. Since bimetallic AuPd nanoparticles with the relatively low Fermi level have good capacity of trapping electron, they can efficiently promote the separation of photogenerated electron-hole pairs in TiO2. The AuPd/3DOM-TiO2 catalysts exhibit excellent photocatalytic activity for CO2 reduction with H2O to CH4 under light irradiation. Among the studied catalysts, Au3Pd1/3DOM-TiO2 catalyst exhibits the highest photocatalytic activity and selectivity for CO2 reduction, e.g., its formation rate of CH4 is 18.5 μmol g−1 h−1 and its selectivity to CH4 production by CO2 reduction is 93.9%. The possible mechanism of AuPd/3DOM-TiO2 catalysts for photocatalytic CO2 reduction is also proposed, and it would guide further design and synthesis of high efficient photocatalysts for CO2 reduction with H2O.Download high-res image (196KB)Download full-size image

Three-dimensionally ordered macroporous (3DOM) SiO2 was synthesized by a colloidal crystal template (CCT) method, and 3DOM SiO2-supported transition metal oxides catalysts were prepared by a facile incipient-wetness impregnation method. The as-prepared catalysts show well-defined three-dimensionally ordered macroporous structures. The transition metal oxides formed different sizes of nanoparticles and loaded onto 3DOM SiO2. The as-prepared catalysts show high catalytic activities for soot combustion. Among the studied catalysts, the 3DOM MnOx/SiO2 catalyst (molar ratio of Mn to Si is 1:4) shows the highest catalytic activity among the studied catalysts, e.g. T10, T50 and T90 are 297, 355 and 393 °C, respectively, and SmCO2 is 95.5%. The catalytic performances of 3DOM SiO2-supported transition metal oxide catalysts are mainly controlled by three factors: the macroporous effects of the 3DOM structure, the redox properties of transition metal oxides and the sizes of transition metal oxide NPs. 3DOM SiO2-supported transition metal oxide catalysts are promising for practical applications in soot combustion owing to high activity and low cost.

3D ordered macroporous (3DOM) TiO2 was synthesized by the method of colloidal crystal template (CCT) using tetrabutyl titanate as precursor solution, and the photocatalysts of the 3DOM TiO2-supported CeO2 nanolayer with different weight ratios of CeO2 to TiO2 were successfully prepared by the gas bubbling-assisted membrane precipitation (GBMP) method. The catalysts were systematically characterized by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), mercury intrusion porosimetry (MIP), X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance spectroscopy (DRS), and photoluminescence spectra (PL). The slow light effect of photonic crystal (3DOM structure) can enhance absorption efficiency of solar irradiation. Moreover, the introduction of CeO2 nanolayers can effectively extend the photoresponse from UV to visible region and improve the separation of photogenerated electron–hole pairs. The photocatalytic activities for the reduction of CO2 with H2O were evaluated by the production of main product (CO). 3DOM CeO2/TiO2 photocatalysts exhibit high catalytic activity for the photocatalytic reduction of CO2 with H2O under simulated solar irradiation.

Three-dimensionally ordered macroporous (3DOM) MnxCe1–xOδ oxides with different ratios of Mn to Ce were successfully synthesized by colloidal crystal template (CCT) method, and 3DOM Pt/Mn0.5Ce0.5Oδ with varied Pt loadings were prepared by in situ ethylene glycol (EG) reduction method. 3DOM MnxCe1–xOδ supports exhibited well-defined 3DOM nanostructure, and Pt nanoparticles (NPs) with 1–2 nm size were evenly dispersed on the inner walls of uniform macropores. Among 3DOM MnxCe1–xOδ catalysts, 3DOM Mn0.5Ce0.5Oδ showed excellent catalytic activity for soot combustion; i.e., T50 is 358 °C and SCO2m is 94.2%. 3DOM Pt/Mn0.5Ce0.5Oδ catalysts exhibited higher activity than 3DOM MnxCe1–xOδ and 3 wt % Pt/Mn0.5Ce0.5Oδ showed the highest catalytic activity for soot combustion (T50 is 342 °C and SCO2m is 96.7%). Macropores effect, synergistic effects between Mn and Ce, and synergistic effects between Pt and Mn0.5Ce0.5Oδ support are contributed to high catalytic activities of as-prepared catalysts.

We successfully synthesized 3D ordered macroporous (OM) Pt@CeO2−x/ZrO2 catalysts by a co-precipitation method. This series of catalysts have a well-defined 3D-OM structure. We investigated the activity of the 3D-OM Pt@CeO2−x/ZrO2 catalysts with different shell thicknesses, and systematically studied the adsorption and desorption of NO on the 3D-OM Pt@CeO2−x/ZrO2via in situ DRIFTS. The 3D-OM support enhances the contact efficiency between the solid reactant and catalyst, while the Pt@CeO2−x core–shell nanoparticles with strong Pt–CeO2−x interaction lead to a larger number of active species. With increasing the Ce/Pt molar ratio, the thickness of the shell becomes larger and the activity of Pt@CeO2−x/ZrO2 becomes lower. Among the as-prepared core–shell catalysts tested, the 3D-OM Pt1.0@CeO2−x/ZrO2-1 catalyst with the proper thickness of CeO2−x nanolayer shell showed the highest catalytic activity for soot combustion.