Pd-Doped Perovskite: An Effective Catalyst for Removal of NO_<i>x</i> from Lean-Burn Exhausts with High Sulfur Resistance

Herein, we report the Pd-doped perovskite La0.7Sr0.3CoO3 as an effective lean NOx trap (LNT) catalyst. This smart perovskite displays excellent NOx reduction activities for lean-burn exhausts (NOx conversion >90%, N2 selectivity >90%) over a wide operating temperature range (275–400 °C), as well as an extremely high sulfur tolerance. Our results evidenced Pd dissolving into or segregating out of perovskite in lean-burn and fuel-rich atmospheres. The segregated metallic Pd from perovskite in fuel-rich atmospheres is crucial for obtaining these promising achievements. These findings provide a new possibility for the application of the Pd-based LNT catalysts

Facilely Synthesized H‑Mordenite Nanosheet Assembly for Carbonylation of Dimethyl Ether

Hard coke blockage of micropores of acidic zeolites generally causes serious catalytic deactivation for many chemical processes. Herein, we report a facile method to synthesize H-mordenite nanosheet assemblies without using any template agent. The assemblies exhibit the high catalytic activity for carbonylation of dimethyl ether because of their large quantity of framework Brønsted acids. The specific morphology of the nanosheet unites improves mass diffusion for both reactants and products. Consequently, the coke precursor species can readily migrate from the micropores to the external surface of the assemblies, inducing the improved catalytic stability through inhibiting hard coke formation in frameworks

Hydrotalcite-Derived Mn_<i>x</i>Mg_3−<i>x</i>AlO Catalysts Used for Soot Combustion, NO_<i>x</i> Storage and Simultaneous Soot-NO_<i>x</i> Removal

The hydrotalcite-based MnxMg3−xAlO catalysts with different Mn:Mg atomic ratios were synthesized by coprecipitation, and employed for soot combustion, NOx storage and simultaneous soot-NOx removal. It is shown that with the increase of Mn content in the hydrotalcite-based MnxMg3−xAlO catalysts the major Mn-related species vary from MnAl2O4 and Mg2MnO4 to Mn3O4 and Mn2O3. The catalyst Mn1.5Mg1.5AlO displays the highest soot combustion activity with the temperature for maximal soot combustion rate decreased by 210 °C, as compared with the Mn-free catalyst. The highly reducible Mn4+ ions in Mg2MnO4 are identified as the most active species for soot combustion. For NOx storage, introduction of Mn greatly influences bulk NOx storage, with the adsorbed NOx species varying from linear nitrites to ionic and chelating bidentate nitrates gradually. The coexistence of highly oxidative Mn4+ and highly reductive Mn2+ in Mn1.0Mg2.0AlO is favorable to the simultaneous soot-NOx removal, giving a NOx reduction percentage of 24%. In situ DRIFTS reveals that the ionic nitrate species are more reactive with soot than nitrites and chelating bidentate nitrates, showing higher NOx reduction efficiency

Coaddition of Phosphorus and Proton to Graphitic Carbon Nitride for Synergistically Enhanced Visible Light Photocatalytic Degradation and Hydrogen Evolution

Graphitic carbon nitride (g-C3N4) has attracted enormous attention in photocatalysis owing to its special structure and properties. The insufficient light absorption and fast charge-carrier recombination limit its further photocatalytic application. Herein, we report a facile approach to fabrication of the g-C3N4 modified simultaneously with phosphorus and proton by directly heating the mixture of urea phosphate (UP) and urea in air. The incorporation of the phosphorus atoms in g-C3N4 can significantly decrease the band gap, leading to the enhanced light absorption efficiency. Furthermore, UP can also introduce the protons to the structure of g-C3N4 from protonation. The protons can inhibit the recombination of the charge carriers and improve their utilization. The synergistic effect of the phosphorus doping and protonation in g-C3N4 results in the superior visible-light photocatalytic performance for both degradation of Rhodamine B (RhB) and H2 evolution from water splitting. We believe that our findings have a broad applicability to design efficient and novel g-C3N4-based photocatalysts