Identifying the descriptor governing NO oxidation on mullite Sm(Y, Tb, Gd, Lu)Mn₂O₅for diesel exhaust cleaning

Abstract

Mn-based oxides Sm(Y, Tb, Gd, Lu)Mn2O5 are synthesized to identify a general descriptor that governs the catalytic performance in NO oxidation.

Ionic transport processes in polymer mixture solutions based on quaternized polysulfones

“…Polysulfones, produced through polycondensation, are known as high-performance materials with superior thermal, chemical, and mechanical properties, which represents an advantage for many applications, such as filtration membranes [28][29][30][31][32], coatings [33,34], composites [35][36][37], microelectronic devices [38], thin film technology [39], biomaterials [25,37,40], and fuel cells [41][42][43][44]. Introduction of functional groups into polysulfones solves some limitations, and also extends the range of potential applications of these high-performance materials through the specific properties gained, and thus provides wider scope.…”

Earth‐Abundant Transition Metal‐Based Mullite‐Type Oxide Catalysts for Heterogeneous Oxidation Reactions

“…HT synthesis causes crystal growth at lower temperatures than the CP method, which results in high‐surface‐area materials desirable for heterogeneous catalysis and has been successfully used to prepare mullite oxides. [ 43,44,61–64 ] To synthesize AMn 2 O 5 , the metal salt precursors of A, Mn, and KMnO 4 are mixed in a molar ratio of 5:7:3 in DI water and then a precipitating agent (NaOH or KOH) is added dropwise. The HT treatment is conducted at 180–200 °C for 24–48 h in an autoclave under autogenous pressure.…”

“…The HT treatment is conducted at 180–200 °C for 24–48 h in an autoclave under autogenous pressure. [ 43,44,61–64 ] The mullite oxide catalysts prepared by this method exhibit high specific surface area with narrow particle size distribution and well‐controlled morphologies. For example, Ma et al synthesized SmMn 2 O 5 with different morphologies such as nanorods and nanoparticles by varying the pH and HT reaction time.…”

“…The high‐spin d ‐band configuration for Mn 4+ in Mn oct is given as t 2g 3 , and e g orbital is empty, whereas, for Mn 3+ in the Mn pyr crystal field, d ‐band splitting occurs as d xz 1 , d yz 1 , d xy 1 , and d z2 1 (Figure 4a, bottom panel). [ 42,61 ] As d z2 orbital in the Mn pyr crystal field has a larger overlap with the O 2 p orbital, its orbital filling governs the Mn 3+ O bond strength and hence the activity. For all AMn 2 O 5 , the d z2 occupancy of Mn 3+ in Mn pyr is 1 (Figure 4a, bottom panel) irrespective of the A‐site element used.…”

Modest Oxygen‐Defective Amorphous Manganese‐Based Nanoparticle Mullite with Superior Overall Electrocatalytic Performance for Oxygen Reduction Reaction

“…Distinct from the widely studied perovskite‐ and spinel‐type oxides, Mn‐based mullites with the general formula A″Mn 2 O 5 , whereas A″ is the trivalent rare‐earth metal ion, incorporate equivalent amount of Mn 3+ and Mn 4+ (i.e., Mn 3+ /Mn 4+ = 1) at square‐pyramidal and octahedral sites, respectively ( Figure a). Recent density functional theory (DFT) calculations identified that the d z2 orbital of Mn pyr 3+ (Figure b) largely overlapped with the O‐2p orbital of the adsorbed oxygen, and the strength of oxygen adsorption on the Mn pyr 3+ site was moderate, suggesting potentially favorable exchange kinetics of OH − by O 2 which was considered to limit ORR kinetics on metal oxides. [4a,10] Besides, the mullite SmMn 2 O 5 micropowder has exhibited acceptable ORR activity .…”