Cyclooligomers. In their Communication (e202312040), Uwe Bunz, Jan Freudenberg, Klaus Müllen et al. report the solvent‐ and catalyst‐free thermolysis of arylated biphenylenes, providing one‐step ...access to ncyclo‐ortho‐phenylenes.
Supported Pt-based catalysts have been identified as highly selective catalysts for CO oxidation, but their potential for applications has been hampered by the high cost and scarcity of Pt metals as ...well as aggregation problems at relatively high temperatures. In this work, nanorod structured (TiOsub.2−Pt)/CeOsub.2 catalysts with the addition of 0.3 at% Pt and different atomic ratios of Ti were prepared through a combined dealloying and calcination method. XRD, XPS, SEM, TEM, and STEM measurements were used to confirm the phase composition, surface morphology, and structure of synthesized samples. After calcination treatment, Pt nanoparticles were semi-inlayed on the surface of the CeOsub.2 nanorod, and TiOsub.2 was highly dispersed into the catalyst system, resulting in the formation of (TiOsub.2−Pt)/CeOsub.2 with high specific surface area and large pore volume. The unique structure can provide more reaction path and active sites for catalytic CO oxidation, thus contributing to the generation of catalysts with high catalytic activity. The outstanding catalytic performance is ascribed to the stable structure and proper TiOsub.2 doping as well as the combined effect of Pt, TiOsub.2, and CeOsub.2. The research results are of importance for further development of high catalytic performance nanoporous catalytic materials.
Under DFT calculations, a systematic investigation is carried out to explore the structures and oxygen evolution reaction (OER) catalytic activities of a series of 2D single-atom catalyst (SAC) ...systems, which are constructed by doping the transition metal (TM) atoms in group VIII into the cavities of rigid phthalocyanine carbide (pc-Csub.3Nsub.2). We can find that when Co, Rh, Ir and Ru atoms are doped in the small or large cavities of a pc-Csub.3Nsub.2 monolayer, they can be used as high-activity centers of OER. All these four new TM@Csub.3Nsub.2 nanostructures can exhibit very low overpotential values in the range of 0.33~0.48 V, even smaller than the state-of-the-art IrOsub.2 (0.56 V), which indicates considerably high OER catalytic activity. In particular, the Rh@Csub.3Nsub.2 system can show the best OER performance, given that doped Rh atoms can uniformly serve as high-OER-active centers, regardless of the size of cavity. In addition, a detailed mechanism analysis was carried out. It is found that in these doped pc-Csub.3Nsub.2 systems, the number of outer electrons, the periodic number of doped TM atoms and the size of the embedded cavity can be considered the key factors affecting the OER catalytic activity, and excellent OER catalytic performance can be achieved through their effective cooperation. These fascinating findings can be advantageous for realizing low-cost and high-performance SAC catalysts for OER in the near future.
The research of high efficiency low platinum materials for oxygen reduction reaction (ORR) attracts attention in the field of energy conversion and storage. This study reports a high-efficient ...ternary ORR electrocatalyst containing N-doped carbon/CeO.sub.2-supported platinum catalyst (Pt/CeO.sub.2/N-C) with extremely low Pt content, which is fabricated by a facile two-step procedure using polyaniline (PANI) as an N source. The doped chloroplatinic anions are reduced to form evenly dispersed Pt nanoparticles (NPs) incorporated with the N-doped carbon matrix. A combination of Pt NPs with exposed highly active (111) facets, CeO.sub.2, and active pyridinic N contributed to enhanced ORR performance and stability. The activity of our Pt.sub.0.1/CeO.sub.2/N-C catalyst containing only 5.6 wt% of Pt reaches 238.46 mA mg .sub.Pt.sup.-1, four times advanced than commercial 20%Pt/C catalyst (58.8 mA mg .sub.Pt.sup.-1). These findings reveal an important new strategy for designing high-yield and cost-effective Pt-based ORR catalysts in simple and easy way.
A simple Co(ii)-based amine–borane dehydropolymerisation catalyst system is reported that operates at low loadings, to selectively give (H2BNMeH)n polymer on scale, with catalyst control over Mn, ...narrow dispersities and low residual metal content.
Gas turbines produce a large amount of NOsub.x and CO due to high temperatures and insufficient combustion. Through the selective catalytic reduction of NO with CO (CO-SCR) in a gas turbine, the ...activities of the Mn-Fe-Ce/FA catalyst using fly ash (FA) as a carrier under different atmospheres were studied. The catalysts prepared by calcining different active materials under different atmospheres were used to analyze their denitrification abilities and resistance to water vapor. The denitrification performance of the catalyst prepared under reducing atmosphere is about 30 percent higher than that of the catalyst prepared under air atmosphere, and the decarburization performance is about 40 percent higher. In the presence of oxygen, the denitrification rate and decarburization rate of the 1:1 ratio of the Mn-Ce catalyst reach 67.16% and 59.57%, respectively. In an oxygen-containing atmosphere, the catalyst prepared by replacing Ce with Fe shows better denitrification and decarburization performances, which are 78.56% and 78.39%, respectively. When the flue gas space velocity is 4000 hsup.−1 and the carbon-nitrogen ratio is 1.6, the catalyst shows better performance. After the water vapor is introduced, the denitrification and decarbonization rates of the catalyst decrease by about 10% and 9%, respectively. After ceasing water vapor, it rebounds by about 8%, and the activity could not be fully restored. However, the catalyst still shows strong water resistance in general.
Chlorine species, widely presented in industrial flue gas such as the waste incineration plants, can poison the catalysts and affect the selective catalytic reduction (SCR) performance. In this work, ...effects of Cl on the SCR performance of V.sub.2O.sub.5-WO.sub.3/TiO.sub.2 (VW/Ti) catalysts were investigated by NH.sub.4Cl deposition. The results showed that the NO.sub.x conversion efficiency at low reaction temperature (< 300 °C) decreased with the loading of NH.sub.4Cl after calcination. It was found that instead of causing the chlorination of VW/Ti catalyst the NH.sub.4Cl decomposed into volatile Cl species due to the weak V-Cl bonding. Such decomposition reduced significantly the surface non-lattice oxygen species to inhibit NO adsorption and activation, but hardly affected the redox ability and acidity of VW/Ti catalyst. Time-resolved in situ DRIFTs results indicated that NH.sub.3 activation and the SCR process predominated by Eley-Rideal mechanism were not influenced with NH.sub.4Cl impregnation, while the SCR at low temperature following a Langmuir-Hinshelwood path was limited by the decreased and weaker binding sites for NO activation.
Catalytic conversion of COsub.2 to CO via the reverse water gas shift (RWGS) reaction has been identified as a promising approach for COsub.2 utilization and mitigation of COsub.2 emissions. Bare Pt ...shows low activity for the RWGS reaction due to its low oxophilicity, with few research works having concentrated on the inverse metal oxide/Pt catalyst for the RWGS reaction. In this work, MnOsub.x was deposited on the Pt surface over a SiOsub.2 support to prepare the MnOsub.x/Pt inverse catalyst via a co-impregnation method. Addition of 0.5 wt% Mn to 1 wt% Pt/SiOsub.2 improved the intrinsic reaction rate and turnover frequency at 400 °C by two and twelve times, respectively. Characterizations indicate that MnOsub.x partially encapsulates the surface of the Pt particles and the coverage increases with increasing Mn content, which resembles the concept of strong metal–support interaction (SMSI). Although the surface accessible Pt sites are reduced, new MnOsub.x/Pt interfacial perimeter sites are created, which provide both hydrogenation and C-O activation functionalities synergistically due to the close proximity between Pt and MnOsub.x at the interface, and therefore improve the activity. Moreover, the stability is also significantly improved due to the coverage of Pt by MnOsub.x. This work demonstrates a simple method to tune the oxide/metal interfacial sites of inverse Pt-based catalyst for the RWGS reaction.
Mn-Ce/TiO.sub.2 catalysts were co-pretreated with SO.sub.2 and Ca and applied for the selective catalytic reduction (SCR) of NO with ammonia. The effect of co-pretreatment of SO.sub.2 and Ca on the ...physicochemical properties of catalysts was investigated by BET, XRD, XPS, NH.sub.3-TPD, H.sub.2-TPR, and UV-Vis techniques. The results show the co-pretreatment of SO.sub.2 and Ca greatly influences the physicochemical properties of catalysts such as texture characteristics, surface acidity and redox ability, amounts of active species and surface OH group, and therefore affects the catalytic activity of catalysts. The Mn-Ce-Ti(S-OH) catalyst co-pretreated with SO.sub.2 and Ca(OH).sub.2 exhibits better catalytic activity than Mn-Ce-Ti(S-Cl) catalyst co-pretreated with SO.sub.2 and CaCl.sub.2. The Mn-Ce-Ti(S-OH) catalyst possesses larger specific surface area, higher concentrations of surface active species and surface chemisorbed oxygen, better surface acidity and redox ability, which may contribute to the accelerated catalytic activity.
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