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Rhodium-based manganese oxide frameworks were explored as a prototype for carbon dioxide reactive capture and conversion. Three-dimensional frameworks of MnOx were utilized as support structures to isolate Rh metal centers. V, Na, and Zn were introduced as counterions to stabilize the structure and for their beneficial effect as promoters. With this multicomponent catalyst, Rh active centers with MnOxs and varied counterions, we were able to selectively tune the catalytic performance of the material via the choice of counterion and structure of the host material. With cryptomelane-type tunnel manganese oxides octahedral molecular sieve (OMS2), we found that Rh-V-OMS2 was highly stable even after 48 hours on stream with a reaction rate of around 1.5×10−4 mol CO 2 /g Rh /s, surpassing the net reactivity of other initially more active combinations. Furthermore, during CO 2 hydrogenation, in situ XAFS showed that single Rh atoms nucleated into nanoparticles/ sub-nanometer clusters with a coordination number of 5.5 or less. Our finding of the correlation between the reaction rate and particle size offers the potential for enhanced control over the reaction rate by tuning particle size. Our activity study with control experiments demonstrates that the activities of the catalysts are proved due to the unique metal support interaction offered by the Rh-X-MnO. [Display omitted] • Rhodium within Manganese framework promote active and stable CO2 Hydrogenation. • In situ XAFS shows Rh nucleation to stable active size under CO2 Hydrogenation. • Remarkable activity and stability over 50 hours found for Rh-V-MnOx system for RWGS • In situ DRIFTS correlated with XAFS link surface species to Rh structure. [ABSTRACT FROM AUTHOR]

The CO and H 2 (syngas) production from methane partial oxidation (MPO) using TiO 2 supported Au-Pd bimetallic catalysts are discussed. The supported Au, Pd and Au-Pd bimetallic nanoparticles were prepared by an incipient wetness impregnation or co-impregnation method and were characterized. The supported Au-Pd catalyst was selective for reforming and was more active compared to bare TiO 2 , TiO 2 supported Au only, or Pd only catalysts. The catalyst properties before and after MPO reaction were investigated, including the stability of the TiO 2 support, and the stability of Au and Pd nanoparticles. The supported Au-Pd catalyst has the highest TON (TON H2  = 23 at 650 °C), compared to supported Au catalyst (TON H2  < 1) and supported Pd catalyst (TON H2  < 1). Based on the analysis of outlet gases from the MPO reaction in a flow reactor, synergetic effects between Au and Pd, where Pd activates C H bonds while gold modulates the behavior of oxygen at the catalyst surface, are shown to contribute to MPO. Additionally, the Au-Pd/TiO 2 material shows long-term activity (>12 h) for the MPO reaction at 600 °C. [ABSTRACT FROM AUTHOR]

Abstract: A long-standing goal of chemistry is to synthesize organic compounds from CO2 and H2O to mimic natural photosynthetic processes. Achieving this goal requires catalysts and methods that activate CO2 and split water simultaneously. Here we report such catalysts and methods for the synthesis of paraformaldehyde from CO2 and H2O at atmospheric pressure. The activation was realized by polarizing metal/metal oxide interfaces with a DC voltage or current. The selectivity to paraformaldehyde was as high as 100% and CO2 conversion up to 8%. Both Pt/CSZ and Pt/MnO2 catalysts with ionic conductivity and mixed conductivity respectively produced paraformaldehyde. The former works at high temperatures of 600–900°C; the latter works at low temperatures of 300–450°C. This gas-phase electrocatalysis technique provides new insight into the utilization of CO2 as a carbon source in organic chemical syntheses and in the clean activation of CO2. [Copyright &y& Elsevier]

Abstract: A synthesized γ-MnO2 octahedral molecular sieve was characterized and used to catalyze solvent-free atmospheric oxidation of toluene with molecular oxygen. The γ-MnO2 showed excellent catalytic activity and good selectivity under the mild atmospheric reflux system at a low temperature (110°C). Under optimized conditions, a 47.8% conversion of toluene, along with 57% selectivity of benzoic acid and 15% of benzaldehyde were obtained. The effects of reaction time, amount of catalyst and initiator, and the reusability of the catalyst were investigated. [Copyright &y& Elsevier]

Abstract: Hydrogen adsorption on Ru surfaces of Ru/TiO2 catalysts has been investigated in a gas adsorption apparatus at temperatures from 35 to 150°C, H2 partial pressures from 0.05 to 700Torr, and adsorption equilibration time at each pressure from 3 to 60min. Results showed that adsorption of H2 on the TiO2 support are negligible. TEM measurements suggested that there was no strong metal–support interaction (SMSI) on the synthesized Ru/TiO2 samples to inhibit H2 adsorption. A transition pressure point of ∼60Torr was observed for H2 adsorption on Ru/TiO2. Most of the strong chemisorption occurs before this transition pressure and weak chemisorption happens thereafter. H2 adsorption increases with temperatures from 35 to 75°C indicating an activation energy present for H2 chemisorption on Ru. Above 75°C, the adsorption slightly decreases with further increase of temperature up to 150°C. Monolayer coverage was attained at 75°C for 30min equilibration time with a H2 pressure higher than 300Torr. Monolayer H2 chemisorption was used to determine Ru metal particle size in Ru/TiO2 systems compared with XRD and TEM analyses. Selected area electron diffraction (SAD) indicated that there was no preferred crystallographic orientation of the TiO2 supported Ru. Therefore, exposed Ru atoms equally contribute from the three low-index planes [(001), (100), and (110)] with the highest atomic density instead of only the (100) plane for conventional treatments. With this assumption, the average Ru particle size calculated from H2 chemisorption (4.6nm) agrees with the TEM measurements (4.1nm). [Copyright &y& Elsevier]