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This study reports the low temperature and low pressure conversion (up to 160 °C, p = 3.5 bar) of CO2 and H2 to CO using plasmonic Au/TiO2 nanocatalysts and mildly concentrated artificial sunlight as the sole energy source (up to 13.9 kW·m−2 = 13.9 suns). To distinguish between photothermal and non-thermal contributors, we investigated the impact of the Au nanoparticle size and light intensity on the activity and selectivity of the catalyst. A comparative study between P25 TiO2-supported Au nanocatalysts of a size of 6 nm and 16 nm displayed a 15 times higher activity for the smaller particles, which can only partially be attributed to the higher Au surface area. Other factors that may play a role are e.g., the electronic contact between Au and TiO2 and the ratio between plasmonic absorption and scattering. Both catalysts displayed ≥84% selectivity for CO (side product is CH4). Furthermore, we demonstrated that the catalytic activity of Au/TiO2 increases exponentially with increasing light intensity, which indicated the presence of a photothermal contributor. In dark, however, both Au/TiO2 catalysts solely produced CH4 at the same catalyst bed temperature (160 °C). We propose that the difference in selectivity is caused by the promotion of CO desorption through charge transfer of plasmon generated charges (as a non-thermal contributor). [ABSTRACT FROM AUTHOR]

The preparation of Ru nanoparticles supported on γ-Al2O3 followed by chemical reduction using RuCl3 as a precursor is demonstrated, and their properties are compared to Ru nanoparticles supported on γ-Al2O3 prepared by impregnation of γ-Al2O3 with Ru3(CO)12 and subsequent thermal decomposition. The Ru nanoparticles resulting from chemical reduction of RuCl3 are slightly larger (1.2 vs. 0.8 nm). In addition, Ru nanoparticles were deposited on Stöber SiO2 using both deposition techniques. These particles were larger than the ones deposited on γ-Al2O3 (2.5 and 3.4 nm for chemical reduction and thermal decomposition, respectively). Taking into account the size differences between the Ru nanoparticles, all catalysts display similar activity (0.14–0.63 mol·gRu−1·h−1) and selectivity (≥99%) in the sunlight-powered Sabatier reaction. Ergo, the use of toxic and volatile Ru3(CO)12 can be avoided, since catalysts prepared by chemical reduction of RuCl3 display similar catalytic performance. [ABSTRACT FROM AUTHOR]

Plasmon catalysis is an interesting technology concept for powering chemical processes with light. Here, we report the use of various Al2O3‐supported Ru spheroidal nanoparticles as catalyst for the low‐temperature conversion of CO2 and H2 to CH4 (Sabatier reaction), using sunlight as energy source. At high loadings of Ru spheroidal nanoparticles (5.9 % w/w), we observe a sharp increase in the rate of the sunlight powered reaction when compared to the reaction in dark at the same catalyst bed temperature. Based on our results we exclude plasmon coupling as cause, and attribute the rate enhancement to collective photothermal heating of the Al2O3‐supported Ru nanoparticles. [ABSTRACT FROM AUTHOR]

[Display omitted] • Plasma catalytic CO 2 dissociation was performed in packed bed DBD plasma reactor over core-shell SiO 2 @TiO 2 spheres. • Concentration of Ti(IV) solution and the addition of a binder has an impact on uniform coating. • Surface morphology of TiO 2 shell influences CO 2 activity. • Maximum conversion of 37.7% obtained for core-shell SiO 2 @TiO 2 -0.25M+LUDOX at a certain flow rate. Plasma catalysis, a promising technology for conversion of CO 2 into value-added chemicals near room temperature, is gaining increasing interest. A dielectric barrier discharge (DBD) plasma has attracted attention due to its simple design and operation at near ambient conditions, ease to implement catalysts in the plasma zone and upscaling ability to industrial applications. To improve its main drawbacks, being relatively low conversion and energy efficiency, a packing material is used in the plasma discharge zone of the reactor, sometimes decorated by a catalytic material. Nevertheless, the extent to which different properties of the packing material influence plasma performance is still largely unexplored and unknown. In this study, the particular effect of synthesis induced differences in the morphology of a TiO 2 shell covering a SiO 2 core packing material on the plasma conversion of CO 2 is studied. TiO 2 has been successfully deposited around 1.6–1.8 mm sized SiO 2 spheres by means of spray coating, starting from aqueous citratoperoxotitanate(IV) precursors. Parameters such as concentration of the Ti(IV) precursor solutions and addition of a binder were found to affect the shells' properties and surface morphology and to have a major impact on the CO 2 conversion in a packed bed DBD plasma reactor. Core-shell SiO 2 @TiO 2 obtained from 0.25 M citratoperoxotitante(IV) precursors with the addition of a LUDOX binder showed the highest CO 2 conversion 37.7% (at a space time of 70 s corresponding to an energy efficiency of 2%) and the highest energy efficiency of 4.8% (at a space time of 2.5 s corresponding to a conversion of 3%). [ABSTRACT FROM AUTHOR]

Abstract: The effect of a supercritical carbon dioxide (scCO2) treatment on the free volume of poly[1-(trimethylsilyl)-1-propyne] (PTMSP) and PTMSP-silica nanohybrid membranes was investigated with positron annihilation lifetime spectroscopy (PALS) and correlated with their performance in pervaporation. Treatment of dense unfilled PTMSP and silica filled PTMSP (2.5, 10 and 20wt.% silica) membranes with scCO2 at different pressures and temperatures, resulted in a clear increase in the mean free volume size and an enhanced performance in the pervaporative separation of an aqueous ethanol mixture. Specific permeation rate increases up to 76% were observed for the unfilled membranes treated with scCO2 at 70°C and 24MPa. The scCO2-treatment could thus be seen as an effective alternative to PTMSP-silica (50wt.%) membranes, which cause a 72% increase in specific permeation rate. Moreover, the ethanol concentration in the permeate increases significantly upon treating the membranes with scCO2. [Copyright &y& Elsevier]