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Thermo-catalytic bio-SNG (CH 4) production is one of the useful tools for converting waste to gaseous fuels through CO 2 conversion. To abundant properly, however, efficient, robust and cost-effective catalysts would be required. Bimetallic systems based on transition metals seem to be promising candidates for this task. The CoCu bimetallic system with in-situ generated interfaces was synthesized and used as a catalyst for CO 2 methanation. The in-depth analysis of the structure-activity-selectivity relationships involving XRD, (NAP-)XPS, EXAFS and TEM-EDX revealed that the co-existence of Co0, CoO, and Cu0 in the proper distribution on the surface can ensure the selective production of methane. To fine-tune the surface composition of the bimetallic systems, a systematic alteration of the Cu:Co ratio in the precursor spinel structures must be performed. Cu 0.4 Co 2.6 O 4 derivative, stabilizing subsurface Cu(I)–O specimen, showed the best performance with high activity (12,800 nmol g–1 s–1) and a remarkable selectivity of 65–85% for methane in a wide temperature range (250–425 °C). In studying the mechanistic aspects of methanation, it has been shown that the hydrogenation of active carbon at the surface or below the surface is the key step for the production of methane. So far, this cobalt-catalyzed sub-step has been proposed in catalytic Fischer-Tropsch syntheses. [Display omitted] • Copper cobaltites are useful precursors for the construction of efficient Cu/Co bimetallic catalysts for CO 2 methanation. • The copper-to-cobalt ratios in the octahedral lattice positions of the spinels determined the catalytic performance. • The Cu 0.4 Co 2.6 O 4 derivative with a Co-enriched surface shows high performance producing CH 4 over a wide temperature range. • The hydrogenation of active carbon at the surface or below the surface is the key step for the production of methane. [ABSTRACT FROM AUTHOR]

The decomposition of C 3 H 8 and its reaction with CO 2 have been investigated on Au deposited on ZnO, MgO and Al 2 O 3 . The reactions proceeded above 650–700 K. The conversion of C 3 H 8 was only few percents on Au/MgO and Au/Al 2 O 3 , even at 873 K, but reached ∼17% on Au/ZnO. The selectivity of propylene formation was about 56%. CO 2 only slightly affected the reaction of C 3 H 8 on Au/Al 2 O 3 and Au/MgO, but significantly enhanced the conversion of C 3 H 8 on Au/ZnO catalyst. The formation of large amount of CO indicates the involvement of CO 2 in the reaction of C 3 H 8 . From the product distribution it was inferred that beside the oxidative dehydrogenation and dry reforming reaction, the decomposition of C 3 H 8 into CH 4 and surface carbon also occurred. The effect of ZnO is explained by an electronic interaction between n-type ZnO and Au particles leading to a formation of reactive CO 2 − . [ABSTRACT FROM AUTHOR]

The dehydrogenation of C 2 H 6 and its reaction with CO 2 have been investigated on Au deposited on various oxides. Both reactions occurred at relatively high temperatures, above 650 K. Ethylene formed in the dehydrogenation process with high selectivity, 94–98%, on most of the catalysts. The conversion of C 2 H 6 varied with the nature of support and fell in the range of 3–19%. Adding CO 2 to C 2 H 6 only slightly influenced the reaction of C 2 H 6 on Au/MgO and Au/Al 2 O 3 , but markedly increased the conversion of C 2 H 6 and changed its reaction pathways on Au deposited on n -type TiO 2 , CeO 2 and ZnO. Taking into account the properties of these oxides, we came to the conclusion that their electric behavior and not their defect structure play a dominant role in the enhanced activity of Au deposited on these supports. Based on the different work functions, an electronic interaction between Au particles and these oxides is proposed, which facilitates the formation of reactive negatively charged CO 2 . [ABSTRACT FROM AUTHOR]

We report the enhanced photocatalytic performance of CO 2 reduction by introducing noble metal-deposited TiO 2 photocatalysts (NMD/TiO 2) under both visible light irradiation (VLI) and UV. It was found that NMD-TiO 2 samples demonstrated an expanded ability for light absorption, resulting in an improved photoefficiency for CO 2 reduction and selectivity towards carbon monoxide (CO). The conversion yields of CO 2 to CO followed the order: Rh >Ru >Pt and with Rh/TiO 2 reached 10.65 μmol/g cat (under visible light) and 7.84 μmol/g cat (under UV), which are ∼3 and 10 times more as compared to pristine anatase TiO 2 (0, and 2.43 μmol/g cat). Various factors were addressed including theoretical studies via DFT revealed that the formation of new impurity energy state levels in NMD/TiO 2 , which act as acceptor levels. Moreover, DRIFTS studies showed that the H-O-C-O and formyl (H 2 CO) species were the important intermediates towards the hydrogenation of CO 2 to CO. Also, a charge transfer mechanism toward CO 2 reduction was elucidated. [Display omitted] • Controlled-size noble metals/TiO 2 composite were used in CO 2 reduction under UV and visible light. • NMD-TiO 2 showed enhanced light absorption ability which lead to the highest yield of CO (10.65 μmol/gcat). • DFT revealed the formation of new impurity energy state levels, which act as acceptor levels. • DRIFTS showed H-O-C-O and formyl (H 2 CO) species were key intermediates in photo-RWGS. [ABSTRACT FROM AUTHOR]

[Display omitted] • <2 nm Pt, Ru and Rh NCs were anchored over CeO 2 /MCF17. • Supported metal NCs exhibited excellent catalytic performance for CO 2 reduction. • Ru NCs/CeO 2 exhibited ∼ 99% selectivity to CH 4. • Effect of two entirely different supports (CeO 2 and MCF 17) was evaluated. Efficient conversion of CO 2 into CH 4 and CO brings an important opportunity to get valuable feedstock for a variety of industrially important reactions as both CH 4 and CO are widely used as starting materials for the synthesis of valuable fuels and chemicals. Herein, we synthesized sub-nanometer (<2nm) Platinum (Pt), Ruthenium (Ru) and Rhodium (Rh) nanoclusters (NCs) via colloidal method; successfully decorated over mesoporous CeO 2 and high surface area (HSA) siliceous meso -cellular foam (MCF 17) and tested for high-pressure CO 2 reduction at lower temperature range (220–340 °C). Pt and Ru NCs exhibited typical reverse water gas shift (RWGS) and methanation catalytic performance respectively with minimal influence of the nature of support however, Rh NCs showed drastic variations in the product selectivity which exhibited strong influence of the support over the product distribution. Furthermore, Ru NCs (with a relatively lower metal loading ∼ 1 wt%) were found to be highly selective to CH 4 (∼99 %) and stable (upto 40 hr time on stream) with either CeO 2 /MCF 17 at 340 °C; also Ru NCs exhibited comparatively the highest CO 2 conversion (∼93 % in case of Ru NCs/CeO 2) among the supported metal NCs. HRTEM results showed that metal NCs were homogeneously dispersed with a controlled and uniform particle size (<2nm); no substantial agglomeration of Ru NCs were observed after reaction. Beside the stable dispersion of NCs, Near Ambient Pressure (NAP) in situ XPS of Ru/CeO 2 showed that the dynamic Ce3+/Ce4+ ratio of CeO 2 can attribute to the high activity and selectivity. [ABSTRACT FROM AUTHOR]