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Abstract: The influence of adsorbed sulfide (S2− ads) on CO monolayer electro-oxidation reaction (CMOR with M for monolayer to emphasize that oxidation always starts with a saturated CO coverage) on carbon-supported Pt nanoparticles (Pt/C NPs) was investigated using electrochemical and in situ ATR-SEIRAS (attenuated total reflection-surface enhanced IR absorption spectroscopy) techniques. An enhanced kinetics of CMOR on the S2− ads-Pt/C was observed by potentiodynamic CO stripping and potentiostatic CO oxidation analyses. Electrochemical impedance measurements revealed a weakened bonding of oxygen-containing species with the S2− ads-Pt/C surface as compared with the clean Pt/C surface, which we believe was the main reason for the observed enhanced CMOR by the S2− ads. The in situ SEIRAS data showed the existence of both linear- and bridge-bonded CO (COL and COB respectively) in all samples and that the sulfide adsorption increased substantially the fraction of the former on the available Pt sites and facilitated the conversion between them. Our results also indicate that the frequently observed pre-CMOR current arises most likely from oxidation of weakly-bonded CO rather than from reactions taking place at defect sites. [Copyright &y& Elsevier]

Abstract: The CO2 capture properties of a new nanocrystalline CaO-based mixed oxide (CaCeZrO x ) were studied in both TGA and a fixed bed reactor. The kinetics of CO2 capture at dry conditions was compared between these two reactors. The application of the new CO2 acceptor in sorption enhanced steam methane reforming was studied by a fixed-bed reactor in the presence of 40wt% nickel hydrotalcite catalysts. Experimental results show that the new CO2 acceptor, CaCeZrO x has a significantly improved CO2 capture capacity and cyclic reaction stability compared to natural dolomites, because of the large pores and stable backbone structure. It has also been observed that the sorption enhanced steam methane reforming in the fixed bed reactor produces more than 95% H2 in a single-step process. Increase in production of hydrogen and higher CO2 capture capacity are also observed with an increase in the residence time of methane. Steam has a significant effect on the stability of the acceptors, but not very much on the kinetics and capacity of CO2 capture. The capacity of CO2 capture on the acceptors in the SESMR process cannot be predicted by the independent CO2 capture kinetic study on acceptor alone. A synergy effect between the sorption enhanced reactions and CO2 capture on the CO2 capture capacity was observed on the all solid CaO based CO2 acceptors. [Copyright &y& Elsevier]

Abstract: First-principles calculations based on density functional theory (DFT) have been used to investigate the reaction mechanism of dry methane reforming on Ni(111). The most energetically favorable adsorption configurations of the species involved in this process are identified and the transition states for all the possible elementary steps are explored by the dimer method. Then, the related thermodynamic properties at 973.15K are calculated by including the zero-point energy correction, thermal energy correction and entropic effect. It is found that CO2 dissociates via a direct pathway to produce CO and O dominantly, and atomic O is revealed to be the primary oxidant of CH x intermediates. Based on this information, two dominant reaction pathways are constructed as both the CH and C oxidation are found to be likely. The reaction network begins with the dissociation of CO2 and CH4, and then the generated CH and C are oxidized by atomic O to produce CHO and CO, followed by the CHO decomposition to finally generate CO and H2. As for these two reaction pathways, the oxidation step is predicted to determine the overall reaction rate under the current investigated conditions, while the CH4 dissociation is found to be the rate-limiting step at lower temperatures. [Copyright &y& Elsevier]

[Display omitted] • Polyethylenimine over mesoporous carbon spheres solid sorbent for CO 2 capture. • CO 2 capture capacity (3.22 mmol/g) was achieved on 62.5PEI/MCS-1.1. • PEI /MCS will be one of the ideal candidates for CO 2 capture in the future. A novel low-concentration CO 2 capture material (PEI/MCS) was developed by loading polyethylenimine (PEI) over mesoporous carbon spheres (MCS) with high porosity. The effects of pore structure, PEI loading, capture temperature, and promoters on CO 2 capture of PEI/MCS were studied. The MCS with perfect spherical morphology was successfully synthesized by a hard-template assisted reverse emulsion method. The pore structure of MCS was adjusted by tuning the ratio of silica to carbon (Si/C) in the precursors. With increasing the Si/C from 0.8 to 1.1, the pore volume of MCS increased from 1.25 to 2.68 cm3/g. The optimal PEI loadings depending on the pore volume of MCS were 45, 62.5, and 65 wt.% for MCS-0.8, MCS-1.1, and MCS-1.5, respectively. The highest CO 2 capture capacity (3.22 mmol/g) was achieved on 62.5PEI/MCS-1.1 at CO 2 partial pressure of 0.05 bar (5 vol.%, a typical concentration of the tail gas from natural gas power plant and natural gas processing plant) and temperature of 75 °C, outperforming most of the solid amine sorbents reported at similar condition. However, the cycling stability of PEI/MCS is poor at the capture-regeneration temperature of 75 °C. The promoters Span 80 and 1,2-epoxybutane did not show remarkable effect on the cycling stability of PEI/MCS at 75 °C. Decreasing the capture-regeneration temperature can significantly improve the stability of PEI/MCS and there is almost no CO 2 capacity loss (regeneration >99.5 %) when the temperature decreased to 50 °C. As a result of high CO 2 capacity and excellent regenerability and stability, PEI /MCS will be one of the ideal candidates for CO 2 capture in the future. [ABSTRACT FROM AUTHOR]

Nanocrystalline ZnO/CNT with enhanced electrochemical reduction of CO 2 to syngas [Display omitted] • Faradaic efficiency of synthesis gas of more than 75% was achieved on small ZnO particles. • The H 2 /CO ratio can be tailored by the ZnO particle size. • DFT study revealed the ZnO surface stabilizes CO 2 * and COOH* intermediates, therefore more active for CO 2 activation. • ZnO is promising for electrochemical syngas production. Electrochemical reduction of CO 2 and H 2 O can provide a promising pathway to synthesis gas generation for renewable electric energy storage and fuel production with the closed anthropogenic carbon cycle. However, the lack of affordable highly active catalysts to activate the stable CO 2 and H 2 O molecules presents a substantial challenge. Here we report ZnO supported on nanocarbon as a cost-effective and active catalyst for selective conversion of CO 2 and H 2 O to predominately synthesis gas, with higher selectivity and activity compared to polycrystalline metal catalysts such as Ag and Cu. The H 2 /CO ratio can be tailored for different industrial processes by tuning the applied potential and the particle size of ZnO. Density functional theory calculations showed that the higher activity of ZnO is related to more significantly stabilized intermediates, CO 2 *, COOH, and CO* compared to Cu and Ag. Our results highlight a promising class of low-cost, abundant oxide as active electrocatalysts for synthetic fuel production from CO 2. [ABSTRACT FROM AUTHOR]