Shape-Controlled Pathways in the Hydrogen Production from Ethanol Steam Reforming over Ceria Nanoparticles

Abstract

The ethanol surface reaction over CeO 2 nanooctahedra (NO) and nanocubes (NC), which mainly expose (111) and (100) surfaces, respectively, was studied by means of infrared spectroscopy (TPSR-IR), mass spectrometry (TPSR-MS), and density functional theory (DFT) calculations. TPSR-MS results show that the production of H 2 is 2.4 times higher on CeO 2 -NC than on CeO 2 -NO, which is rationalized starting from the different types of adsorbed ethoxy species controlled by the shape of the ceria particles. Over the CeO 2 (111) surface, monodentate type I and II ethoxy species with the alkyl chain perpendicular or parallel to the surface, respectively, were identified. Meanwhile, on the CeO 2 (100) surface, bidentate and monodentate type III ethoxy species on the checkerboard O-terminated surface and on a pyramid of the reconstructed (100) surface, respectively, are found. The more labile surface ethoxy species on each ceria nanoshape, which are the monodentate type I or III ethoxy on CeO 2 -NO and CeO 2 -NC, respectively, react on the surface to give acetate species that decompose to CO 2 and CH 4 , while H 2 is formed via the recombination of hydroxyl species. In addition, the more stable monodentate type II and bidentate ethoxy species on CeO 2 -NO and CeO 2 -NC, respectively, give an ethylenedioxy intermediate, the binding of which is facet-dependent. On the (111) facet, the less strongly bound ethylenedioxy desorbs as ethylene, whereas on the (100) facet, the more strongly bound intermediate also produces CO 2 and H 2 via formate species. Thus, on the (100) facet, an additional pathway toward H 2 formation is found. ESR activity measurements show an enhanced H 2 production on the nanocubes.

Mechanistic insights into CeO2-catalyzed direct synthesis of diethyl carbonate from CO2 and ethanol assisted by zeolite and 2,2-diethoxypropane

“…As above, EtOH is readily adsorbed onto the CeO 2 surface to form ethoxy species, 46 which could react with CO 2 to produce ethyl carbonate species. To confirm this mechanism, we initially conducted DRIFT spectroscopy for the CeO 2 surface that was exposed to EtOH and/or CO 2 at room temperature (Fig.…”

“…This reaction order indicates that EtOH molecules do not affect the rate-determining step of DEC formation and rather suggests that the surface of the CeO 2 catalyst is saturated readily by EtOH and such adspecies decide the reaction rate. Indeed, the chemisorption of EtOH onto the CeO 2 surface was reported to readily occur, 46 and we also examined the adsorption state of EtOH by DRIFT spectroscopy (see section 3.4). On the other hand, in the presence of DEP and H-FAU, the reaction order with respect to EtOH concentration was changed to 0.58 (Fig.…”

“…S12 †), consistent with a previous report. 46 The pressurization with CO 2 altered the spectrum from (b) to (e). The absorption bands at 1342, 1381, 1485, and 1574 cm −1 indicated the formation of ethyl carbonate species on the CeO 2 surface.…”

Interface of Ni-MgCr2O4 Spinel Promotes the Autothermal Reforming of Acetic Acid through Accelerated Oxidation of Carbon-Containing Intermediate Species

“…Hydrogen, as one of the prospective energy carriers, is expected to play an important role in on-board automobile applications; however, ∼95% of H 2 is currently produced via fossil resources of natural gas, coal, and naphtha, accompanied by corresponding carbon emission. , In contrast, biomass, as a carbon-neutral material with high availability, is an abundant resource for hydrogen production. − Based on fast pyrolysis, biomass can be easily converted to bio-oil, consisting of oil and aqueous phases, and value-added chemicals can be reclaimed in the oil phase, while the aqueous phase contains acetic acid (HAc) with content up to 30 wt % and thus presents a cheap and alternative feedstock for green H 2 production. , …”

“…To date, two strategies are mainly used to prevent carbon deposition: (1) to react with the as-formed coke species, and…”