RT journal article
T1 Insights on hydride formation over cerium-gallium mixed oxides: A mechanistic study for efficient H2 dissociation
A1 Vecchietti, Julia
A1 Baltanas, Miguel A.
A1 Gervais, Christel
A1 Collins, Sebastian E.
A1 Blanco Montilla, Ginesa
A1 Matz, Olivier
A1 Calatayud, Mónica
A1 Bonivardi, Adrián
A2 Ciencia de los Materiales e Ingeniería Metalúrgica y Química Inorgánica
AB A four-step reaction mechanism is proposed for the H2 dissociation over pure ceria and galliumpromoted mixed oxide materials, in a combined experimental and computational investigation. Twosamples of cerium-gallium mixed oxides with Ce/Ga atomic ratios equal to 90/10 and 80/20 were studiedby time-resolved diffuse reflectance infrared spectroscopy under H2 (D2) flow at isothermal condition inthe range of 523–623 K. X-ray photoelectron spectrometry allowed to conclude that only Ce4+ is reducedto Ce3+ (Ga3+ is not reduced), in agreement with density functional theory (DFT) results. The time evolution profiles of gallium hydride ðGaAHÞ species, hydroxyl groups (OH) and Ce3+ infrared signals were analyzed and kinetic rate parameters for each step were obtained by mathematical modeling. The values foractivation energies were in agreement with those calculated by DFT, for the different elementary pathways. A small activation energy (4 kcal/mol) was found for H2 dissociation found on Ga  OACe sitesassuming that the heterolytic cleavage of the HAH bond is the rate determining step. On pure ceria,the experimental activation energy is 23 kcal/mol, showing that the addition of Ga3+ cations booststhe splitting of H2. Interestingly, the reduction step of pure CeO2 surface domains seems to proceed viaa CeH/OH pair intermediate, according to DFT calculations. Moreover, 71Ga NMR experiments indicatethe possible presence of gallia nanodomains. It is proposed that the generation of Ga  OACe sites inthe perimeter of such surface gallia nanodomains is responsible for the enhanced reactivity of the mixedmaterials. The key role of this new type of sites to improve the efficiency of relevant catalytic reactionssuch as selective alkyne hydrogenation and light alkane dehydrogenation is then analyzed.
PB Academic Press Inc.
SN 1090-2694
YR 2017
FD 2017
LK http://hdl.handle.net/10498/35512
UL http://hdl.handle.net/10498/35512
LA eng
DS Repositorio Institucional de la Universidad de Cádiz
RD 21-sep-2026