Controlled selectivity for ethanol steam reforming reaction over doped CeO2 surfaces: The role of gallium

Abstract

The ethanol steam reforming reaction, together with the adsorption and decomposition of ethanol was studied on CeO 2 and gallium-doped ceria (CeGaO x) by a combined experimental and theoretical approach using infrared spectroscopy (IR), mass spectrometry (MS) and density functional theory (DFT) calculations. At 100°C, different types of monodentate ethoxy species were identified as standing-up (SU) on Ce 4+ and lying-down (LD) on Ce 4+ and Ga 3+ , with the alkyl chain more perpendicular or parallel to the surface, respectively. It is suggested that the incorporation of Ga into the ceria lattice changes the decomposition pathway of LD species, which converts to acetate instead of ethylene, attributed to the increased lattice oxygen lability in the CeOGa interface upon doping and the propensity to form GaH surface species. Under ethanol steam reforming conditions, Ga doping of ceriabased materials has a drastic effect by improving the H 2 :CO 2 ratio, changing the product distribution and reducing coke formation.

Main Hydrogen Production Processes: An Overview

“…Moreover, sodium promotes C-C scission. Ga doping of ceria-based catalysts improves the H 2 /CO 2 ratio in ESR reaction, by changing the product distribution and reducing the coke formation [48]. The stability of Co/CeO 2 and Ni/CeO 2 catalysts have been improved by the La 2 O 3 promoter, the carbon formation rate has been reduced as results of an increased active phase dispersion and a strengthening of the metal-support interactions [49].…”

Comparative studies of metal‐organic decomposed GaxCeyOz and CeO2 based functional MOS capacitor

“…To‐date, the wide band gap gallium oxide (Ga 2 O 3 ) has achieved considerable attraction, owing to its versatility as a passivation layer for AlGaN/GaN MOS high‐electron‐mobility transistors (HEMT), 8,9 Si solar cells, 10 InGaN light‐emitting diode, 11 solar‐blind ultraviolet detectors, 12 window layer for optoelectronic devices, and water splitting 13 . Literatures have reported the aspects of generating higher amount of oxygen vacancies in the doped CeO 2 as well as enhanced redox activities yet the findings with regard to high‐ k MOS application remains rare 14 . The wide band gap (4.4‐4.9 eV) and moderate k value (10) of Ga 2 O 3 8,9,15 coupled with CeO 2 are anticipated to yield a wider tunability in term of k and band gap, leading to the formation of Ga 3+ doped CeO 2 with improved MOS characteristics, which have not been explored thus far.…”

“…13 Literatures have reported the aspects of generating higher amount of oxygen vacancies in the doped CeO 2 as well as enhanced redox activities yet the findings with regard to high-k MOS application remains rare. 14 The wide band gap (4.4-4.9 eV) and moderate k value (10)…”

Growth of metal‐organic decomposed ternary Ga x Ce y O z films by nitrogen‐infused wet oxidation for metal‐oxide‐semiconductor capacitor

“…The efforts of doping Ga 3+ into CeO 2 have been initiated, and findings divulged that the interaction of Ga with CeO 2 would weaken the Ce--O bonds, and thus providing a higher number of actives sites for enhancement of the catalytic behaviour. 20 Besides, the introduction of Ga 3+ to CeO 2 lattice would generate negative oxide charges, which would thus compensate for effective positive oxide charges commonly present in high k oxides. 33 Nonetheless, the details were not specified and the relevant investigation on employing Ga 3+ doped CeO 2 to passivate MOS devices is not present.…”

“…To date, previous literature has reported the synthesis of bulk Ga x Ce y O z material for controlled selectivity over ethanol steam reforming reaction, 20 hydrogen purification for fuel cells, 23 and hydrogenation of acetylene. 34 The investigation of the Ga x Ce y O z material as a high k passivation layer is meagre and thus far, only one study was reported.…”