Reduction Characteristics of Ceria under Ethanol Steam Reforming Conditions: Effect of the Particle Size

Abstract

Reducibility of ceria under steam reforming conditions and the effect of particle size on its reducibility was examined using two ceria samples with distinctly different mean particle sizes (3.5 nm versus 120 nm), but with similar polyhedral morphologies. The degree of reduction from Ce 4+ to Ce 3+ was characterized by temperature programmed reduction (TPR) and in situ X-ray absorption near edge structure spectroscopy (XANES) where the nanopolyhedra were observed to reduce much more readily compared to the larger particle-size sample. There was also significant reduction of the nanopolyhedra under ethanol steam reforming conditions. Ceria nanopolyhedra exhibited significantly more Ce 3+ sites which contributed to a lower occurrence of surface acidic sites. The acidic/basic sites were probed by probe molecules such as pyridine and CO 2 through in situ diffuse reflectance infrared spectroscopy (DRIFTS). The particle size also showed major differences in the steam reforming activity of ceria, with nanopolyhedra with a 3.5-nm mean particle size exhibiting significantly higher carbon cleavage and ethanol dehydration activity than its counterpart of 120 nm mean particle size.

Ambient pressure XPS and IRRAS investigation of ethanol steam reforming on Ni–CeO2(111) catalysts: an in situ study of C–C and O–H bond scission

“…A VG Scienta R4000 HiPP analyzer was used for XPS analysis. 24 The O 1s region was probed with photon energy of 650 eV, and the C 1s, Ni 3p, and Ce 4d 6 regions with photon energy of 490 eV and a resolution of ~0.2 eV. The Ce 4d photoemission lines were used for binding energy calibration based on the 122.8 eV satellite features.…”

Effect of the surface state on the catalytic performance of a Co/CeO2 ethanol steam-reforming catalyst

“…Therefore, the adsorption of ethanol (as ethoxy species) onto metallic particles [30,57] is considered as the initial step of EtOH transformation (1) [31,58]. Ethanol, similarly to other alcohols, also dissociatively adsorbs on ceria [7,[59][60][61]; however, studies of Soykal et al [4,62] and Song et al [16] have shown that bare ceria exhibits rather poor activity in CAC bonds cleavage in temperature range of 400-450°C. Studies of da Silva et al suggest that an EtOH conversion of $50% can be achieved at 500°C with EtOH/H 2 O = 1/3 mol/mol [61,63].…”

Probing the interaction of Rh, Co and bimetallic Rh–Co nanoparticles with the CeO2 support: catalytic materials for alternative energy generation

“…Recently, it was demonstrated that the catalytic performance of CeO 2 depends on the particle size, due to the difference of the reducibility and therefore the number of acidic sites. 37 Depending on the degree of ceria reduction, unique reactivity profiles can also be observed on ceria-supported Rh catalysts. For example, while CO adsorbs non-dissociatively on Rh nanoparticles on fully oxidized ceria films, it dissociates on partially reduced films.…”