Xiaolong Zhang

Baize-like CeO2 and NiO/CeO2 nanorod catalysts prepared by dealloying for CO oxidation

Baize-like monolithic CeO2 and NiO/CeO2 nanorod catalysts were prepared by combined dealloying and calcination and the catalytic activities were evaluated using CO catalytic oxidation. The CeO2 catalysts were composed of nanorods and exhibited a three-dimensional supporting structure with pores. After introduction of NiO, dispersed NiO nanosheets and nanoparticles were supported on the surface of CeO2 nanorods and they were not well-crystallined due to CeO2 inhibiting the NiO crystallization. The Raman and x-ray photoelectron spectroscopy analyses revealed that the introduction of NiO species into CeO2 generated more coordinate unsaturated Ni atoms, oxygen vacancies, defects and active sites for CO catalytic reactions. The reaction activation energy of NiO/CeO2 nanorod catalyst prepared from the Al83Ce10Ni7 precursor alloy was just 31.2 kJ mol-1 and the CO conversion can reach up to 97% at 240 °C, which was superior to that of pure CeO2 and nanoporous NiO. The enhanced catalytic activity of baize-like NiO/CeO2 nanorods can be attributed to the strong synergistic effects between finely dispersed NiO species and surface oxygen vacancies in CeO2 nanorods.

Monolithic Au/CeO2 nanorod framework catalyst prepared by dealloying for low-temperature CO oxidation

Monolithic Au/CeO2 nanorod frameworks (NFs) with porous structure were prepared by dealloying melt-spun Al89.7Ce10Au0.3 ribbons. After calcination in O2, a 3D Au/CeO2 NF catalyst with large surface area was obtained and used for low-temperature CO oxidation. The small Au clusters/nanoparticles (NPs) were in situ supported and highly dispersed on the nanorod surface, creating many nanoscale contact interfaces. XPS results demonstrated that high-concentration oxygen vacancy and Au δ+/Au0 co-existed in the calcined sample. The Au/CeO2 nanorod catalyst calcined at 400 °C exhibited much higher catalytic activity for CO oxidation compared with the dealloyed sample and bare CeO2 nanorods. Moreover, its complete reaction temperature was as low as 91 °C. The designed Au/CeO2 NF catalyst not only possessed extreme sintering resistance but also exhibited high performance owing to the enhanced interaction between the Au clusters/NPs and CeO2 nanorod during calcination.

Three-dimensional architecture of Ag/CeO2 nanorod composites prepared by dealloying and their electrocatalytic performance

A novel three-dimensional (3D) architecture of Ag/CeO2 nanorods with high electrocatalytic activity was prepared by dealloying melt-spun Al–Ag–Ce alloys in NaOH aqueous solutions for NaBH4 electro-oxidation. The nanorod composite was composed of CeO2 nanorods and large-size Ag nanoparticles. After undergoing calcination at 573 K in air, many highly dispersed small Ag nanoparticles were generated and deposited on the surface of the CeO2 nanorod framework. Well-defined Ag/CeO2 interfaces were created via the anchoring of small Ag nanoparticles on the CeO2 nanorods, and the nanorods were connected by larger conductive Ag nanoparticles. Electrochemical measurements showed that the mass specific current of the Ag/CeO2 composites was 2.5 times higher than that of pure Ag for BH4− oxidation. The Ag/CeO2 composites exhibited enhanced catalytic activity owing to the 3D nanorod architecture, strong interfacial interactions between small Ag nanoparticles and CeO2 nanorods, and high concentrations of surface oxygen species.

CeO 2 Nanorod-Supported Transition Metal Catalysts Prepared by Dealloying for CO Oxidation

In this study, Al–Ce, Al–Ce–Ni, and Al–Ce–Mn precursor alloys were prepared by melt-spinning, and then dealloyed in 20% NaOH aqueous solution and calcined in air. The catalytic activities of the as-prepared precursors were evaluated for the oxidation of CO at atmospheric pressure. The results revealed that a novel CeO2 nanorod-supported skeleton structure could be obtained by dealloying and calcining the as-quenched Al–Ce ribbons. The CO conversion temperatures for the CeO2/NiO and CeO2/MnO2 composites were reduced to about 147 and 136 °C, respectively, which indicated the superior activity of these composites as compared to pure CeO2 (Zhang et al. in Nanotechnology 28, 45602, 2017) [11]. The reason for the increased catalytic performance can be attributed to the large number of active sites provided by the composite materials. The synergistic effects at the NiO/MnO2 and CeO2 interface as well as the increase in the concentration of oxygen vacancies in the composites also play important roles in the enhancement of the catalytic performance.