Guijing Li

Nanoporous Ag–CeO2 ribbons prepared by chemical dealloying and their electrocatalytic properties

A novel and facile strategy for the preparation of a monolithic Ag–CeO2 composite is reported. Here, nanoporous Ag–CeO2 ribbons are successfully prepared through dealloying melt-spun Al79.5Ag20Ce0.5 alloy in a 5 wt% NaOH aqueous solution, followed by calcining in air. The Ag–CeO2 ribbons with a homogeneous pore/grain structure are thermally stable up to 973 K because of the formation of Ag cores and CeO2 shells. Uniform CeO2 particles with lengths of about 5 nm are dispersedly loaded on the fine Ag grains of the porous structure. The Raman spectra show that a larger number of oxygen vacancies are formed in the CeO2 nanoparticles with an increase of the calcination temperature. The electrochemical tests reveal that the nanoporous Ag–CeO2 catalyst exhibits an enhanced activity toward the direct oxidation of sodium borohydride. The superior catalytic activity is attributed to the enhancement of the interfacial interaction between Ag and CeO2. The present work opens up a novel method to prepare metal–CeO2 nanocomposites with high catalytic performance and low cost.

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.

NANOPOROUS COPPER–SILICON COMPOSITE PREPARED BY CHEMICAL DEALLOYING AS ANODE MATERIAL FOR LITHIUM-ION BATTERIES

A novel and simple method has been developed to prepare the Cu-Si composite as anode material for lithium-ion batteries. Nanoporous Cu-Si composite with pore sizes of 1~30 nm was prepared by dealloying the melt-spun Al-Cu-Si-Ce ribbons in a 5 wt.% HCl solution. Electrochemical tests revealed that the nanoporous Cu-Si electrodes exhibited highly reversible capacity of 2317 mAhg-1 and retained a capacity of 1030 mAhg-1 over 20 cycles. The excellent electrochemical performance is attributed to the unique porous structure of the Cu-Si composite. Our results demonstrate that this novel composite is a promising anode candidate for high-capacity rechargeable lithium-ion batteries.