Design of an ultrasmall Au nanocluster–CeO2 mesoporous nanocomposite catalyst for nitrobenzene reduction

Abstract

In this work we are inspired to explore gold nanoclusters supported on mesoporous CeO2 nanospheres as nanocatalysts for the reduction of nitrobenzene. Ultrasmall Au nanoclusters (NCs) and mesoporous CeO2 nanospheres were readily synthesized and well characterized. Due to their ultrasmall size, the as-prepared Au clusters can be easily absorbed into the mesopores of the mesoporous CeO2 nanospheres. Owing to the unique mesoporous structure of the CeO2 support, Au nanoclusters in the Au@CeO2 may effectively prevent the aggregation which usually results in a rapid decay of the catalytic activity. It is notable that the ultrasmall gold nanoclusters possess uniform size distribution and good dispersibility on the mesoporous CeO2 supports. Compared to other catalyst systems with different oxide supports, the as-prepared Au nanocluster-CeO2 nanocomposite nanocatalysts showed efficient catalytic performance in transforming nitrobenzene into azoxybenzene. In addition, a plausible mechanism was deeply investigated to explain the transforming process. Au@CeO2 exhibited efficient catalytic activity for reduction of nitrobenzene. This strategy may be easily extended to fabricate many other heterogeneous catalysts including ultrasmall metal nanoclusters and mesoporous oxides.

Mesoporous TiO2 nanofibers with controllable Au loadings for catalytic reduction of 4-nitrophenol

“…Au NPs are usually loaded on various supporting materials, such as polymer [7,8], reduced graphene oxide (RGO) [9], silica [10], carbon nanotubes (CNT) [11], metal oxides [12,13], to prevent coalesce, agglomeration, particle growth, and consequently a decrease in catalytic activity. Among them, the incorporation of Au NPs in mesoporous metal oxide supports provides a convincing strategy to hybrid heterogeneous catalysts for chemical transformation [14][15][16][17]. The mesoporous channels in metal oxide supports offer larger surface area, to minimize diffusion barriers, and potentially enhance the distribution of active sites [18,19].…”

CeO2-encapsulated noble metal nanocatalysts: enhanced activity and stability for catalytic application

“…With the development of synthetic techniques in nanoscience, small noble metal NPs, especially atomically precise nanoclusters/metal oxide hybrid nanostructures, have been successfully fabricated very recently, and these materials exhibit remarkable enhanced catalytic activity and selectivity. [21][22][23] However, this simple loading form cannot meet the growing demand for the stability, because the noble metal catalysts contain numerous exposed surfaces and are always used in harsh environments, such as those with high temperatures and concentrated acid and alkali solutions. The lack of surface protection causes the noble metal NPs to easily aggregate to minimize the surface energy, which can cause a serious loss of the catalytic active sites, a reduction of the catalytic activity and even complete inactivation (as shown in Scheme 1).…”

“…With the development of synthetic techniques in nanoscience, small noble metal NPs, especially atomically precise nanoclusters/metal oxide hybrid nanostructures, have been successfully fabricated very recently, and these materials exhibit remarkable enhanced catalytic activity and selectivity. [21][22][23] However, this simple loading form cannot meet the growing demand for the stability, because the noble metal catalysts contain numerous exposed surfaces …”

Preparation of platinum nanoparticles immobilized on ordered mesoporous Co3O4–CeO2 composites and their enhanced catalytic activity

“…21,22 For example, Chong et al reported Au nanoclusters were deposited on mesoporous ceria nanospheres, exhibiting efficient catalytic reduction of nitrobenzene compared to catalyst systems with silica or ferric oxide supports. 23 Our previous investigation showed Pt NPs supported on ordered mesoporous ceria exhibited better catalytic performance compared to the common ceria support system. 24 With the developing of compound materials in recent years, more attention was paid to the fabrication of mesoporous ceria oxide doped by other metal oxides, which could improve catalytic activity owing to the formation of heterojunctions.…”