Defect-Mediated Gold Substitution Doping in ZnO Mesocrystals and Catalysis in CO Oxidation

Abstract

Highly dispersed supported gold with strong metal–support interaction is a desirable material for heterogeneous catalysis. Unlike current dispersion strategies of depositing gold from solution to support, we report herein a new method of producing highly dispersed gold clusters on ZnO mesocrystal. The gold clusters appeared on defect-rich twin-brush ZnO mesocrystals (TB-ZnO) via an in-and-out process: (i) a mixed Au/Zn oxide was formed first after deposition-precipitation of Au with AuCl4 –, (ii) fine Au clusters grow from the underneath to the surface of the oxide after heating. The TB-ZnO behaved like a sponge allowing gold atoms to heavily disperse into the wurtzite structure of ZnO with Zn-substitution by gold. After mild thermal treatment, the embedded gold emerged from underneath of the ZnO support to form highly dispersed Au nanoparticles of ∼2 nm on the ZnO surface. DFT calculation shows energetically favored Au-doping in TB-ZnO and facile defect-mediated migration of Au in it. The material (Au/TB-ZnO) gave outstanding activities for the catalysis of CO oxidation. The use of mesocrystals of metal oxide as supports, with rich vacancy defects, provides a new route for preparing highly dispersed and active supported metal catalysts.

Highly active and sintering-resistant heteroepitaxy of Au nanoparticles on ZnO nanowires for CO oxidation

“…In addition, from Table 1 we can see that our Au/ZnO NW-600 has similar activity to that of the standard Au/Fe 2 O 3 catalyst (provided by Gold World Council) [47] . It also has similar activity to the previously synthesized Au/ZnO samples calcined at low temperatures except in two cases where the catalysts were prepared by CVD method [48] and the Au clusters supported on defectrich twin-brush ZnO mesocrystals (TB-ZnO) [50] . These results suggest clearly that our Au/ZnO NW-600, even after being calcined at 600 °C, had high activity for CO oxidation.…”

Construction of 2D‐ZnS@ZnO Z‐Scheme Heterostructured Nanosheets with a Highly Ordered ZnO Core and Disordered ZnS Shell for Enhancing Photocatalytic Hydrogen Evolution

“…Figure (b–d) shows the room‐temperature PL spectra of the ZnO and ZnS@ZnO nanosheet. As shown in Figure S6a, the peak at 387 nm can be assigned to the near band edge emission (NBE) of ZnO . The peak centered at about 468 nm can be assigned to the Zn i , which is consistent with that of Zeng et al.…”

The Applications of Morphology Controlled ZnO in Catalysis

“…Its high-resolution electron microscopy images indicated a lot of Au nanocrystals epitaxially oriented on ZnO rods which means the SMSI lead to such a unique structure, and the unique metal-support interactions were proposed to be associated with the enhanced catalytic activity. Recently, Liu et al [141] designed a new method to produce highly dispersed Au clusters on ZnO meso-crystal through a ZnO defect-mediation method. Au clusters were supported on and/or doped in defect-rich twin-brush ZnO (TB-ZnO) meso-crystals (Figure 4), marked as Au/ZnO:Au.…”

“…This is mainly due to the formation of Zn-Mg oxide solid solution in doped ZnO, which leads to a strong metal-support interaction, caused by the electron transfer from the ZnO substrate to Pd NPs, and this SMSI was proved to effectively restrain the sintering of the active Pd NPs, suppressing the growth of Pd NPs, and thus, enhancing the catalytic stability. Reproduced with permission from [141]. Copyright American Chemical Society, 2015.…”

“…The SMSI lead to a large amount of Zn-and O-vacancy defects in TB-ZnO which provides a strong driving force for introducing gold particles into the lattice of ZnO which then eventually move out of ZnO lattice to form highly dispersed Au nanoparticles [141] Mg-ZnO (doping) Flower-like ZnO microspheres Mg 2+ doped ZnO support promotes a strong metal-support interaction caused by the formation of Zn-Mg oxide solid solution, effectively restrain the sintering of the active Pd NPs; retard the growth of Pd NPs, and enhance the catalytic stability [142] Hydro-desulfurization Ni-ZnO Nanowires…”