Effect of Nickel Oxide Doping to Ceria-Supported Gold Catalyst for CO Oxidation and Water-Gas Shift Reactions

Miao Shu,Chun-Jiang Jia,Shuai Wei,Rui Si,Dao-Lei Wang

doi:10.3390/catal8120584

Abstract

Ceria-supported gold catalyst has drew much research interest owing to its high reactivity on CO oxidation and water-gas shift (WGS) reactions. However, till now, there were relatively limited studies on the effect of secondary metal/metal oxide component into gold-ceria system to enhance its catalytic performance. In this work, we synthetized the ceria supported gold-nickel samples via a deposition-precipitation method with the base of NaHCO3 to adjust final pH value of 8~9. We found that the addition of nickel oxide drove off the gold species from the stock solution during synthesis, and thus resulted in a dramatical decrease on doped Au concentration. No crystallized phases of gold and nickel were observed on the surface of ceria nanorods in both X-ray diffraction (XRD) and transmission electron microscopy (TEM). The valence of nickel was maintained as Ni2+ for all the measured samples by X-ray photoelectron spectroscopy (XPS), while gold was oxidized with the increased nickel amount after analysis of X-ray absorption near edge spectroscopy (XANES). The corresponding catalytic tests showed that with the introduction of nickel oxide, the activity of gold-ceria catalyst was promoted for the WGS reaction, but inhibited for the CO oxidation reaction.

Highlights

There are considerable research have ascertained that supported metal catalysts, especially to gold catalysts, are extraordinarily active for oxidation of carbon monoxide (2CO + O2 = 2CO2 ) [1,2,3,4,5,6] and water-gas shift (CO + H2 O = CO2 + H2 ) [7,8,9,10,11,12] reaction
We investigated three different precipitating agents: ammonium carbonate ((NH4 )2 CO3 ), sodium carbonate (Na2 CO3 ) and sodium hydrogen carbonate (NaHCO3 ), and found that: (1) (NH4 )2 CO3 is very suitable for gold deposition onto pure ceria [7], but nickel ion was complexed with molecular ammonia, which is prejudicial to the deposition of nickel; (2) When
We hypothesized that the as-formed Ni(OH)x(H2O)y nucleation in stock solution can cover part of ceria ceria-supported pure gold (AuCe) and gold-nickel (AuNiCe) samples, respectively

Summary

Introduction

There are considerable research have ascertained that supported metal catalysts, especially to gold catalysts, are extraordinarily active for oxidation of carbon monoxide (2CO + O2 = 2CO2 ) [1,2,3,4,5,6] and water-gas shift (CO + H2 O = CO2 + H2 ) [7,8,9,10,11,12] reaction. Carrettin et al reported that nanocrystalline CeO2 supported gold nanoparticles are more active than those anchored on other oxides (TiO2 , Fe2 O3 ) for CO oxidation [1]. Fu et al confirmed that gold nanoparticles are essential for some oxidation reactions, but unimportant in WGS reaction over Au-ceria [22]. On the basis of these findings, we can see the significant importance of physical and chemical properties of Au modified by the matrix

Objectives

Methods

Results

Discussion

Conclusion