Non‐Thermal Plasma Activation of Gold‐Based Catalysts for Low‐Temperature Water–Gas Shift Catalysis

Abstract

Non‐thermal plasma activation has been used to enable low‐temperature water‐gas shift over a Au/CeZrO4 catalyst. The activity obtained was comparable with that attained by heating the catalyst to 180 °C providing an opportunity for the hydrogen production to be obtained under conditions where the thermodynamic limitations are minimal. Using in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), structural changes associated with the gold nanoparticles in the catalyst have been observed which are not found under thermal activation indicating a weakening of the Au−CO bond and a change in the mechanism of deactivation.

Activation and Deactivation of Gold/Ceria–Zirconia in the Low‐Temperature Water–Gas Shift Reaction

“…When fresh samples of the 2wt% Au/CeZrO 4 catalyst were compared with samples after 48 h on-stream using HAADF-STEM and bright-field transmission electron microscopy (BF-TEM; Figure 2; Supporting Information, Figure S4), 5-10 nm Au particles were found in both, whereas additional particles in the 1-2 nm size range were mostly detected in the used catalyst. [10,11] Figure S5 (Supporting Information) demonstrates that clearly distinguishing atomically dispersed surface Au from substitutional Zr atoms in the CeZrO 4 support is even more challenging.F igure S6 (Supporting Information) shows some representative BF-and HAADF-STEM images of the larger (> 5nm) Au NPs in the fresh and 48 hu sed 2wt% Au/CeZrO 4 catalyst. [10,11] Figure S5 (Supporting Information) demonstrates that clearly distinguishing atomically dispersed surface Au from substitutional Zr atoms in the CeZrO 4 support is even more challenging.F igure S6 (Supporting Information) shows some representative BF-and HAADF-STEM images of the larger (> 5nm) Au NPs in the fresh and 48 hu sed 2wt% Au/CeZrO 4 catalyst.…”

“…Furthermore,X-ray energy-dispersive spectroscopy (XEDS) analysis detected the presence of Au decorating the support where no particles were visible,i mplying the presence of unresolved subnanometer clusters or atomically dispersed Au on the CeZrO 4 surface.T he difficulties in visualizing atomically dispersed Au on CeO 2 using HAADF imaging have been described previously. [10,11] Figure S5 (Supporting Information) demonstrates that clearly distinguishing atomically dispersed surface Au from substitutional Zr atoms in the CeZrO 4 support is even more challenging.F igure S6 (Supporting Information) shows some representative BF-and HAADF-STEM images of the larger (> 5nm) Au NPs in the fresh and 48 hu sed 2wt% Au/CeZrO 4 catalyst. Ac ommon feature noted in the fresh catalyst was that the Au particles were often preferentially located in the three-fold intersection points or in the planar crevices between neighboring CeZrO 4 grains (Supporting Information, Figure S6a).…”

A review on the recent progress, challenges, and perspectives of atmospheric‐pressure cold plasma for preparation of supported metal catalysts

“…They claimed that more charged species were formed with increasing discharge voltage, which prevented the aggregation of Ag NPs. It has been noted that an appropriate discharge voltage (or input power) is necessary as an excessively high input power may accelerate the sintering of metal NPs . For example, AP DBD cold plasma was employed to activate Au/CeZrO 4 catalysts for low‐temperature water‐gas shift catalysis by Stere et al Transmission electron microscopy indicated that the average gold particle size were increased from 0.7 to 1.8 nm after plasma activation.…”

“…The optical emission spectra indicated that copper oxide was not reduced by excited‐state hydrogen atoms or heating effect, and excited‐state hydrogen molecules and hydrogen radicals were proposed to be the reducing agents . Hydrogen radicals were also deemed to be the reducing agents when using sonochemical deposition method and hot‐wire method for metal ions reduction.…”

Efficient catalytic hydrogen generation by intermetallic platinum-lead nanostructures with highly tunable porous feature

“…The main target of the WGS reaction is to remove the carbon monoxide (CO) formed during the upstream hydrocarbon reforming reaction to increase the H 2 yield as well as the H 2 purity. This step is essential since CO is often a poison for downstream processing catalysts, resulting in large activity decrease [3]. In industrial fields, the common systems contain a high temperature shift over Fe-Cr catalysts at 593-723 K and a low temperature shift over Cu-Zn-Al catalysts at 473-523 K [4].…”