A Rapid and Efficient Method to Deposit Gold Particles onto Catalyst Supports and Its Application for CO Oxidation at Low Temperatures

Abstract

A rapid, simple, and efficient method for the preparation of highly dispersed supported Au catalysts has been developed. In the preparation, NaBH4 is used to reduce the Au precursor, lysine is employed to cap the formed Au colloids, and a short sonication time is applied to facilitate dispersion and deposition of the Au colloids onto the catalyst support, which has been mixed with the precursor beforehand. The end‐point pH value of the solution and the isoelectric points (IEPs) of the catalyst supports have an influence on the size of the Au particles and their deposition. The optimum value for the end‐point pH is 7.5–10.0, and the IEP should be 5–10. The amino acid capping agent is easily removed at the catalyst activation stage at 200 °C, and the Au particles are thermally stable against sintering, even at 500 °C for 3 h. It is also proven that the method is applicable to the preparation of supported Pt catalysts. The catalytic activity of the prepared Au catalysts for CO oxidation in the absence/presence of H2 is comparable to that of a Au catalyst prepared by the co‐precipitation (CP) method, and to that of the standard catalyst from the World Gold Council (WGC). X‐ray photoelectron spectroscopy (XPS) results show that only metallic Au exists in the catalysts before and after activation, and also after the catalysis reaction.

Correlation of the Catalytic Activity for Oxidation Taking Place on Various TiO2 Surfaces with Surface OH Groups and Surface Oxygen Vacancies

“…The suspension was then washed four times with DI water and centrifugation was carried out before drying at 60 8C overnight and calcining at 300 8C for 1 h. This method can lead to a nearly complete gold precipitation from the gold precursor solution as proven in our previous report. [36] Catalytic activity test-HCHO oxidation: The Au/TiO 2 catalysts (20 mg) were suspended in ethanol (0.5 mL) to coat the solid onto a glass plate (7 cm in diameter), which was then dried at 80 8C. The coated plate was placed in a 6 L glass vessel located in a chamber equipped with six 18 W light tubes (Philips, TLD18, wavelength 400-500 nm) as the light source.…”

Chemical Preparation of Supported Bimetallic Catalysts. Gold-Based Bimetallic, a Case Study

“…However, sintering can be prevented using a SA that decomposes at low temperature. This holds for lysine, which can decompose at 200˝C without growth of the particles (<5 nm) supported on α-Fe 2 O 3 [54]. Alternatively, ozone treatment or plasma activation can be used, both performed at RT.…”

Ultrafine Magnetite Nanopowder: Synthesis, Characterization, and Preliminary Use as Filler of Polymethylmethacrylate Nanocomposites

“…In particular, nanosized oxide materials such as magnetite (Fe 3 O 4 ), maghemite (γ-Fe 2 O 3 ), and hematite (α-Fe 2 O 3 ) have found wide-ranging applications. Hematite nanoparticles, crystallizing in the rhombohedral system and showing a weak ferromagnetic behavior at room temperature [1], have been extensively used as catalyst [2,3], pigment [4], gas sensor [5], optical devices [6], and medicine applications [7]. Magnetite and maghemite, instead, crystallizing in the cubic crystal system and with a ferromagnetic behavior at room temperature, have been widely exploited in technological applications including information storage [8], sensors [9], refrigeration [10], and coil cores [11], as well as in contrast agent for magnetic resonance imaging [12,13], and potential mediator for magnetic hyperthermia [14].…”