This review presents studies and investigations of the use of gold catalysts in environmental applications, from the oxidation of CO and volatile organic compounds (VOCs) in environmental technologies to the production of hydrogen, a non-polluting energy source, in the water-gas shift (WGS) reaction. It summarizes a variety of results, from the discovery made by Haruta et al. about the catalytic behaviour of gold in CO oxidation, to the use of gold-based catalysts in environmental remediation, by the catalytic removal of different types of VOC using a wide variety of oxide supports and finally to the use of this highly active noble metal in WGS applications. It also discusses gold loading methods, comparing them in terms of simplicity, efficiency and the resultant particle size and dispersion of Au over various supports. The application of different types of supporting materials is also presented, with a critical discussion of the parameters affecting the choice and use of such materials, i.e. how the support interacts with gold particles and with pollutant molecules along with the advantages a support offers to VOC oxidation and WGS reactions. It ends by highlighting the potential of gold catalyts in the future.

Co₆Al₂HT hydrotalcite-like compounds were synthesized by three different methods: co-precipitation, microwaves-assisted and ultrasound-assisted methods. The mixed oxides obtained after calcination were studied by several techniques: XRD, TEM, H₂-TPR and XPS. They were also tested as catalysts in the reaction of total oxidation of toluene. The physico-chemical studies revealed a modification of the structural characteristics (surface area, morphology) as well as of the reducibility of the formed mixed oxides. The solid prepared by microwaves-assisted synthesis was the most active. Furthermore, a relationship between the ratio of Co²⁺ on the surface, the reducibility of the Co-Al mixed oxide and the T₅₀ in toluene oxidation was demonstrated. This suggests a Mars Van Krevelen mechanism for toluene total oxidation on these catalysts.

Considering CO2 as a feedstock becomes nowadays more and more of interest. The reutilization of CO2 is already possible via cold plasma techniques operating at atmospheric pressure. One of the promising technologies is the dielectric barrier discharge (DBDs). In most cases they exhibit a low energy efficiency for CO2 conversion. However, several routes can be used to increase this efficiency and hence, the product formation. One of them is the packed-bed DBD configuration with porous beads inside the gap of the DBD, which also allows coupling plasma with catalysis. Catalysts can be introduced in such configuration to exploit the synergistic effect between plasma and catalytically active surfaces, leading to a more efficient process. In this article, the dry reforming of methane (DRM) is studied, which aims to convert both CO2 and CH4, another greenhouse gas, at the same time. The conversions and energy efficiency of the DRM process are investigated and compared in both the packed-bed DBD configurations containing catalysts (Co, Cu or Ni) and the classical DBD. The change in filamentary behavior is studied in detail and correlated with the obtained conversions via gas chromatography, mass spectrometry and using an oscilloscope. A characterization of the catalysts on the beads is also carried out. Both the CO2 and CH4 conversions are clearly increased with the plasma-catalysis. CH4 conversions as high as 90% can be obtained in certain conditions with copper catalysts.