Rare earth oxides and their supported noble metals in application of environmental catalysis

Volatile organic compounds(VOCs),methane,carbon monoxide,soot,automotive exhaust,and nitrogen oxides are harmful to the atmosphere and human health.It is urgent to strictly control their emissions.Heterogeneous catalysis is an effective pathway for the removal of these pollutants,and the critical issue is the development of novel and high-performance catalysts.In this review,we briefly summarize the preparation methods,physicochemical properties,catalytic activities,and related reaction mechanisms for the above pollutants removal of the rare earth oxides,mixed rare earth oxide,rare earth oxidesupported noble metal,and mixed rare earth oxide-supported noble metal catalysts that have been investigated by our group and other researchers.It was found that catalytic performance was associated with the factors,such as specific surface area,pore structure,particle size and dispersion,adsorbed oxygen species concentration,reducibility,reactant activation ability or interaction between metal nanoparticles and support.Furthermore,we also envision the development trend of such a topic in future work.

Au-Pd/mesoporous Fe_2O_3:Highly active photocatalysts for the visible-light-driven degradation of acetone

Three-dimensionally ordered mesoporous Fe2O3（meso-Fe2O3） and its supported Au, Pd,and Au-Pd alloy（xA uP dy/meso-Fe2O3; x = 0.08–0.72 wt.%; Pd/Au molar ratio（y） = 1.48–1.85）photocatalysts have been prepared via the KIT-6-templating and polyvinyl alcohol-protected reduction routes, respectively. Physical properties of the samples were characterized, and their photocatalytic activities were evaluated for the photocatalytic oxidation of acetone in the presence of a small amount of H2O2 under visible-light illumination. It was found that the meso-Fe2O3 was rhombohedral in crystal structure. The as-obtained samples displayed a high surface area of 111.0–140.8 m^2/g and a bandgap energy of 1.98–2.12 eV. The Au, Pd and/or Au–Pd alloy nanoparticles（NPs） with a size of 3–4 nm were uniformly dispersed on the surface of the meso-Fe2O3 support. The 0.72 wt.% AuP d1.48/meso-Fe2O3 sample performed the best in the presence of 0.06 mol/L H2O2 aqueous solution, showing a 100% acetone conversion within4 hr of visible-light illumination. It was concluded that the good performance of 0.72 wt.%AuPd（1.48）/meso-Fe2O3 for photocatalytic acetone oxidation was associated with its ordered mesoporous structure, high adsorbed oxygen species concentration, plasmonic resonance effect between AuPd（1.48） NPs and meso-Fe2O3, and effective separation of the photogenerated charge carriers. In addition, the introduction of H2O2 and the involvement of the photo-Fenton process also played important roles in enhancing the photocatalytic activity of 0.72 wt.%AuPd（1.48）/meso-Fe2O3.