Synthesis of Au–Ag Alloy Nanoparticle-Incorporated AgBr Crystals

Recent advances and mechanism of plasmonic metal-semiconductor photocatalysis

Benefiting from the unique surface plasmon properties, plasmonic metal nanoparticles can convert light energy into chemical energy, which is considered as a potential technique for enhancing plasmon-induced semiconductor photocatalytic reactions. Due to the shortcomings of large bandgap and high carrier recombination rate of semiconductors, their applications are limited in the field of sustainable and clean energy sources. Different forms of plasmonic nanoparticles have been reported to improve the photocatalytic reactions of adjacent semiconductors, such as water splitting, carbon dioxide reduction, and organic pollutant degradation. Although there are various reports on plasmonic metal-semiconductor photocatalysis, the related mechanism and frontier progress still need to be further explored. This review provides a brief explanation of the four main mechanisms of plasmonic metal-semiconductor photocatalysis, namely, (i) enhanced local electromagnetic field, (ii) light scattering, (iii) plasmon-induced hot carrier injection and (iv) plasmon-induced resonance energy transfer; some related typical frontier applications are also discussed. The study on the mechanism of plasmonic semiconductor complexes will be favourable to develop a new high-performance semiconductor photocatalysis technology.

Activity of Ag/CeZrO2, Ag+K/CeZrO2, and Ag-Au+K/CeZrO2 Systems for Lean Burn Exhaust Clean-Up

Herein, the activity of Ag and bimetallic Au-Ag catalysts, supported over Ce0.85Zr0.15O2 (CZ), was investigated in a complex stream, whose components included CO, C3H8, NO, O2, and, optionally, an injection of water vapor. In such a stream, three of the possible reactions that can occur are CO oxidation, propane combustion, and NO oxidation. The aim of these studies was to explore whether silver, due to its strong affinity to oxygen, will counteract the stabilization of oxygen by potassium. The effect of the presence of potassium ions on the activity of the monometallic silver catalysts is beneficial in the complex stream without water vapor in all three studied reactions, although it is negligible in the model CO stream. It has been shown that water vapor strongly suppresses the activity of the Ag+K/CZ catalyst, much more so than that of the Ag/CZ catalyst. The second purpose of the work was to determine whether the negative effect of potassium ions on the activity of nanogold catalyst can be countered by the addition of silver. Studies in a model stream for CO oxidation have shown that, for a catalyst preloaded with gold, the effect of potassium is nulled by silver, and the activity of AuAg + 0.15 at%K/CZ and AuAg + 0.30 at%K/CZ is the same as that of the monometallic Au catalyst. Conversely, when the reaction is carried out in a complex stream, containing CO, C3H8, NO, O2, and water vapor, the presence of water vapor leads to higher CO conversion as well as increased NO2 formation and slightly suppresses the C3H8 combustion.

Plasmonic Photocatalysts

Plasmonic photocatalysts, i [...]

Au-Ag alloy nanoparticle-incorporated AgBr plasmonic photocatalyst

A solid-phase photochemical method produces Au-Ag alloy nanoparticles (NPs) with a sharp size distribution and varying composition in AgBr crystals (Au-Ag@AgBr). These features render Au-Ag@AgBr promising as a material for the plasmonic photocatalyst further to provide a possibility of elucidating the action mechanism due to the optical tunability. This study shows that the visible-light activity of Au-Ag@AgBr for degradation of model water pollutant is very sensitive to the alloy composition with a maximum at the mole percent of Au to all Ag in AgBr (y) = 0.012 mol%. Clear positive correlation is observed between the photocatalytic activity and the quality factor defined as the ratio of the peak energy to the full width at half maximum of the localized surface plasmon resonance band. This finding indicates that Au-Ag@AgBr works as a local electromagnetic field enhancement-type plasmonic photocatalyst in which the Au-Ag NPs mainly promotes the charge separation. This conclusion was further supported by the kinetic analysis of the light intensity-dependence of external quantum yield.