Silver-modified octahedral anatase particles as plasmonic photocatalyst

Abstract

Graphical abstract

Morphology-Governed Performance of Plasmonic Photocatalysts

“…Interestingly, it is found that an increase in the size of Au NPs results in an increase in the photocatalytic activity under vis irradiation, probably because of larger areas with field enhancement, as shown in Figure 5. Similar findings have been obtained for Ag-modified OAP samples, i.e., an increase in the activity with an increase in the size of Ag NPs [44]. Moreover, the participation of the mobile electrons in the mechanism of 2-propanol oxidation under vis irradiation has been confirmed by time-resolved microwave conductivity (TRMC).…”

“…Interestingly, the comparison between faceted and commercial titania samples shows that Au/OAP exhibits ca. one order in magnitude higher activity than that by Au-modified commercial titania samples (of similar properties; Figure 7a), suggesting fast charge carriers' separation (Figure Similar findings have been obtained for Ag-modified OAP samples, i.e., an increase in the activity with an increase in the size of Ag NPs [44]. Moreover, the participation of the mobile electrons in the mechanism of 2-propanol oxidation under vis irradiation has been confirmed by time-resolved microwave conductivity (TRMC).…”

“…At the same time, to keep noble metal at zero-valent state, oxidation of some compounds on the surface of electron-deficient noble metal must proceed [38]. Although, there are no direct proof for electron transfer (as detected electrons might also origin from energy transfer in some cases), there are many studies suggesting this mechanism as the most probable via various experimental approaches, including femtosecond transient absorption spectroscopy (electrons transferred from Au to TiO 2 ) [39,40], EPR spectroscopy (different oxidation species under UV and vis irradiation) [41,42], time-resolved microwave conductivity (TRMC) method (conductivity under vis irradiation only for titania modified with noble metals: Au [43] and Ag [44]), electrochemical study (shift of electrode potential to negative or positive values and generation of anodic or cathodic photocurrent depending on electrode configuration, i.e., ITO/TiO 2 /Au or ITO/Au/TiO 2 , respectively, as shown in Figure 3) [45]. In the case of electron transfer, noble metals work as sensitizers (being even named as "plasmonic sensitizers"), and thus "hot" electron transfer from noble metal to CB of semiconductor has been proposed as the first step of plasmonic photocatalysis [30].…”

Photocatalytic and Antimicrobial Properties of Ag2O/TiO2 Heterojunction

“…Figure 6 presents the possible mechanism of methanol dehydrogenation. Considering the darkening of suspension during irradiation (right parts of Figure 5 vs. Figure 7) in highly reductive conditions (anaerobic, methanol, UV), it is proposed that Ag 2 O was reduced forming zero-valent silver deposits (+1.17 V vs. SHE) being the co-catalyst for hydrogen evolution [22][23][24]57]. reductive properties of Ag2O/TiO2 than that of bare TiO2 (more negative CB of Ag2O than that of TiO2).…”

“…The modification of titania with silver nanoparticles (NPs) or mixed silver forms (Ag(0), Ag + , Ag 2+ ) to prepare photocatalysts has already been performed by many research groups [21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37]. However, in the case of Ag 2 O/TiO 2 system, there are only a few research papers and the mechanism of the coupling is still not fully understood [38][39][40][41][42][43][44][45][46][47][48][49].…”