Efficient visible-light photocatalytic activity by band alignment in mesoporous ternary polyoxometalate–Ag₂S–CdS semiconductors

Abstract

Porous multicomponent semiconductor materials show improved photocatalytic performance due to the large and accessible pore surface area and high charge separation efficiency. Here we report the synthesis of well-ordered porous polyoxometalate (POM)-Ag2S-CdS hybrid mesostructures featuring a controllable composition and high photocatalytic activity via a two-step hard-templating and topotactic ion-exchange chemical process. Ag2S compounds and polyoxometalate cluster anions with different reduction potentials, such as PW12O40(3-), SiW12O40(4-) and PMo12O40(3-), were employed as electron acceptors in these ternary heterojunction photocatalysts. Characterization by small-angle X-ray scattering, X-ray diffraction, transmission electron microscopy and N2 physisorption measurements showed hexagonal arrays of POM-Ag2S-CdS hybrid nanorods with large internal BET surface areas and uniform mesopores. The Keggin structure of the incorporated POM clusters was also verified by elemental X-ray spectroscopy microanalysis, infrared and diffuse-reflectance ultraviolet-visible spectroscopy. These new porous materials were implemented as visible-light-driven photocatalysts, displaying exceptional high activity in aerobic oxidation of various para-substituted benzyl alcohols to the corresponding carbonyl compounds. Our experiments show that the spatial separation of photogenerated electrons and holes at CdS through the potential gradient along the CdS-Ag2S-POM interfaces is responsible for the increased photocatalytic activity.

Ordered Mesoporous Polyoxometalate–Organosilica Frameworks as Efficient Photocatalysts of the Hydrogen Evolution Reaction

“…In principle, this can weaken the reduction ability of [PW 11 O 39 ] 7− and, to a greater extent, [PMo 11 O 39 ] 7− clusters, to split water into H 2 . Previously, a similar activity trend was observed for the photochemical oxidation of organic compounds on POM catalysts with different redox potentials . We performed the same experiments with SiW 11 /MES polymers featuring loadings of SiW 11 of 9 and 25 wt %.…”

Role of RGO support and irradiation source on the photocatalytic activity of CdS–ZnO semiconductor nanostructures

“…The CB potential of CdS are E CB = −0.66 eV vs NHE, which is more negative than the E CB of ZnO [62–63]. This relative position of CB of CdS with respect to ZnO leads to the charge transfer from CB of CdS to the CB of ZnO [22].…”

Reviving near infra‐red emission of Ag2S nanoparticles using interfacial defects in the Ag2S@CdS core–shell structure

“…[17,[19][20][21][22][23][24][25][26][27] The morphology of the prepared Ag 2 S/CdS changed dramatically between reports and depended on the type of surfactant, the solvent type, the method of preparation and nucleation of silver sulfide. [17,[19][20][21][22][23][24][25][26][27] For example, match stick-like nanoparticles of Ag 2 S −CdS, in which Ag 2 S catalyzes the formation of CdS nanorods on the side of silver sulfide nanoparticles can be prepared due to control of crystal growth and the type of ligand linkage to CdS, as well as the concentration of silver ions. [21] Similarity of the crystal phases of these reports with the present work shows that control of the synthesis parameters plays an essential role in the formation of the final morphology.…”