Influence of the crystal structure of Ag2CO3 on the photocatalytic activity under visible light of Ag2CO3-Palygorskite nanocomposite material

Abstract

A B S T R A C TIn a companion paper, it has been demonstrated the remarkably beneficial effect of palygorskite clay (Pal) fibers as support material coupled to appropriate thermal treatments and aging under CO 2 atmosphere in monitoring the phase composition of Ag 2 CO 3 -Pal composite. In this new nanocomposite material, the structure of the functional component Ag 2 CO 3 can be controlled from 100% stable monoclinic (m) to 100% metastable hexagonal β through an adjusted mixture of m-and β-Ag 2 CO 3 . The present study deals with the assessment of the visible photocatalytic properties of these various nanocomposite materials towards the removal of Orange G dye from aqueous solutions. It was found that the Ag 2 CO 3 -Pal nanocomposite in which Ag 2 CO 3 was single-phased and crystallized with the stable monoclinic structure was more active than the one crystallizing entirely with the metastable β-Ag 2 CO 3 structure. Nevertheless, the composite material containing a mixture of both Ag 2 CO 3 phases with a relative content of 32% of β-and 68% of m-phase was found to be the most photoactive compound of the series. This behavior reveals likely a synergetic effect between both phases in the photocatalytic degradation of the dye under visible light.

On the key role of the surface of palygorskite nanofibers in the stabilization of hexagonal metastable β-Ag2CO3 phase in palygorskite-based nanocomposites

“…Specific thermal treatments under CO 2 coupled to aging for several hours to months were studied on the phase composition CO of pure Ag 2 CO 3 and (ii) of Ag 2 CO 3 supported palygorskite composites. This investigation help for establishing correlations between the phase composition of Ag 2 CO 3 in Ag 2 CO 3 /palygorskite new composites and their photocatalytic activity in the visible range which was reported in a companion paper (Lakbita et al, 2019). The importance of this study is reinforced by the photocatalytic properties since we found that the Ag 2 CO 3 -Pal nanocomposite in which Ag 2 CO 3 was single-phased and crystallized with the stable monoclinic structure was more active than the one crystallizing entirely with the metastable j3-Ag 2 CO 3 structure.…”

“…Subsequently the photocatalytic activity of these three categories of Ag 2 CO 3 /Pal nanocomposites with various phase compositions has been studied under visible light irradiation. Details reported in a companion paper (Lakbita et al, 2019) that the nanocomposite in which Ag 2 CO 3 was single-phased with the hexagonal structure was Jess active than the one crystallizing entirely with the stable monoclinic structure. How ever, the nanocomposite material containing a mixture of both Ag 2 CO 3 phases with a relative content of 32% of 13-and 68% of m-phase was found to be the most photoactive material of the series.…”

“…The motivation of this paper is to improve the fondamental un derstanding of the stabilization of the j3-Ag 2 CO 3 phase induced by the palygorskite surface, which leads to an original route to synthesize new Ag 2 CO 3 /Pal photocatalysts exhibiting a high activity under the visible light, as recently demonstrated (Lakbita et al, 2019). In addition, the phase composition of these nanocomposites can be controlled and the activity of the metastable j3-phase was studied while its synthesis is difficult by other methods.…”

Preparation and Photocatalytic Performance of Dumbbell Ag2CO3–ZnO Heterojunctions

“…Silver-based materials such as AgCl, Ag 3 PO 4 , Ag 2 WO 4 , and Ag 2 CO 3 − are promising photocatalysts, which can absorb visible light. Ag 2 CO 3 is a new type of high-efficiency visible light catalyst with a narrow band gap, which shows good activity in photocatalytic degradation of colored dyes . The separation efficiency of photogenerated electrons and holes can be improved by constructing a heterojunction. , The introduction of Ag 2 CO 3 into ZnO can notably improve the photocatalytic performance of ZnO because the charge separation will be greatly enhanced by the heterojunction between ZnO and Ag 2 CO 3 . , Therefore, a heterojunction combining ZnO with Ag 2 CO 3 can broaden the optical response range of ZnO, promote the separation of photogenerated electrons and holes, and markedly enhance the photocatalytic activity of ZnO.…”

“…Ag 2 CO 3 is a new type of high-efficiency visible light catalyst with a narrow band gap, which shows good activity in photocatalytic degradation of colored dyes. 31 The separation efficiency of photogenerated electrons and holes can be improved by constructing a heterojunction. 32,33 The introduction of Ag 2 CO 3 into ZnO can notably improve the photocatalytic performance of ZnO because the charge separation will be greatly enhanced by the heterojunction between ZnO and Ag 2 CO 3 .…”