Role of thermal decomposition process in the photocatalytic or photoluminescence properties of BiPO₄ polymorphs

Abstract

Thermal decomposition process was used to obtain modified photocatalytic and/or photoluminescence properties of bismuth phosphate polymorphs. The precursor BiPO4, 0.7H2O was synthesized by a coprecipitation route. The observed polymorphs were the hexagonal P3121 hydrate phase BiPO4, 0.7H2O at 25°C, a mix system of hexagonal and monoclinic P21/n phases at 200°C and 400°C, a mix system of monoclinic phases P21/n and P21/m at 600°C, and a unique monoclinic phase P21/m at 900°C. The X‐ray diffraction analyses allowed evidencing lattice deformations due to structural defects. The photocatalytic activities in the presence of rhodamine B in aqueous solution were determined using UV light irradiation. The best photocatalytic efficiencies were observed with the mix systems resulting from thermal decomposition at 400 and 600°C. Photoluminescence experiments performed under UV‐laser light irradiation revealed unexpected emissions in the green‐orange range, with optimal intensities for the mix systems observed at 400°C. The role of structural defects resulting from decomposition process is discussed. Practitioner points Thermal decomposition is used to introduce structural defects in BiPO4 polymorphs The BiPO4 intermediate systems are used to photodegrade rhodamine B Active species trapping experiments are performed Photoluminescence experiments highlight green‐orange emissions Structural defects are at the origin of this photoluminescence

Electrodeposited ZnO Nanorods as Efficient Photoanodes for the Degradation of Rhodamine B

“…The first‐order kinetic model is commonly expressed as the following equation. [ 43 ] where K is the degradation rate constant (min −1 ) and C 0 and C t are the concentrations (mg L −1 ), of RhB when reaction time was 0 and t , respectively. The linear fit between ln( C 0 / C t ) and reaction time t of the two different ZnO films follows a pseudo‐first‐order kinetics behavior.…”

Phase Transformation, Photocatalytic and Photoluminescent Properties of BiPO4 Catalysts Prepared by Solid-State Reaction: Degradation of Rhodamine B

“…There are several methods for synthesizing phosphate-based materials in powder form. In our previous study concerning BiPO 4 [30,42,53], all samples were obtained from coprecipitation technique followed by thermal treatment at various temperatures [61]. In this work, we developed a new route based on solid-state reaction.…”

“…The broad emission bands observed in the range 400 to 800 nm in all the powders of the BiP-Θ samples with Θ = 500, 550, 600, 650 and 700 • C (Figure 8a), show similar profiles with a maximum at 515 ± 20 nm. The results in the literature have shown that, in the case of Bi 3+ isolated in a solid matrix, the allowed transition of Bi 3+ is 3 P 1 → 1 S 0 , and that it is characterized by emission spectra with wavelengths close to 470 nm (2.6 eV) [61]. In the case of the study of the three polymorphic varieties of BiPO 4 , the Bi 3+ emissions under excitation at 360 nm were observed at 450 nm (2.8 eV) for the hexagonal and monoclinic M 1 phases.…”

“…In our recent work [61], BiPO 4 samples were synthesized from polycrystalline precursors obtained by coprecipitation method, then, thermally treated at temperatures Θ of 200, 400, 600 and 900 • C during 3 h. The progressive formation of three polymorphs, hexagonal phase at 200 • C, monoclinic P2 1 /n at intermediate temperatures and P2 1 /m at 900 • C, allowed observing different behaviors of photocatalytic activities and photoluminescence emissions. The role of thermal decomposition was to modify crystal structures, crystallite dimensions and morphologies to obtain or vary certain properties.…”

Barium Hydrogen Phosphate Electrodes for High Electrocatalytic and Photoelectrocatalytic Degradation of Rhodamine B in Neutral Medium: Optimization by Response Surface Methodology

“…After the electrodeposition, BaHPO 4 thin films were rinsed with distilled water several times before electrodegradation experiments in which RhB was used as a model dye (Fig. 1) [44].…”