Modification of BiOI Microplates with CdS QDs for Enhancing Stability, Optical Property, Electronic Behavior toward Rhodamine B Decolorization, and Photocatalytic Hydrogen Evolution

Abstract

Fast recombination of photoinduced charge carriers is a major problem in the case of semiconductor based photocatalysts, which must be solved for their potential application in photocatalysis. In this work, photostable CdS QDs/BiOI composites have been successfully fabricated by a two-step precipitation–deposition method. The prepared samples were characterized by X-ray diffraction (XRD), UV–vis diffuse reflection spectroscopy (UV–vis DRS), photoluminescence (PL) spectroscopy, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Mott–Schottky, and electrochemical impedance analysis. The potential applications of CdS QDs/BiOI composite materials have been tested toward decolorization of rhodamine B (RhB) solution and hydrogen generation under solar light and visible light irradiation, respectively. It has been observed that hydroxyl radicals, electrons, and holes played a major role in decolorization of RhB solution. Among all prepared photocatalysts, 4% CdS QDs/BiOI composite was able to decolorize 82% of RhB solution in 1 h and 203 μmol/h of H2 under solar light and visible light irradiation, respectively. The highest activity has been ascribed to optimal loading of CdS QDs, good formation of composites, and the lowest recombination of charge carriers.

Strongly Coupled g‐C3N4 Nanosheets‐Co3O4 Quantum Dots as 2D/0D Heterostructure Composite for Peroxymonosulfate Activation

“…Moreover, the distances of ≈0.200 and ≈0.243 nm correspond to the (400) and (311) planes in the spinel Co 3 O 4 lattice, respectively (Figure H) . Obviously, high crystallinity and ultrasmall particle size will accelerate photogenerated carrier to diffuse toward the surface, thus enhances its photocatalytic activity . Furthermore, both Co 3 O 4 QDs and CNNS are in tight contact with each other to form heterojunction in the interfacial area, which can efficiently retard the photogenerated electron/hole recombination and enhance the possibility of photogenerated charge participating in AOPs.…”

“…With the increment of CNNS amount in the Co 3 O 4 /CNNS composites, the peak intensities of the CNNS increase with decreasing Co 3 O 4 intensities. Moreover, the crystallite size of Co 3 O 4 QDs is calculated to be 2.6 nm, according to the Scherrer equation and the prominent (311) diffraction peak, which is smaller than its excitonic Bohr radius (≈5–6 nm) …”

“…The HRTEM images further confirmed the anchoring of Co 3 O 4 QDs on CNNS nanosheets and demonstrated the formation of Co 3 O 4 /CNNS heterojunction, in which the particle size of Co 3 O 4 QDs was centered at ≈2.2–3.2 nm, matching well with the statistical particle size distribution diagram (Figure F–H). That is, the particle size of Co 3 O 4 QDs is small enough to exhibit the quantum confinement effect . Moreover, the distances of ≈0.200 and ≈0.243 nm correspond to the (400) and (311) planes in the spinel Co 3 O 4 lattice, respectively (Figure H) .…”

Steering Charge Kinetics of Tin Niobate Photocatalysts: Key Roles of Phase Structure and Electronic Structure

“…The positive slope was observed in the Schottky plots of all the products shown in Additional file 1: Figure S7 which demonstrated that the photocatalysts were assigned to n-type semiconductors [77, 78]. The flat band potentials ( E fb ) of the samples can be estimated using the extrapolation of the Mott-Schottky plot at the frequency of 1000 Hz and found to be − 0.685 eV for the SnNb 2 O 6 , − 0.67 eV for the mixed phases of SnNb 2 O 6 and Sn 2 Nb 2 O 7 , and − 0.626 eV for the Sn 2 Nb 2 O 7 .…”

LaCoO3 acts as a high‐efficiency co‐catalyst for enhancing visible‐light‐driven tetracycline degradation of BiOI

“…Among them, bismuth oxyiodide (BiOI), as a p ‐type semiconductor with narrow band gap energy ( ca . 1.8 eV), has rapidly sparked numerous interest as a protuberant and efficient visible‐light‐driven photocatalyst for solar energy conversion and environmental management owing to its excellent merits of supreme optical and electrical properties, unique layered structure, high dipole moment, high chemical stability, nontoxicity and low cost . More importantly, BiOI has highly anisotropic layered tetragonal matlockite structure with [Bi 2 O 2 ] 2+ slabs interleaved by double slabs of iodine atoms, which are beneficial to impart an internal static electric field between the [Bi 2 O 2 ] 2+ and I ‐ slab along the [001] direction, which is advantageous to the separation of photo‐induced electron hole pairs .…”