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With the exceptional advantages of safety, greenness, and low cost, photocatalytic H2O2 generation has kindled a wonderful spark, although being severely hampered by the terrible photoinduced exciton recombination, migration, and surface decomposition. Here, employing reflux method, the Cd–Mo–Se quantum dots of varying molar ratios of Cd and Mo were synthesized using thioglycolic acid as the capping ligand to regulate their growth. This type of metal alloying promotes rapid charge migration, improves light harvesting, and reduces the rate of charge recombination. The improved optoelectronic properties and boosted activity of Cd-rich ternary CMSe-1 QDs led to the observed exceptional photocatalytic H2O2 yield of 1403.5 μmol g−1 h−1 (solar to chemical conversion efficiency, 0.27%) under visible light, outperforming the other ternary and Se-based QD photocatalysts. Additionally, CMSe-1 shows 93.6% (2 h) hazardous Cr(VI) photoreduction. The enhanced catalytic performance of CMSe-1 corresponds to effective charge carrier separation and transfer efficiency, well supported by PL, TRPL, and electrochemical measurements. Photocatalytic H2O2 production was also studied under varying experimental conditions and the scavenger test suggests a superoxide radical intermediate 2-step single electron reduction pathway. The catalyst-assisted Cr(VI) reduction is substantiated by the zero-order kinetics as well as the determination of the pHPZC value. The catalyst can be employed for a maximum of four times while retaining its activity, according to the photostability and reusability test outcomes. This research presents interesting approaches for producing ternary QDs and modified systems for efficient photocatalytic H2O2 production and Cr(VI) reduction. [ABSTRACT FROM AUTHOR]

Designing a heterojunction through oxygen vacancy (OV) has been considered as a well-accepted stratagem for enhanced photo-Fenton activity. Therefore, we have adopted a combination of hydrothermal and calcination methods to fabricate an abundant step-scheme photocatalyst by uniting ZnFe2O4 with an oxygen-defect-oriented WO3 semiconductor and verified their activities towards levofloxacin (LVX) degradation under solar-light illumination. The as-synthesized 15%WO3−X/ZnFe2O4 binary hybrid displayed increased photo-Fenton activity for LVX degradation (kapp value 4–7 times greater than that of pure semiconductors). The increased activity can be attributed to effective charge transmission occurring between the conduction band of defective WO3−X and the valence band of ZnFe2O4 bridged through mediator-free OVs. The existence of OVs was well-supported with the assistance of Raman, XPS, and EPR characterization, whereas the proposed S-scheme charge transfer mechanism was proved by hydroxyl and super-oxide radical generation experiments. Furthermore, the photo-Fenton system constructed by H2O2 and continuous Fe(III)/Fe(II) conversion resulted in high concentration of ˙OH radical that ultimately encouraged faster LVX degradation. Through the identification of reaction intermediates via LC-MS analysis, the LVX degradation pathways were speculated. [ABSTRACT FROM AUTHOR]

Achieving organic transformation reactions using green synthesis methods under mild conditions is always an aspiration of scientists. In the present findings, a Zn–Cr layered double hydroxide (LDH)/graphene oxide (GO) nanocomposite modified with Au–Ag noble metal nanoparticles (NPs) was synthesized via the in situ crystallization of a LDH over a GO surface followed by the simultaneous photo-deposition of a metal alloy and the reduction of GO to reduced graphene oxide (RGO) under UV light irradiation, resulting in AuAg@GO/LDH. All prepared samples were suitably analysed via various sophisticated techniques to explore their structural, morphological, optical and compositional behaviours. The characterization outcomes showed the uniform distribution of AuAg alloyed NPs with a typical diameter of around ∼3 nm on the facade of the GO/LDH nanocomposite. The conversion of GO to RGO is confirmed via Raman analysis. This bimetallic alloy-based nanocomposite provides a novel platform for artificial photocatalysis, and shows excellent catalytic activity for the performed tandem redox reactions. The combined effects of the plasmon active AuAg alloy, the visible photon-responsive ZnCr LDH and the electron trapping and transporting properties of GO illustrate the existence of an intensified green photochemical process, which can be extensively developed to be applied to tandem liquid phase photocatalytic organic reactions. Here the photogenerated electrons and holes can be directly utilized by nitrobenzene (NB) and benzyl alcohol (BA) to produce aniline (AL) and benzaldehyde (BAD) via GO, respectively. This selective photoredox reaction is a synergistic type of process that proceeds via producing and consuming protons. The effective separation of charge carriers is well supported by photoluminescence (PL) studies. Compared to the parent GO/LDH and Au and Ag singly-modified GO/LDH samples, AuAg@GO/LDH revealed proficient photocatalytic potential owing to the existence of combined surface plasmon resonance (SPR) effects, characterised through UV-visible diffuse reflectance spectroscopy (UV-vis DRS), generating hot electrons from both photoexcited Au and Ag atoms under visible light illumination. The AuAg@GO/LDH hybrid photocatalyst showed ∼2.5 times better performance than GO/LDH, without any indication of leached metal or metal alloy over five runs. [ABSTRACT FROM AUTHOR]

In the present study, a series of Ce2Zr2O7@rGO nanocomposites were synthesized using a simple solution combustion method followed by a photoreduction technique. The as-prepared samples were well characterised using various analytical techniques to determine the morphological, optical, structural, electrochemical and compositional properties. The presence of oxygen defects was observed from Raman and photoluminescence spectra. The photoreduction of GO to rGO was determined from Raman and Fourier-transform infrared (FTIR) spectroscopy results. The role of rGO proved to be quite significant for the enhanced photocatalytic activity of the nanocomposites. The synergistic communication between Ce2Zr2O7 and rGO accelerates the photoreduction of 4-nitrophenol along with the degradation of ciprofloxacin under visible light irradiation. Of the rGO nanocomposites, 3 wt% GO loaded Ce2Zr2O7 reduces 99% of 20 ppm of 4-nitrophenol to 4-aminophenol in 120 min and decomposes 10 ppm of ciprofloxacin by up to 89% in 60 min. The significant enhancement in the activity of the Ce2Zr2O7@rGO nanocomposite was ascribed to the effective charge separation of excitons through π-conjugation of graphene at the interface, which is well supported by the impedance, photoluminescence and photocatalytic results. [ABSTRACT FROM AUTHOR]