Perovskite-like photocatalyst, PbBiO2Br/PbO/g-C3N4: Synthesis, characterization, and visible-light-driven photocatalytic activity

Enhanced piezocatalytic and piezo-photocatalytic dye degradation via S-scheme mechanism with photodeposited nickel oxide nanoparticles on PbBiO2Br nanosheets

The fabrication of an S-scheme heterojunction demonstrates as an efficient strategy for achieving efficient charge separation and enhancing catalytic activity of piezocatalysts. In this study, a new S-scheme heterojunction was fabricated on the PbBiO2Br surface through the photo-deposition of NiO nanoparticles. It was then employed in the piezoelectric catalytic degradation of Rhodamine B (RhB). The results demonstrate that the NiO/PbBiO2Br composite exhibits efficient performance in piezocatalytic RhB degradation. The optimal sample is the NiO/PbBiO2Br synthesized after 2 h of irradiation, achieving a RhB degradation rate of 3.11 h-1, which is 12.4 times higher than that of pure PbBiO2Br. Simultaneous exposure to visible light and ultrasound further increases in the RhB degradation rate, reaching 4.60 h-1, highlighting the synergistic effect of light and piezoelectricity in the NiO/PbBiO2Br composite. A comprehensive exploration of the charge migration mechanism at the NiO/PbBiO2Br heterojunction was undertaken through electrochemical analyses, theoretical calculations, and in-situ X-ray photoelectron spectroscopy analysis. The outcomes reveal that p-type semiconductor NiO and n-type semiconductor PbBiO2Br possess matching band structures, establishing an S-scheme heterojunction structure at their interface. Under the combined effects of band bending, interface electric fields, and Coulomb attraction, electrons and holes migrate and accumulate on the conduction band of PbBiO2Br and valence band of NiO, respectively, thereby achieving effective spatial separation of charge carriers. The catalyst's synergistic photo-piezoelectric catalysis effect can be ascribed to its role in promoting the generation and separation of charge carriers under both light irradiation and the piezoelectric field. The results of this investigation offer valuable insights into the development and production of catalytic materials that exhibit outstanding performance through the synergy of piezocatalysis and photocatalysis.

Experimental and computational study of metal oxide nanoparticles for the photocatalytic degradation of organic pollutants: a review

Photocatalysis is a more proficient technique that involves the breakdown or decomposition of different organic contaminants, various dyes, and harmful viruses and fungi using UV or visible light solar spectrum. Metal oxides are considered promising candidate photocatalysts owing to their low cost, efficiency, simple fabricating method, sufficient availability, and environment-friendliness for photocatalytic applications. Among metal oxides, TiO2 is the most studied photocatalyst and is highly applied in wastewater treatment and hydrogen production. However, TiO2 is relatively active only under ultraviolet light due to its wide bandgap, which limits its applicability because the production of ultraviolet is expensive. At present, the discovery of a photocatalyst of suitable bandgap with visible light or modification of the existing photocatalyst is becoming very attractive for photocatalysis technology. However, the major drawbacks of photocatalysts are the high recombination rate of photogenerated electron-hole pairs, the ultraviolet light activity limitations, and low surface coverage. In this review, the most commonly used synthesis method for metal oxide nanoparticles, photocatalytic applications of metal oxides, and applications and toxicity of different dyes are comprehensively highlighted. In addition, the challenges in the photocatalytic applications of metal oxides, strategies to suppress these challenges, and metal oxide studied by density functional theory for photocatalytic applications are described in detail.

Photocatalytic CO2 Reduction to CH4 and Dye Degradation Using Bismuth Oxychloride/Bismuth Oxyiodide/Graphitic Carbon Nitride (BiOmCln/BiOpIq/g-C3N4) Nanocomposite with Enhanced Visible-Light Photocatalytic Activity

The use of visible-light-driven photocatalysts in wastewater treatment, photoreduction of CO2, green solar fuels, and solar cells has elicited substantial research attention. Bismuth oxyhalide and its derivatives are a group of visible-light photocatalysts that can diminish electron–hole recombination in layered structures and boost photocatalytic activity. The energy bandgap of these photocatalysts lies in the range of visible light. A simple hydrothermal method was applied to fabricate a series of bismuth oxychloride/bismuth oxyiodide/grafted graphitic carbon nitride (BiOmCln/BiOpIq/g-C3N4) sheets with different contents of g-C3N4. The fabricated sheets were characterized through XRD, TEM, SEM-EDS, XPS, UV-vis DRS, PL, and BET. The conversion efficiency of CO2 reduction to CH4 of BiOmCln/BiOpIq of 4.09 μmol g−1 can be increased to 39.43 μmol g−1 by compositing with g-C3N4. It had an approximately 9.64 times improvement. The photodegradation rate constant for crystal violet (CV) dye of BiOmCln/BiOpIq of k = 0.0684 can be increased to 0.2456 by compositing with g-C3N4. It had an approximately 3.6 times improvement. The electron paramagnetic resonance results and the quenching effects indicated that 1O2, •OH, h+, and •O2− were active species in the aforementioned photocatalytic degradation. Because of their heterojunction, the prepared ternary nanocomposites possessed the characteristics of a heterojunction of type II band alignment.

Effect of nonmetals (B, O, P, and S) doped with porous g-C3N4 for improved electron transfer towards photocatalytic CO2 reduction with water into CH4

Photocatalytic conversion of carbon dioxide (CO₂) into gaseous hydrocarbon fuels is an auspicious way to produce renewable fuels in addition to greenhouse gas emission mitigation. In this work, non-metals (B, O, P, and S) doped graphitic carbon nitride (g-C₃N₄) was prepared via solid-state polycondensation of urea for photocatalytic CO₂ reduction into highly needed methane (CH₄) with water under UV light irradiation. The various physicochemical characterization results reveal the successful incorporation of B, O, P, and S elements in the g-C₃N₄ matrix. The maximum CH₄ yield of 55.10 nmol/(mL_H2O.g_cat) over S-doped g-C₃N₄ has been obtained for CO₂ reduction after 7 h of irradiation. This amount of CH₄ production was 1.9, 1.4, 1.7, and 2.4-folds higher than B, O, P and bare g-C₃N₄ samples. The doping of S did not enlarge the surface area and photon absorption ability of the g-C₃N₄ sample, but this significant improvement was evidently due to effective charge separation and migration. The observed results imply that the doping of non-metal elements provides improved charge separation and is an effective way to boost photocatalyst performance. This work offers an auspicious approach to design non-metal doped g-C₃N₄ photocatalysts for renewable fuel production and would be promising for other energy application.

Facile sonochemical method for preparation of Cs2HgI4 nanostructures as a promising visible-light photocatalyst

Attempts are continuing to discover novel and efficient solutions to promote water grade and industrial sewage treatment. For the first time, we present a novel Cs₂HgI₄ photocatalyst functional below visible radiation. Cs₂HgI₄ nano photocatalyst has been prepared via an accelerated sonochemical approach to examine its photocatalytic progression. Several construction circumstances, including variations of power and time of sonication and performance of different surfactant types, were conducted to produce fine particles with uniform morphology. FESEM images attested that the presence of surfactant had an adverse and destructive effect on the morphology of products. The bandgap for Cs₂HgI₄ nanostructures was determined to be approximately 2.3 eV, making these nanostructures desirable for photocatalytic applications. The photocatalytic data confirmed that Cs₂HgI₄ could destroy acidic coloring agents greater than basic ones. The highest photodegradation was observed for methyl orange with 76.8%.

Controlled hydrothermal synthesis of BiOxCly/BiOmBrn/g-C3N4 composites exhibiting visible-light photocatalytic activity

The first systematic synthesis of bismuth oxychloride/bismuth oxybromide/graphitic carbon nitride (BiO_xCl_y/BiO_mBr_n/g-C₃N₄) nano-composites used a controlled hydrothermal method. The structure, morphology and characteristic of BiO_xCl_y/BiO_mBr_n/g-C₃N₄ photocatalyst were measured by XRD, UV-vis-DRS, FT-IR, FE-TEM, FE-SEM-EDS, PL, BET, HR-XPS and EPR. Under visible light irradiation, the photodegradation activity was evaluated for the decolorization of crystal violet (CV) and 2-hydroxybenzoic acid (2-HBA) in aqueous solution. The catalytic performance showed that, when using sample BB2C1-4-250-30 wt% g-C₃N₄ composite as a photocatalyst, the best reaction-rate-constant (k) was 0.071 h^-1. It was 1.5 times higher than the k value of BB2C1-4-250 as a photocatalyst. From the scavenging effect of various scavengers, the results of EPR showed that reactive OH was the main scavenger, while O₂^-, h⁺ and ¹O₂ were the second scavenger in CV degradation. In this study, a possible photodegradation mechanism was proposed and discussed. In this work, our method of BiO_xCl_y/BiO_mBr_n/g-C₃N₄ preparation could be used for future mass production and the BiO_xCl_y/BiO_mBr_n/g-C₃N₄ composite materials could be applied to the environmental pollution control in future.

Bifunctional Z-Scheme Ag/AgVO3/g-C3N4 photocatalysts for expired ciprofloxacin degradation and hydrogen production from natural rainwater without using scavengers

To maximize the employment of sustainable solar energy in treating the recalcitrant pollutant and hydrogen energy production, the development of a highly efficient photocatalyst is desirable. Herein, a Z-scheme Ag/AgVO₃/g-C₃N₄ photocatalyst was synthesized via a wet-impregnation method. The amount of Ag/AgVO₃ deposited onto g-C₃N₄ has a significant effect on the photocharge carrier separation and migration of the as-developed Z-scheme photocatalyst. It was found that 0.5 wt % Ag/AgVO₃/g-C₃N₄ photocatalyst exhibited a profound photocatalytic degradation performance with 82.6% ciprofloxacin removal and 3.57 mmol/h of hydrogen produced from natural rainwater under visible-light irradiation. Additionally, the apparent quantum efficiency (AQE) of this sample was 9.95% at 420 nm which is four times higher than the pure sample. The remarkable photocatalytic performance was attributed to the enhanced crystallographic structure, evidently from the XRD and XPS analysis. Moreover, the intimate contact between Ag/AgVO₃ and g-C₃N₄ nanoparticles allows the smooth photocharge carrier separation and migrations, resulting in superior photocatalytic performance in comparison to the pure samples. Interestingly, the profound photocatalytic activity demonstrated here was achieved without the addition of any sacrificial reagents. This work demonstrates the feasibility of utilizing visible-light-driven photocatalysts in treating the recalcitrant antibiotic pollutants and producing hydrogen from natural rainwater.

Enhanced photocatalytic removal of amoxicillin with Ag/TiO2/mesoporous g-C3N4 under visible light: property and mechanistic studies

In present study, an efficient ternary Ag/TiO₂/mesoporous g-C₃N₄ (M-g-C₃N₄) photocatalyst was successfully synthesized through depositing Ag nanoparticles (NPs) on the surface of TiO₂/M-g-C₃N₄ heterojunction. Ag/TiO₂/M-g-C₃N₄ nanocomposite displayed the highest degradation efficiency for amoxicillin (AMX) compared to TiO₂/M-g-C₃N₄ heterojunction, M-g-C₃N₄, and bulk-g-C₃N₄ (B-g-C₃N₄). The removal efficiency of AMX in real situation, surface water (SW), hospital wastewater (HW), and waste water treatment plant (WWTP) also were studied to illustrate the effectiveness of Ag/TiO₂/M-g-C₃N₄ photocatalysts. The vulnerable atoms in AMX structure were revealed through DFT calculation. Additionally, the dominating active groups produced in time of the photocatalytic procedure were determined on account of free radical trapping experiments and ESR spectra. The mechanism of photocatalytic degradation was proposed and verified. The transfer of the electrons and the inhibition of the recombination of photogenerated electron-holes were enhanced effectively under the synergistic effect of the Ag NPs and TiO₂. As a consequence, the catalytic activity of the composite was improved under visible light.

Preparation of Ag-AgVO3/g-C3N4 composite photo-catalyst and degradation characteristics of antibiotics

The degradation of tetracycline by silver vanadate (AgVO₃), graphite-like carbon nitride (g-C₃N₄) and their composites was studied by visible light photocatalysis. Their structures and morphologies were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Their degradation intermediates were analyzed by GC-MS. Nanorod silver vanadate was synthesized by hydrothermal method. The results show that the gap between nanorods is reduced by adding spinning carbon nitride, and the photocatalytic performance of the composite is stronger than that of single material. The reaction rate constants of Ag-AgVO₃/g-C₃N₄ composites were 0.0298 min^-1, 2.4 and 2.0 times that of g-C₃N₄ (K=0.0125 min-1) and AgVO₃ (K=0.0152 min-1), respectively. At 120 minutes, the degradation rate of the composites reached 83.6%. The degradation of tetracycline was confirmed by GC-MS, and a possible degradation process was proposed.