Photocatalytic Performance Research Articles

Enriched photocatalytic degradation of methylene orange dye using carbon quantum dots surface-decorated TiO2 nanocomposites

Complex molecules in methylene orange (MO) dye-contaminated water are carcinogenic and mutagenic risks to human health. Carbon quantum dot surface-decorated titanium dioxide nanocomposites (CQD-TiO2 NCs) were synthesized via a sustainable hydrothermal method at concentrations of 1.5–3 mL. These NCs exhibits superior electron transfer, light harvesting capabilities, high stability, easy modification, optical characteristics, and photocatalytic properties. The surface morphology, porosity, physiochemical, and optical features of these CQD-TiO2 NCs were characterized using TEM, UV–Vis, PL, BET, BJH micromeritics, pHzpc, and photoelectrochemical measurements. The prepared NCs were evaluated against the photocatalytic degradation of MO dye molecules using a solar simulator system. The TEM revealed ultra-sensitive and tiny CQD materials with graphite phases ranging from 5 to 10 nm and attached to the octahedron surface of TiO2 NCs. The PL analysis observed three distinct emission peaks in the visible region, attributed to the near band edge, interstitial (Tii), and oxygen vacancy (V0). The BET and BJH analyses were conducted to determine the N2 adsorption-desorption surface area and mesoporous structure with pore sizes ranging from 2 to 50 nm. These NCs showed excellent photocatalytic performance, effectively degrading MO up to 99.00 % in a 3 mL variation, indicating that they could be a great candidate for photocatalytic purification of wastewater containing MO dyes.

Construction of Ag-modified ZnO/g-C3N4 heterostructure for enhanced photocatalysis performance.

ZnO/g-C3N4 heterojunction modified with Ag nanoparticles (ZnO/CN/Ag) was synthesized by depositing ZnO nanorods/Ag nanoparticles onto g-C3N4 nanosheets. Under xenon lamp irradiation, 99% of Rhodamine B (RhB) was degraded by ZnO/CN/Ag-5% composite within 30min, which was much higher than the degradation efficiency of ZnO and ZnO/CN. The synergistic effect of g-C3N4 and ZnO, along with the localized surface plasmon resonance effect of Ag NPs, contributes to the improvement of photocatalytic performance. Ag nanoparticle provides another charge transfer path from g-C3N4 to ZnO, which speeds up the separation of electron-hole pairs. Meanwhile, the catalyst had good stability and recyclability. Finite-difference time-domain method and the density functional theory were used to obtain the charge transfer process. The photodegradation process has been studied in depth.

Development of photoactive ZnS-SiO2 composites on biogenic silica matrix for organic pollutant degradation.

Sulfide ZnS-SiO2 composite photocatalysts with biogenic silica matrix were prepared by sol-gel method based on wet gel and xerogel. FT-IR, SEM, XRD, EDXRF, UV-Vis, and XPS methods were systematically used to characterize the obtained materials. The use of support allowed to obtain stable porous (SBET = 79-105 m2g-1; Vpore = 0.25-0.17 cm3·g-1) ZnS-SiO2 photocatalysts in aqueous solutions. Zn2+ content in methyl orange solution after its degradation was 0.4 MPC. ZnS-SiO2 composites had 3.68-3.70eV band gap. The obtained materials were photoactive under different irradiation conditions (sunlight, UV-light, Xenon light, visible light) due to effective separation of charge carriers (e- and h+). Methyl orange degradation degree under UV light excitation was 35-88%, under sunlight - 11-30%. ZnS-SiO2 composite synthesized using silica xerogel showed a greater photoactivity due to a presence of cone-shaped or cylindrical pores with one open end in its structure and a higher content of ZnS photoactive component. A comparative study of photocatalytic performance of methyl orange degradation by ZnS-SiO2 under UV irradiation was investigated using radical scavengers. •O2- was main active species during MO degradation under UV irradiation, and electrons played additional role during the photocatalytic process.

Ni-Metalized Covalent Organic Cage as a Photocatalyst for Selective Photoreduction of CO2 to CO.

Metal complex-based photocatalysts are promising for CO2 reduction. Their catalytic performances greatly rely on the synergy of ligands and metal ions. Here, we demonstrate an assembly of covalent organic cage (COC) and metal ions for photocatalytic CO2 reduction. The coordinated metal serves as catalytically active site for CO2 reduction, while the cage not only chelates the metal site, but also enhances the local concentration of CO2 around metal site, and decreases the key intermediate reaction energy barrier, thereby promoting the CO2 reduction reaction kinetically and thermodynamically. Accordingly, a Ni metalized COC exhibited outstanding photocatalytic performance in CO2-to-CO conversion under visible light irradiation. This study highlights the feasibility and advantage of organic cages for the construction of photocatalysts for artificial photosynthesis.

Photocatalytic degradation of ampicillin antibiotics in aqueous solution utilizing ZnFe2O4/MWCNTs/TiO2 ternary nanocomposite under solar light irradiation

In this study, a novel photocatalyst composed of zinc ferrite (ZnFe₂O₄), titanium dioxide (TiO₂), and multi-walled carbon nanotubes (MWCNTs) was successfully synthesized via the hydrothermal method, and evaluated for the degradation of ampicillin (AMP) in aqueous solutions. The synthesized nanocomposites were thoroughly characterized using various analytical techniques, including XRD, HR-SEM, HR-TEM, EDX, UV-Vis, FT-IR, BET, and XPS analysis. Crystallite sizes of 24.18 nm for ZnFe₂O₄ and 17.8 nm for TiO₂ were determined. The composite exhibited a band gap of 1.4 eV, indicating its enhanced photocatalytic activity. The photocatalytic performance was assessed under varying conditions, including different nanocomposite dosages (0.3–1 g/L), AMP concentrations (10–50 mg/L), and pH values (2–12). The optimal AMP degradation efficiency of 99.2 % was achieved using 0.7 g/L of the photocatalyst, 10 mg/L of AMP, and a pH of 12 under 90 min of solar irradiation. These optimal parameters were then applied to evaluate AMP degradation using ZnFe2O4, TiO2, and ZnFe2O4/MWCNTs individually, with the degradation rate analyzed using a pseudo-first-order model. The superior photocatalytic efficiency can be primarily attributed to improved charge transfer dynamics and effective electron-hole separation, enabled by the doping of MWCNTs. Hydroxyl radicals (OH•) were identified as the primary reactive species responsible for AMP degradation. Furthermore, the catalyst retained 91 % of its photocatalytic efficiency after eight consecutive cycles, demonstrating excellent stability and reusability. These results underscore the potential of the ZnFe₂O₄/MWCNTs/TiO₂ composite as a highly effective and sustainable photocatalyst for removing pharmaceutical pollutants from aquatic environments.

Saraca asoca-assisted green synthesise of ZnO nanoplatelets for photocatalytic activity and adsorption kinetics

ABSTRACT ZnO nanoplatelets (ZnO NPLs) have been successfully synthesised using microwave-assisted technique (400 W, 180 sec) with the plant extract Saraca-asoca. The surface morphology analysis confirms ZnO’s plate-like nanostructure, leading to the creation of ZnO NPLs. The results show excellent photocatalytic performance (at 125 W for both UV and visible light) and effectiveness against malachite green (MG), methyl orange (MO) and rhodamine B (RhB). Notably, ZnO NPLs break down malachite green (MG) exceptionally well, reaching a maximum degradation efficiency of 92% in under 30 min (UV light). Moreover, ZnO NPLs have been evaluated for MG adsorption characterised by the pseudo-first-order kinetic model, alongside the Freundlich and Langmuir isotherm models. In the Freundlich model, the maximal adsorption capacity is determined to be 331 mg/g. These new faceted ZnO NPLs have a great potential for use in photocatalytic and adsorption processes that aim to reduce aqueous pollutants.

A density functional study of type I to type II crossover in g-C3N4/CoN4 heterostructure in presence of external perturbation

Herein, we report the impact of external perturbation on the photocatalytic performance of g-C3N4/CoN4 heterojunction and concomitant transition from type-I to type-II. The state-of-the-art theoretical modeling presented here is the first study on dynamic role of strain and electric field on g-C3N4/CoN4 heterojunction and its potential application as a solar-driven water splitting reaction. Utilizing the density functional theory (DFT) calculation, V. N. et al. recently reported the photocatalytic activity of g-C3N4/MN4 (M = Mn, Fe and Co) heterojunction [J. Comput. Chem. 2024, 45, 2518-2529, https://doi.org/10.1002/jcc.2746412] and subsequently established g-C3N4/CoN4 as a type I heterojunction for photocatalytic water splitting reaction [Phys. Chem. Chem. Phys. 2024, 26, 21117–21133]. In the present study, we applied external perturbation in the form of mechanical strain, electric field and evaluated the electronic structure properties of the system along with the detailed examination of concomitant optical and magnetic properties of g-C3N4/CoN4 heterojunction. The switching of photocatalytic feature from type I to type II originates due to the crossover between valence band maxima (VBM) of g-C3N4 and CoN4 in presence of external perturbation. Notably, the resulting system acts as a type II photocatalyst for water splitting reaction while applying compressive (negative) strain of −2 to −6% and an electric field of −0.5 and +0.5 V/Å, respectively. Accumulation of photogenerated electrons and holes separately in g-C3N4 and CoN4 units confirms the perceptible separation of charge carriers and thereby reduces the recombination compared to un-perturbed system. A red-shifted absorption maximum (689 nm), superior charge transfer (0.9e), and clear separation of photogenerated electrons and holes are the origin of enhanced photocatalytic efficiency of g-C3N4/CoN4 heterojunction in the presence of external perturbation. We believe that our work will provide enough evidence to the experimentalists to achieve such a system in practice leading to human-friendly applications.

Investigating the Impact of Stress on the Optical Properties of GaN-MX2 (M=Mo, W; X=S, Se) Heterojunctions Using the First Principles

This study used the first-principles-based CASTEP software to calculate the structural, electronic, and optical properties of heterojunctions based on single-layer GaN. GaN-MX2 exhibited minimal lattice mismatches, typically less than 3.5%, thereby ensuring lattice coherence. Notably, GaN-MoSe2 had the lowest binding energy, signifying its superior stability among the variants. When compared to single-layer GaN, which has an indirect band gap, all four heterojunctions displayed a smaller direct band gap. These heterojunctions were classified as type II. GaN-MoS2 and GaN-MoSe2 possessed relatively larger interface potential differences, hinting at stronger built-in electric fields. This resulted in an enhanced electron–hole separation ability. GaN-MoSe2 exhibited the highest value for the real part of the dielectric function. This suggests a superior electronic polarization capability under an electric field, leading to high electron mobility. GaN-MoSe2 possessed the strongest optical absorption capacity. Consequently, GaN-MoSe2 was inferred to possess the strongest photocatalytic capability. The band structure and optical properties of GaN-MoSe2 under applied pressure were further calculated. The findings revealed that stress significantly influenced the band gap width and light absorption capacity of GaN-MoSe2. Specifically, under a pressure of 5 GPa, GaN-MoSe2 demonstrated a significantly narrower band gap and enhanced absorption capacity compared to its intrinsic state. These results imply that the application of stress could potentially boost its photocatalytic performance, making it a promising candidate for various applications.

Dual-active-group co-modification of BiOBr for boosting photocatalytic CO2 reduction coupled with ciprofloxacin oxidation

Coupling CO2 photoreduction with ciprofloxacin (CIP) oxidation presents a promising strategy for achieving not only the complete utilization of photoexcited carriers but also the win–win goals of energy conversion and environmental remediation. In this study, we utilized an aminated BiOBr catalyst with surface hydroxyl groups (NH2/BOB–OH) for efficient photocatalytic CO2 reduction coupled with CIP oxidation. In this process, hydroxyl (OH) and amino groups (NH2) adsorbed and activated CIP (an organic pollutant) and CO2 molecules, respectively, promoting the overall photocatalytic redox activity. Remarkably, 0.5NH2/BOB–OH exhibited excellent photocatalytic redox performance for CO2 reduction coupled with CIP oxidation, with the CO yield and CIP degradation efficiency being 6.85 and 1.08 times higher, respectively, than those achieved using BiOBr without any active groups. Moreover, a series of in situ experimental characterizations and theoretical simulations revealed that these two opposing active groups not only accelerated carrier separation but also boosted the surface reactivity of the catalyst. These findings provide helpful insights into the dual-active-group functionalization of semiconductors, leading to their high photoredox activity for energy conversion along with environmental remediation.

Sonochemical preparation of powerful S-scheme Zr(HPO4)2/g-C3N4 heterojunction for photocatalytic degradation of rhodamine B under natural solar radiations

An effective Zr(HPO4)2/g-C3N4 S-scheme heterojunction was synthesized by sonochemical coupling of Zr(HPO4)2 nanoparticles as an oxidative photocatalyst [EVB = +3.0 eV] with g-C3N4 nanosheets as an effective reductive photocatalyst [ECB = −1.25 eV] for photocatalytic degradation of rhodamine B dye under natural solar radiation of 1000 W power. The physicochemical properties of the as-synthesized heterojunctions were investigated by X-ray diffraction [XRD], N2-adsorption-desorption isotherm, diffuse reflectance spectrum [DRS], photoluminescence [PL], scanning electron microscope [SEM], X-ray photoelectron spectroscope [XPS], and high resolution transmission electron microscope [HRTEM]. The experimental results implied the agglomeration of Zr(HPO4)2 nanoparticles on g-C3N4 sheets which reduced the specific surface area of the solid specimen from 88 to 21 m2/g. The significant increase in the photocatalytic degradation rate of RhB dye with introducing Zr(HPO4)2 nanoparticles implied that Zr(HPO4)2 plays a crucial role in reducing the band gap energy and remarkable increasing in the rate of electron-hole separation. The photocatalytic experiments implied that incorporation of 5 wt% Zr(HPO4)2 on g-C3N4 sheets destroyed 98 % of RhB dye during 3 h of light illumination with pseudo-first-order rate of 0.048 min−1. The remarkable enhancement in the photocatalytic performance of Zr(HPO4)2/g-C3N4 heterojunctions was ascribed to successful generation of an effective S-scheme heterojunction with strong redox power, utilizing of both hydroxyl and superoxide radicals in the degradation process and limiting the electron-hole recombination rate. Based on scavenger experiments and terephthalic acid PL analysis, the S-scheme pathway was chosen as the proposed mechanism for photocatalytic charge transfer. The as-synthesized Zr(HPO4)2/g-C3N4 heterojunction with exceptional redox power is considered a novel candidate for destructing organic pollutants that exist in industrial wastewater.

Fabrication of rGO-Bridged TiO2/g-C3N4 Z-Scheme Nanocomposites via Pulsed Laser Ablation for Efficient Photocatalytic CO2 Reduction.

Highly efficient photocatalysts can be fabricated using favorable charge transfer nanocomposite channel structures. This study adopted pulsed laser ablation in liquid (PLAL) to obtain rGO-bridged TiO2/g-C3N4 (rGO-TiO2/g-C3N4) photocatalytic Z-scheme without the need for noble metals. In addition to evaluating the resulting nanocomposite (comprising rGO nanosheets, TiO2 nanotubes, and g-C3N4 nanosheets) CO2 reduction effectiveness, its chemical, morphological, structural, and optical characteristics were examined using various analytical techniques. The findings revealed a synergistic interaction between g-C3N4 and TiO2, suggesting the presence of unique interfacial bonding, as well as enhanced visible light absorption. Notably, the ternary rGO-TiO2/g-C3N4 Z-scheme exhibits an excellent photocatalytic performance by photocatalytically converting CO2 into CO and CH4, with 81 % selectivity towards the CO and 1.91 % apparent quantum efficiency at 420 nm. Thus, the findings can pave the way for various Z-scheme systems in wide photocatalytic applications.

ZnO@In2O3 Core-Shell Heterojunctions Constructed With ZIF-8 and MIL-68 (In) for Improving Photogenerated Carrier Transfer Process.

The realization of fast carrier transport can effectively enhance photocatalytic performance. A core-shell structure of ZnO and In2O3 is successfully constructed by using MIL-68 (In) and ZIF-8 as a substrate, forming a heterojunction. This MOF-derived core-shell heterojunction inherits the advantages of ZIF-8, with pores facilitating carriers transfer to the surface for reactions and a large specific surface area providing more active sites. This Z-scheme heterojunction of ZnO and In2O3 can effectively separate and improve the utilization of photogenerated carriers. The well-designed interface of the core-shell structure achieves the rapid transfer of photogenerated carriers. The photocatalytic degradation capability of ZnO@ In2O3 is enhanced by the synergistic effect of Z-scheme heterojunction and core-shell structure. This work provides insight into the investigation of constructing core-shell heterojunctions.

Hollow Nanobox‐Shaped Cu2‐xS@ZnxCd1‐xS Heterojunction by Light Multireflection with Z‐Scheme Mechanism for Enhanced Photocatalytic Hydrogen Production

AbstractAchieving efficient spatial photoinduced charge separation and light utilization for improving the high photocatalytic activity is still a major obstacle. Here, a Cu2‐xS@ZnxCd1‐xS (Cu2‐xS@ZnCdS) heterojunction is reported featuring a distinctive core–shell hollow nanobox structure. The Cu2‐xS@ZnxCd1‐xS exhibits high photocatalytic activity in hydrogen evolution reaction (HER) at the rate of 8175 µmol∙g−1∙h−1 under visible light irradiation, outperforming pristine ZnCdS nanoparticles and Cu2‐xS hollow nanoboxes. The remarkable activity and outstanding stability of Cu2‐x@ZnCdS are attributed to the development of robust interfacial electric fields, and improved light multireflection absorption efficiency as well as the Z‐scheme mechanism. The electron paramagnetic resonance (EPR) and in situ X‐ray photoelectron spectroscopy (XPS) measurements gave the direct evidence of the formation of the Z‐scheme, which maintained the high redox potentials of each ZnCdS and Cu2‐xS. This study gives the guideline for the design of heterojunction with the Z‐scheme mechanism, leading to the high photocatalytic performance and remarkable stability.

In-situ and ex-situ preparation of Bi2S3 on the BiVO4/TiO2 to construct Bi2S3/BiVO4/TiO2 heterojunction for efficient Cr(VI) reduction

The environmentally friendly and rapid removal of hexavalent chromium (Cr(VI)) from wastewater has garnered significant attention, driven by the severe acute toxicity and carcinogenic properties associated with Cr(VI). The design and synthesis of heterojunctions are recognized as effective solutions for enhancing the photocatalytic performance of TiO2 based materials. BiVO4/TiO2 and Bi2S3/BiVO4/TiO2 composite films (BVT) were prepared via a simple hydrothermal method. The influence of Bi2S3 preparation methods (In-situ and Ex-situ) on the morphology, structure and properties of BVT was studied. The relative crystallinity of TiO2, BiVO4/TiO2, BVT(In-situ) and BVT(Ex-situ) were 50 %, 62 %, 72 % and 92 %, respectively. SEM shows that the morphology of Bi2S3 in BVT(In-situ) was nanoribbon and that of Bi2S3 in BVT(Ex-situ) was radioactive sphere. Compared with pure TiO2 and BiVO4/TiO2, the light absorption range of BVT composite material has been expanded from the ultraviolet light region to the visible region, the bandgap has been significantly narrowed, and the photocurrent density has been increased. The BVT(In-situ) shows stronger photoelectrical performance and reduction efficiency of Cr (VI) compared to BVT(Ex-situ), reaching 93.9 %. The photocatalytic reaction rate of BVT(In-situ) and BVT(Ex-situ) are 0.0291 min−1 and 0.0266 min−1, respectively. Density functional theory (DFT) calculations indicate that the work function of BiVO4 is higher than that of Bi2S3, and electrons will transfer from Bi2S3 to BiVO4 at the heterojunction interface. The BVT(In-situ) heterojunction constructed in this experiment greatly improves the separation and transport efficiency of photo-generated carriers, laying the foundation for the wide application of BVT heterojunction in the field of optoelectronics and providing a strategy for photocatalytic reduction of Cr(VI). The BVT(In-situ) with FTO conductive glass, it also can be applied to photovoltaic fields such as solar cells, photocatalysis and photodetectors.

Nd3+ induces three-dimensional hierarchical rosette-shaped Bi3O4Br to generate abundant oxygen vacancies for enhanced photocatalytic activity

Three-dimensional hierarchical rosette-shaped Bi3O4Br has been successfully prepared by a one-step hydrothermal method for the first time, in which the doping of Nd3+ into the matrix of Bi3O4Br induces abundant oxygen vacancies and triggers energy-band hybridization to produce new dopant levels, which can efficiently receive photo-excited electrons and inhibit the complexation of photogenerated carriers. Impressively, the doped energy levels act as “springboards” for photogenerated electron jumps, exacerbating the inhomogeneity of charge distribution and accelerating charge separation. In addition, the fine-tuning of Nd3+ improves the band structure and photocatalytic performance of Nd/Bi3O4Br. Notably, the unique 3D rosette-like Bi3O4Br could enhance the adsorption capacity of the catalyst and provide more opportunities for the introduction of Nd3+ to induce the generation of abundant oxygen vacancies. Both experimental and density functional theory (DFT) results reveal the synergistic effect of energy band hybridization and oxygen vacancies. In addition, comparative experiments showed that Nd/Bi3O4Br enhanced the maximum removal efficiency of heavy metal mercury by 29.66 % relative to Bi3O4Br under visible light. The present work reveals the reaction mechanism of photocatalytic oxidation for mercury removal, which provides a new direction for realizing energy conversion and environmental purification in the future.

Constructing dual-channel carrier transport in AgBr/BiOBr/Ag3PO4 heterojunctions for enhanced photocatalytic NO removal

Efficient and stable photocatalysts are indispensable for effectively reducing nitrogen oxide (NOx) emissions. This study presents a facile method for synthesizing AgBr/BiOBr/Ag3PO4 composites and investigates their application in photocatalytic NO removal. The optimized composite exhibited notable performance, achieving 54.95 % removal of NO (approximately 568 ppb reduced to 256 ppb) under visible light irradiation, which is about 1.6 and 2.0 times higher than single Ag3PO4 (34.95 %) and BiOBr (28.01 %), respectively. Comprehensive physicochemical characterization highlighted enhancements in light absorption and the generation of reactive radicals within the AgBr/BiOBr/Ag3PO4 composite. The favorable electronic structure, characterized by well-aligned redox band positions, facilitated efficient dual carrier transport routes, thereby promoting the separation of photo-generated charge carriers. Additionally, in-situ DRIFTS analysis revealed that the composite facilitated the conversion of intermediates into nitrates during the NO purification process. This work contributes valuable insights into designing and preparing of ternary heterojunction photocatalysts with dual carrier transport channels, advancing strategies for achieving superior photocatalytic performance.

Preparation and Photocatalytic Performance of In2O3/Bi2WO6 Type II Heterojunction Composite Materials.

Bismuth-based photocatalytic materials have been widely used in the field of photocatalysis in recent years due to their unique layered structure. However, single bismuth-based photocatalytic materials are greatly limited in their photocatalytic performance due to their poor response to visible light and easy recombination of photogenerated charges. At present, constructing semiconductor heterojunctions is an effective modification method that improves quantum efficiency by promoting the separation of photogenerated electrons and holes. In this study, the successful preparation of an In2O3/Bi2WO6 (In2O3/BWO) II-type semiconductor heterojunction composite material was achieved. XRD characterization was performed to conduct a phase analysis of the samples, SEM and TEM characterization for a morphology analysis of the samples, and DRS and XPS testing for optical property and elemental valence state analyses of the samples. In the II-type semiconductor junction system, photogenerated electrons (e-) on the In2O3 conduction band (CB) migrate to the BWO CB, while holes (h+) on the BWO valence band (VB) transfer to the In2O3 VB, promoting the separation of photoinduced charges, raising the quantum efficiency. When the molar ratio of In2O3/BWO is 2:6, the photocatalytic degradation degree of rhodamine B (RhB) is 59.4% (44.0% for BWO) after 60 min illumination, showing the best photocatalytic activity. After four cycles, the degradation degree of the sample was 54.3%, which is 91.4% of that of the first photocatalytic degradation experiment, indicating that the sample has good reusability. The XRD results of 2:6 In2O3/BWO before and after the cyclic experiments show that the positions and intensities of its diffraction peaks did not change significantly, indicating excellent structural stability. The active species experiment results imply that h+ is the primary species. Additionally, this study proposes a mechanism for the separation, migration, and photocatalysis of photoinduced charges in II-type semiconductor junctions.

Photocatalytic performance of pristine NiO and Ni6MnO8 nanopowders in degradation of Rose Bengal dye.

Effective tuning of bandgap of transition metal oxides is a promising approach in improving their photocatalytic activity towards organic pollutant removal from water. The present paper describes synthesis of nickel oxide and Ni6MnO8 nanopowders by simple hydrothermal technique. During the synthesis of nickel oxide by hydrothermal process, addition of Mn source resulted in the formation of Ni6MnO8. X-ray diffraction analysis has confirmed the formation of nickel oxide and Ni6MnO8 both having cubic structures. The average crystallite size decreases from 20 to 12nm on increasing Mn source concentration during the synthesis of nickel oxide. Rectangular, hexagonal, and triangular faceted structures are revealed from the scanning electron microscopic images. HRTEM also indicated formation of cubical shaped structure with average sizes of 32 and 21nm for pristine NiO and Ni6MnO8 nanopowders. In the case of Ni6MnO8 nanopowder, inter-connected cubes are seen. Modification in Ni6MnO8 nanopowder is found to display multiple optical band gaps at 1.21, 1.82, and 2.65eV. The formation of Ni6MnO8 phase was further confirmed by XPS studies due to the presence of + 4 oxidation state of Mn. The photocatalytic properties of synthesized nickel oxide and Ni6MnO8 nanopowders are measured by using Rose Bengal dye under UV illumination. Enhancement in the photocatalytic activity is noticed in the case of Ni6MnO8 nanopowder as compared to nickel oxide nanopowder. Nearly 90% dye degradation is observed on utilizing Ni6MnO8 nanopowder.

Magnetic and visible light-induced novel green synthesized magnetic Co3O4 photocatalysts via sunflower seed meal extract for anionic and cationic dye removal by adsorption assisted photocatalytic degradation

This study was aimed at the preparation of m-Co3O4 NPs (magnetic Co3O4 nanoparticles) from sunflower seed meal (SFSM) which is the waste of sunflower seed oil factories, and their application as a photocatalyst for the adsorption assistant photocatalysis degradation of methylene blue (MB), and direct yellow-50 (DY-50) under the visible irradiations. Also, the photocatalytic performance of m-Co3O4 NPs was evaluated in synthetic wastewater. The produced m-Co3O4 NPs were ferromagnetic with a saturation magnetization value of 4.3 emu g−1 and the degradation of cationic MB and anionic DY-50 dyes by 100% and 93% in 20 min and 35 min, respectively, by adsorption-assisted photocatalytic process under visible light was achieved. The reactions were found to be pseudo-second-order equation for the adsorption-assisted photocatalytic process for both dyes. The photocatalytic activity of m-Co3O4 NPs decreased slightly even after five repeated cycles. These results show that the m-Co3O4 NPs can be used successfully in dye treatment in wastewater with their adsorption-assisted photocatalytic properties, activation by visible light, magnetic separability, and low-cost production.

Boosting the Quantum Efficiency of Ionic Carbon Nitrides in Photocatalytic H2O2 Evolution via Controllable n → π* Electronic Transition Activation.

Hydrogen peroxide (H2O2) is a crucial chemical used in numerous industrial applications, yet its manufacturing relies on the energy-demanding anthraquinone process. Solar-driven synthesis of H2O2 is gaining traction as a promising research area, providing a sustainable method for its production. Herein, a controllable activation of n → π* electronic transition is presented to boost the photocatalytic H2O2 evolution in ionic carbon nitrides. This enhancement is achieved through the simultaneous introduction of structural distortions and defect sites (─C ≡ N groups and N vacancies) into the KPHI framework. The optimal catalyst (2%Ox-KPHI) reached an apparent quantum yield of 41% at 410nm without the need for any cocatalysts, outperforming most previously reported carbon nitride-based photocatalysts. Extensive experimental characterizations and theoretical calculations confirm that a corrugated configuration and the presence of defects significantly broaden the light absorption profile, improve carrier separation and migration, promote O2 adsorption, and lower the energy barriers for H2O2 desorption. Transient absorption spectroscopy indicates that the enhanced photocatalytic performance of 2%Ox-KPHI is largely attributed to the preferential migration of electrons at defect sites over extended timescales, following the diffusion of geminate carriers across the PHI sheets.