Visible-light Photocatalytic Efficiency Research Articles

Enhanced Visible-Light Photocatalytic Degradation Efficiency of Ce4+ -Doped ZrO2/ZnO Nanocomposites Fabricated by a Simple Hydrothermal Method

Enhanced Visible-Light Photocatalytic Degradation Efficiency of Ce4+ -Doped ZrO2/ZnO Nanocomposites Fabricated by a Simple Hydrothermal Method

Fabrication of a novel microflower BiOCl composite incorporated with rosemary powder for enhanced oxygen vacancies and visible-light photocatalytic efficiency

Incorporating metallic or nonmetallic compounds is a promising method for enhancing the oxygen vacancies (OVs), charge transport, and visible light absorption of a bismuth oxychloride (BiOCl) semiconductor. This research aims to improve the properties of BiOCl by incorporating rosemary powder (RPC). BiOCl photocatalysts with enhanced OVs were synthesized through the addition of 1–4 wt% of RPC using a one-pot solvothermal process. The addition of 3 % RPC resulted in the formation of very small particles on the BiOCl lamellar structures, which were aligned with the (002) plane of carbon quantum dots (CQDs). The uniformly distributed CQDs transformed the BiOCl microstructure from a two-dimensional lamellar structure to a three-dimensional floral structure, leading to an increased surface area and pore volume. The incorporation of RPC enhanced the visible light absorption capacity of BiOCl. The carbon atoms in RPC readily attach to oxygen atoms in the Bi-O bond, disrupting the Bi-O lattice bond and forming OVs. The addition of RPC contributed to a higher number of OVs, which impacted both the energy difference between the valence and conduction bands and their locations. This resulted in better charge transfer and enhanced active species formation. The 3 %-RPC-BOC photocatalyst had the highest efficiency, achieving a 98 % degradation of rhodamine B (RhB) and a 45 % removal of organic carbon within 48 min under visible light. This composite also had excellent stability and reusability, as its crystal structure remained unaltered even after conducting 7 cycles. The primary active species of 3 %-RPC-BOC system is the superoxide radical (·O2-), while the hydroxyl radical (·OH) and hole (h+) operate as minor active species. Additionally, the 3 %-RPC-BOC achieved a high tetracycline (TC) removal rate of 82.1 %, which is 2.21 times higher than that of pure BiOCl.

Facile synthesis of a novel CeCO3OH@(H/C–CdS) catalyst with synergistic effect of heterophase junction and heterojunction for enhanced visible-light photocatalytic degradation efficiency at room temperature

A new CeCO3OH@(hexagonal/cubic phases–CdS) (CeCO3OH@(H/C–CdS)) composite catalyst was facilely synthesized by a simple microinjection titration–stirring method, in which CdS nanoparticles were dispersed on the surface of CeCO3OH nanolines. The optimal conditions for the preparation of composite catalysts with high photocatalytic performance were determined by single-factor experiments and response surface experiments. Under these conditions, the degradation rate of 30 mL 2.000 g/L rhodamine B (Rh B) by CeCO3OH@(H/C-CdS) in a photocatalytic reaction for 1 h at 25 °C was up to 86.81 % and its degradation rate in a photocatalytic reaction for 150 min was up to 99.62 %. The degradation rate could be maintained above 80 % even after six times recycling. Especially, the photocatalytic degradation efficiency of 2.000 g/L Rh B on the composite catalyst under sunlight and at room temperature for 30 min reached 97.66 %. Meanwhile, the large size of CeCO3OH considerably alleviated the agglomeration of CdS, providing more adsorption and active sites for visible light-mediated degradation of Rh B. Importantly, the Z-scheme charge transfer realized by CdS and CeCO3OH enhanced the efficient separation of photogenerated electrons and holes, and successfully inhibited the recombination of photogenerated electrons with holes. At the same time, owing to the low energy band difference between the two phases of CdS, charge was transferred between the hexagonal and cubic phases, leaving more effective photogenerated charge to participate in the degradation of Rh B. The synergism of the heterophase junction and heterojunction and the presence of oxygen and sulfur vacancies considerably enhanced the degradation performance of the catalyst. Thus, this study provides a new strategy for the modification and enhanced visible-light catalysis performance of CdS-based catalysts.

Chitosan-mediated tailoring of cadmium sulphide nanoparticle: Synthesis, properties, and interactive mechanisms

This study explores the synergistic effects of chitosan-coated cadmium sulphide (CdS) nanoparticles (NPs) at varying concentrations on their structural, optical, and photocatalytic properties. CdS NPs are known for their promising photocatalytic potential, but their practical application often requires stability enhancement and reduced toxicity. Chitosan, a natural biopolymer, offers unique advantages such as biocompatibility and heavy metal adsorption capabilities, making it an attractive candidate for surface modification of CdS NPs. Our investigation reveals that chitosan-coated CdS NPs exhibit concentration-dependent changes in their crystalline structure, bandgap energy, particle size, and vibrational characteristics. Notably, CdS NPs synthesized with 1.5 g chitosan concentration display the smallest bandgap and particle size, suggesting optimal photocatalytic activity. This research provides valuable insights into tailoring CdS NPs for efficient visible light photocatalysis, with implications in environmental remediation and energy conversion.

Polylactic acid electrospun membrane loaded with cerium nitrogen co-doped titanium dioxide for visible light-triggered antibacterial photocatalytic therapy.

Wound infection caused by multidrug-resistant bacteria poses a serious threat to antibiotic therapy. Therefore, it is of vital importance to find new methods and modes for antibacterial therapy. The cerium nitrogen co-doped titanium dioxide nanoparticles (N-TiO2, 0.05Ce-N-TiO2, 0.1Ce-N-TiO2, and 0.2Ce-N-TiO2) were synthesized using the hydrothermal method in this study. Subsequently, electrospinning was employed to fabricate polylactic acid (PLA) electrospun membranes loaded with the above-mentioned nanoparticles (PLA-N, PLA-0.05, PLA-0.1, and PLA-0.2). The results indicated that cerium and nitrogen co-doping tetrabutyl titanate enhanced the visible light photocatalytic efficiency of TiO2 nanoparticles and enabled the conversion of ultraviolet light into harmless visible light. The photocatalytic reaction under visible light irradiation induced the generation of ROS, which could effectively inhibit the bacterial growth. The antibacterial assay showed that it was effective in eliminating S. aureus and E. coli and the survival rates of two types of bacteria under 30 min of irradiation were significantly below 20% in the PLA-0.2 experimental group. Moreover, the bactericidal membranes also have excellent biocompatibility performance. This bio-friendly and biodegradable membrane may be applied to skin trauma and infection in future to curb drug-resistant bacteria and provide more alternative options for antimicrobial therapy.

Artificial Photosynthases: Single-Chain Nanoparticles with Manifold Visible-Light Photocatalytic Activity for Challenging "in Water" Organic Reactions.

Photocatalyzed reactions of organic substances in aqueous media are challenging transformations, often because of scarce solubility of substrates and catalyst deactivation. Herein, we report single-chain nanoparticles, SCNPs, capable of efficiently catalyzing four different "in water" organic reactions by employing visible light as the only external energy source. Specifically, we decorated a high-molecular-weight copolymer, poly(OEGMA300-r-AEMA), with iridium(III) cyclometalated complex pendants at varying content amounts. The isolated functionalized copolymers demonstrated self-assembly into noncovalent, amphiphilic SCNPs in water, which enabled efficient visible-light photocatalysis of two reactions unprecedentedly reported in water, namely, [2 + 2] photocycloaddition of vinyl arenes and α-arylation of N-arylamines. Additionally, aerobic oxidation of 9-substituted anthracenes and β-sulfonylation of α-methylstyrene were successfully carried out in aqueous media. Hence, by merging metal-mediated photocatalysis and SCNPs for the fabrication of artificial photoenzyme-like nano-objects─i.e., artificial photosynthases (APS)─our work broadens the possibilities for performing challenging "in water" organic transformations via visible-light photocatalysis.

Effective Interfacing of Surface Homojunctions on Chemically Identical g-C3N4 for Efficient Visible-Light Photocatalysis without Sacrificial Agents.

Developing efficient homojunctions on g-C3N4 promises metal-free photocatalysis to realize truly sustainable artificial photosynthesis. However, current designs are limited by hindered charge separation due to inevitable grain boundaries and random formation of ineffective homojunctions embedded within the photocatalyst. Here, efficient photocatalysis is driven by introducing effective surface homojunctions on chemically and structurally identical g-C3N4 through leveraging its size-dependent electronic properties. Using a top-down approach, the surface layer of bulk g-C3N4 is partially exfoliated to create sheet-like g-C3N4 nanostructures on the bulk material. This hierarchical design establishes a subtle band energy offset between the macroscopic and nanoscopic g-C3N4, generating homojunctions while maintaining the chemical and structural integrities of the original g-C3N4. The optimized g-C3N4 homojunction demonstrates superior photocatalytic degradation of antibiotic pollutants at >96% efficiency in 2h, even in different real water samples. It achieves reaction kinetics (≈0.041min-1) up to fourfold better than standalone materials and their physical mixture. Mechanistic studies highlight the importance of the unique design in boosting photocatalysis by effectively promoting interfacial photocarrier manipulation and utilization directly at the point-of-catalysis, without needing co-catalysts or sacrificial agents. This work presents enormous opportunities for developing advanced and green photocatalytic platforms for sustainable light-driven environmental, energy, and chemical applications.

Green synthesis and characterization of α-Mn2O3 nanoparticles for antibacterial activity and efficient visible-light photocatalysis

In this study, green synthesis, characterizations, photocatalytic performance, and antibacterial applications of α-Mn2O3 nanoparticles are reported. The synthesized nanoparticles were characterized by Fourier transform infrared spectroscopy (FT-IR), powder X-ray diffraction (XRD), transmission electron microscope (TEM), Scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), Brunauer Emmett Teller (BET), Electrochemical Impedance Spectroscopy (EIS), Photoluminescence (PL), and Differential reflectance spectroscopy (DRS) analysis. The investigation verified that the α-Mn2O3 nanoparticles possessed a cubic structure, with a crystallite size of 23 nm. The SEM and TEM techniques were used to study the nanoscale morphology of α- Mn2O3 nanoparticles, which were found to be spherical with a size of 30 nm. Moreover, the surface area was obtained as 149.9 m2 g−1 utilizing BET analysis, and the band gap was determined to be 1.98 eV by DRS analysis. The photocatalysis performance of the α-Mn2O3 NPs was evaluated for degrading Eriochrome Black T (EBT) dye under visible light and degradation efficiency was 96% in 90 min. The photodegradation mechanism of EBT dye was clarified with the use of radical scavenger agents, and the degradation pathway was confirmed through Liquid Chromatography–Mass Spectrometry (LC–MS) analysis. Additionally, the produced nanoparticles could be extracted from the solution and continued to exhibit photocatalysis even after five repeated runs under the same optimal conditions. Also, the antibacterial activity of green synthesized α-Mn2O3 nanoparticles was investigated by using the broth microdilution method towards Enterococcus faecalis ATCC 29212 (Gram-positive), Staphylococcus aureus ATCC 29213 (Gram-positive), Salmonella typhimurium ATCC 14028 (Gram-negative), Klebsiella pneumoniae ATCC 7881 (Gram-negative), Escherichia coli ATCC 25922 (Gram-negative), Proteus mirabilis ATCC 7002 (Gram-negative), and Pseudomonas aeruginosa ATCC 27853 (Gram-negative) bacterial strains.

Preparation and characterization of ZnO/CuO nanocomposites thin films for highly efficient visible-light photocatalysis of acriflavine dye

Chemical bath deposition (CBD) was used to grow ZnO nanorods on glass substrates. Grown ZnO nanorods are dipped in a copper nitrate trihydrate [Cu(NO3)2.3 H2O] solution at 90 °C for 30 min before being annealed at 400 °C for 1 h to convert Cu2+ ions to CuO nanoparticles, forming a ZnO/CuO thin films nanocomposite. Images obtained from a Field Emission Scanning Electron Microscope (FESEM) indicated that the ZnO structure consisted of nanorods coated in CuO nanoparticles. The optical absorption of both ZnO NRs and ZnO/CuO nanocomposites thin films was strongly edged, with an energy gap of 3.26 and 3.21 eV, respectively. The photodegradation rate of the manufactured ZnO NRs and ZnO/CuO nanocomposites thin films against Acriflavin dye was investigated at room temperature under varying pH conditions and period exposure to visible light. The rate of photodegradation of the dye was increased by increasing the time it was exposed to light and/or the pH of the solution. The photodegradation rates for AFN dye under visible light irradiation ranged from 36% to 100% as the pH value was increased from 4 to 10, and from 78% to 66% at a pH value of 12 and reduced to 78% at a pH value of 12 after 330 min of irradiation. Furthermore, the trapping experiments of reactive species for Acriflavin dye degradation by ZnO/CuO nanocomposites photocatalysts were also carried out

Enhanced visible-light photocatalytic degradation efficiency of Ce3+-doped ZnO nanoparticles synthesized by sol-gel method

While Ce3+-doped ZnO nanoparticles have been extensively explored for UV light photocatalytic applications, harnessing their efficacy for visible light photocatalysis remains a significant challenge. This study demonstrates the outstanding degradation efficiency under visible light of Ce3+-doped ZnO nanoparticles synthesized via the sol-gel route. At lower concentrations (<3 mol%), Ce3+ ions seamlessly substitute Zn2+ ions within the ZnO lattice, while at higher dopant levels (≥3 mol%), the formation of CeO2 nanoparticles on the ZnO surface becomes an additional noteworthy feature. This unique combination in highly Ce3+-doped ZnO nanoparticles leads to the creation of Ce-impurity states (e.g., Ce3+/Ce4+) within the ZnO structure, effectively separating electrons and holes. Consequently, the generation of superoxide radical anions is enhanced, boosting the remarkablely DB71 dye degradation efficiency (>90%) of all highly Ce3+-doped ZnO samples (≥3 mol%) in comparison with pristine and lightly Ce3+-doped ZnO samples (<3 mol%). In all highly Ce3+-doped ZnO samples, 5-mol% doped sample shows the highest DB71 degradation efficiency of 98.4%. This remarkable achievement is observed when utilizing 0.1 g of 5-mol% doped sample, 50 mg/L of initial DB71 concentration, pH of 5, and notablely under visible light irradiation. Furthermore, the DB71 degrading efficiency of ZnO:5%Ce3+ maintains an impressive 90.3% over five cycles from its initial value of 98.4%, underscoring the potential of ZnO:Ce3+ as a promising photocatalyst for practical wastewater treatment.

Excellent visible-light photocatalytic hydrogen production efficiency: Hollow-structured TiO2/CdS/Au or hollow-structured TiO2/Au/CdS ternary heterojunction nanocomposites?

Two ternary heterojunction composites, namely hollow-structured TiO2/CdS/Au and hollow-structured TiO2/Au/CdS, were successfully synthesized by preparing hollow-structured TiO2 first, followed by the deposition of Au and CdS (with different deposition sequences), respectively. In these two composites, hollow-structured TiO2 nanotubes provide 1D structure with large specific area, which facilitate the immobilization of CdS and Au nanoparticles and the transfer of electrons. CdS is visible-light responsive and Au nanoparticles can improve photocatalytic efficiency by the formation of schottky barrier and surface plasmon resonance effect (SPR). The structures and phases, morphologies, surface and optical properties of the two composites were systematically characterized. TiO2/CdS/Au ternary heterojunction composite has efficient light absorption ability and excellent performances in photocatalytic hydrogen generation (up to 3600 μmol h−1 g−1), which is more than 4 times higher than that of TiO2/Au/CdS (800 μmol h−1 g−1). Therefore, in this way, we present a promising strategy to construct hybrid photocatalysts for hydrogen production.

Self-grown Ag2O nanoparticles on Ag-NASICON material for efficient visible light photocatalysis

Ag-containing semiconductors have gained great attention due to their outstanding visible light-responsive photocatalytic properties. In the current work, silver oxide (Ag2O) nanoparticles were in situ self-grown on the surface of AgZr2(PO4)3 NASICON-type material using sodium hydroxide-assisted precipitation to form an Ag2O/Ag1-xNaxZr2(PO4)3 nanocomposite. The crystalline structures, morphological observations, elemental composition, and optical properties of the prepared product were carried out using various characterization methods. The photocatalytic performance of Ag2O/Ag1-xNaxZr2(PO4)3 has then been explored in the decomposition of methyl orange (MO) wastewater pollutant under visible light. The obtained photocatalyst exhibited excellent decomposition efficiency (95.08 %, k = 0.0303 min−1) for MO removal within 60 min. In addition, the prepared nanocomposite exhibited proper reusability even after five successive cycles without any significant loss in photocatalytic activities. Furthermore, a simple catalyst regeneration strategy based on hydrogen peroxide (H2O2) was adopted, revealing that the spent photocatalyst can achieve nearly total self-regeneration to the initial AgZr2(PO4)3 material.

One-pot synthesis of defect engineered carbon nitride for highly efficient visible light photocatalysis

Solvothermally prepared defect-engineered CN samples, featuring surface cyano groups and carbon doping, enhance light absorption and charge separation, significantly improving visible light photodegradation.

Bio-inspired synthesis of N-doped TiO2/C nanocrystals using jellyfish mucus with high visible-light photocatalytic efficiency.

Non-metal doping of titanium dioxide (TiO2) has been widely investigated, because it can facilely improve the optical response of TiO2 under visible light excitation in environmental pollution treatments. In the ongoing efforts, however, little consideration has been given to the use of harmful marine organisms as dopants. Here, we employed the natural mucus proteins of the large harmful jellyfish Aurelia coerulea and Nemopilema nomurai, which have frequently bloomed in East Asian marginal seas in recent decades, to synthesize mesoporous nitrogen-doped TiO2 nanocrystals modified with carbon (N-TiO2/C) by a simple hydrothermal method. These nanocrystals were composed of predominantly anatase phase and a small amount of brookite phase TiO2. Their mesoporous structures changed with the variation of the volume ratio of jellyfish mucus added to tetrabutyl titanate (TBT). At the same ratio, larger surface area and pore volume but smaller pore size were observed in N-TiO2/C nanocrystals from N. nomurai rather than A. coerulea. Nitrogen was determinately doped into the lattice of the prepared nanocrystals and the carbon species were modified on their surfaces, which narrowed the band gap, facilitated the separation of photogenerated electron-hole pairs and favored the absorption of visible light, thus improving their visible light photocatalytic activity. The photocatalytic degradation efficiency of Rhodamine B (RhB) under visible light irradiation first increased and then decreased with the gradual increase of the volume ratio of jellyfish mucus proteins to TBT. The maximum reached 97.52% in 20 min from N-TiO2/C nanocrystals synthesized using N. nomurai mucus at the volume ratio of 4 : 1, which showed a remarkably strong visible light absorption, lower band gap energy and smaller electron transfer resistance. These N-TiO2/C nanocrystals also had a relatively stable crystal structure in multiple degradation reactions. The main active species including superoxide radicals (˙O2 -), photogenerated holes (h+) and hydroxyl radicals (˙OH) were found to play a major role in the degradation process of RhB. This study highlights the potential high-value reapplication of harmful jellyfish mucus as a natural organic matrix in fabricating advanced materials with optimized functional properties.

Harnessing iron-rich biochar boosted single crystalline Co2VO4 nano-hexagons: A green photo-Fenton catalyst for rifampicin remediation and byproduct toxicity evaluation

A novel cation-substituted transition metal oxide nano-semiconductor was developed for efficient visible light photocatalysis. This nanocomposite (NCs) was created by immobilizing well-defined single crystalline Co2VO4 2D nano-hexagons onto a mesoporous biochar matrix, derived from philodendron plants. The Co2VO4 nanoparticles (NPs) were synthesized using a biologically assisted method employing an ornamental plant, L. delavayanum. Remarkably, the resultant NCs exhibited exceptional photocatalytic activity, achieving 99% degradation efficiency of pharmaceutical pollutant rifampicin (RIF), and merely 1.8% of total organic carbon (TOC) left as residues post-photocatalytic degradation. The influence of pH (optimal at 8), NCs and RIF concentration, and presence of ions was studied and the system worked effectively in a wide range of environment. The coupling of biochar resulted in a greater narrowing of the bandgap of Co2VO4 and thus extending the working range under visible light. A plausible mechanism assisted with photo-Fenton process is outlined based on the support of extensive characterization carried out to elucidate the NCs properties along with the results of scavenging experiments. The NCs performance retained over 98% efficiency even after six consecutive reusing cycles. The present study underscores the potential of the prepared NCs as a robust and effective solution for environmental pollutant removal, with its unique composition and synergistic photo-Fenton reaction contributing to its outstanding photocatalytic performance.

Efficient visible-light photocatalysis of chloramphenicol using novel engineered biochar-based Ti-doped Bi2WO6 composite: Mechanisms, degradation pathways, and applications

A novel engineered biochar (ACB)-based Ti-doped Bi2WO6 composite (Ti-Bi2WO6@ACB) was synthesized via a one-step hydrothermal reaction for the efficient degradation of chloramphenicol (CAP) and extensive environmental applications. Multiple characterization techniques, CAP degradation effects, total organic carbon (TOC) removal, effects of environmental factors, recycling tests, actual wastewater treatment, enhancement strategies, and disinfection effects were systematically evaluated. It was found that Ti-Bi2WO6@ACB is a Ti3+ self-doped TiO2/Bi2WO6/ACB ternary heterogeneous photocatalyst. The introduction of ACB and Ti doping enhanced the elemental composition, oxygen-containing functional groups, defect structure (oxygen vacancies), visible-light absorption, and active sites. Moreover, Ti-Bi2WO6@ACB effectively inhibited the recombination of photogenerated carriers. The removal efficiency of Ti-Bi2WO6@ACB for 50 mg⋅L−1 CAP was 92.44 % at 120 min of irradiation, and the TOC removal rate was 67.72 %, which was significantly higher than that of the control treatment. Ti-Bi2WO6@ACB is reusable and photostable, with approximately 99 % sterilization of Staphylococcus aureus and Escherichia coli within 10 min of light irradiation and 48 h of cultivation. The addition of H2O2, ultrasonication, heating, and blowing air in the system improved the photocatalytic efficiency. The ultrasound enhancement mechanisms are related to the effects of cavitation, microjets, and photocatalysis coupled with sonocatalysis. CAP degradation was dominated by OH, O2−, and h+. The doping of Ti3+/TiO2 generated more defects and O2−, and the ACB acted as a carrier to prevent the agglomeration of TiO2 and Bi2WO6. Further, the degradation process of CAP was documented and the degradation pathways may include hydroxylation addition, methanol denaturation, substitution, C–N bond breaking, oxidation, hydrolysis, and decarboxylation reactions. The research presents fresh insights into the development of high-performance engineered biochar-based composite for environmental detoxification.

Synthesis and characterization of enhanced visible light-driven C-doped ZnO-2D GO/g-C3N4 heterojunction photocatalyst

Well-designed 2D graphene oxide-modified polymeric graphitic carbon nitride composite nanosheets (GO/g-C3N4) as desirable sensitizers and catalytic substrates for optimising the visible light-driven photocatalytic performance of ZnO-based photocatalysts have been investigated. Herein, 2D GO/g-C3N4 composite nanosheets are first developed by ultrasonic and hydrothermal methods, and then coupled with ZnO nanoparticles to prepare a series of ternary GO/g-C3N4-ZnO heterojunction composites with vary GO loading concentrations. Characterization of the photocatalysts was carried out by SEM, TEM, XPS, XRD, DRS, photoluminescence (PL) spectroscopy; evaluation of the visible light photocatalytic activity was performed by degrading an aqueous methylene blue (MB) solution. XPS studies showed that the formation of a ZnC bond in 15 % GO/g-C3N4-ZnO is due to the replacement of oxygen by carbon, indicating the construction of a hybrid heterojunction composed of C-doped ZnO and visible light sensitive GO/g-C3N4 composite nanosheets. The photodegradation performance of 15 % GO/g-C3N4-ZnO is 5.3, 2.9, and 2.2 times higher than that of pure ZnO, g-C3N4, and g-C3N4-ZnO, respectively. Due to the increase of GO loading in GO/g-C3N4 composite nanosheets, some characteristics of efficient visible light photocatalysis, such as a wider light absorption range, fluorescence quenching in the PL spectrum, excellent optical response in photocurrent measurement, and good stability，were confirmed and can be attributed to the electronic interaction between heterostructures and the effective transfer of photogenerated electrons in these ternary nanocomposites. This work may provide a new promising pathway for the construction of easily prepared 2D GO/g-C3N4 hybrid-modified nanocomposites, which is a hopeful material for wastewater control.

Porous cyclopentadiene unit-incorporated graphitic carbon nitride nanosheets for efficient photocatalytic oxidation of recalcitrant organic micropollutants in wastewater

For the purpose of searching for efficient photocatalysts to deal with recalcitrant organic micropollutants in wastewater, here an in-situ supramolecule self-assembly-thermal polymerization strategy is developed to prepare a series of porous cyclopentadiene (CPD) unit-incorporated g-C3N4 ultrathin nanosheets (CCPD-g-C3N4). The CCPD-g-C3N4 demonstrate CPD unit doping level-dependent and remarkably enhanced visible-light photocatalytic oxidation efficiency towards two organic micropollutants, acetaminophen and methylparaben, in which the optimized CCPD-g-C3N4-2 shows 6.1 and 3.5 times higher acetaminophen and methylparaben degradation rate than bulk g-C3N4; moreover, CCPD-g-C3N4-2 is still robust and efficient in the treatment of five mixed organic micropollutants in pharmaceutical wastewater, and the satisfactory micropollutant removal efficiency is obtained in a wide pH window and the presence of high concentrations of inorganic anions and cations as well as dissolved organic matters. Theoretical calculation combined with experimental test reveal that CCPD-g-C3N4 can significantly reduce ecological risk of the target pollutant after the photocatalytic degradation reaction. Such enhanced photocatalytic oxidation efficiency is dominated by the accelerated charge carrier separation dynamics and extended visible-light response region due to the incorporation of CPD units, which finally lead to the generation of abundant reactive oxygen species to degrade and mineralize target micropollutants efficiently.

Large enhancement of visible light photocatalytic efficiency of ZnO films doped in-situ by copper during atomic layer deposition growth

In the present study, we investigate the photocatalytic activity of ZnO thin films doped by copper atoms in successive steps during the film growth by the atomic layer deposition method. Scanning electron microscopy and x-ray diffraction measurements reveal a polycrystalline structure of samples with degrading crystallinity for films with higher Cu content. X-ray photoelectron spectroscopy analysis is consistent with the presence of copper in the Cu+ state for samples with a relative Cu content lower than 1 at.%. Those samples exhibit p-type conductivity indicating that copper ions occupy substitutional, CuZn, acceptor sites in ZnO. As established from UV–vis measurements, Cu-doped ZnO films also show enhanced optical absorption in the visible region. A reduced electron-hole recombination rate, due to much lower intrinsic free charge carrier concentrations in the doped samples, and the increased light absorption in the visible region, lead to a large enhancement of photocatalytic efficiency observed in doped films under simulated sunlight irradiation.

Synthesis and photocatalytic performance of composite g-C3N4 with functionalized multi-walled carbon nanotubes

A novel g-C3N4 composite photocatalyst was synthesized by one-step calcination using melamine and different functionalized multi-walled carbon nanotubes (MWCNT) as raw materials. The effect of additives on the photocatalytic performance of the composite g-C3N4 has been investigated. The results showed that the incorporation of functionalized MWCNT led to a porous structure in g-C3N4, increasing the specific surface area and availability of active sites. The addition of hydroxylated/carboxylated MWCNT (HMWCNT/CMWCNT) affected the band structure of g-C3N4 and reduced the band gap. The visible-light photocatalytic degradation efficiency of Rhodamine B (RhB) using g-C3N4 composited with various types and amounts of MWCNT was evaluated. Among them, g-C3N4 with 1 wt% CMWCNT showed the highest photocatalytic degradation efficiency of RhB and still had 92.71% photocatalytic activity after 5 cycles of degradation.