High-efficiency Photocatalytic System Research Articles

Construction of TiO2@Cu2O-CuS heterostructures integrating RGO for enhanced full-spectrum photocatalytic degradation of organic pollutants

This study presents the development and optimization of TiO2@Cu2O-CuS heterostructures, enhanced with reduced graphene oxide (RGO), for efficient photocatalytic degradation of organic pollutants, focusing on imidacloprid. Two configurations, TiO2/RGO/Cu2O-CuS and Cu2O-CuS/RGO/TiO2, are explored to highlight the impact of material layering on photocatalytic efficiency. The strategic integration of RGO optimizes charge transfer, crucial for photocatalysis. Comprehensive characterization techniques, such as X-ray diffraction (XRD), Transmission Electron Microscopy (TEM), X-ray Photoelectron Spectroscopy (XPS), Raman spectroscopy, and Nitrogen adsorption-desorption isotherms, provide insights into the crystalline structure, morphology, surface chemistry, and textural properties of the heterostructures. The TiO2/RGO/Cu2O-CuS configuration significantly outperforms its counterpart in photocatalytic activity under full-spectrum (UV–VIS–IR) illumination, due to improved charge carrier dynamics and synergistic interactions between the composite materials. Remarkably, the TiO2/RGO/Cu2O-CuS assembly achieved over 95 % degradation of imidacloprid under simulated solar irradiation, marking a breakthrough in solar spectrum utilization for photocatalysis and exhibits promising recyclability, maintaining its high photocatalytic efficiency even after multiple degradation cycles, highlighting its potential for sustainable pollutant removal applications. Additionally, this configuration demonstrates a twofold increase in degradation efficiency compared to separate UV and VIS irradiations, emphasizing its rapid pollutant removal capability. This research underscores the critical role of material layer sequencing in developing high-efficiency photocatalytic systems and marks a significant advancement in environmental remediation technologies that harness renewable energy sources.

Conversion of Z-Scheme to type-II in dual-defective V2O5/C3N4 heterostructure for durable hydrogen evolution

The carbon nitride (C3N4) materials and hybrids have been acknowledged as promising photocatalysts for decades. The precise design and modulation of C3N4-based photocatalyst in defects and energy bands for further promotion is of importance but less investigated. In this work, a type of defective V2O5/C3N4 heterojunction with dual oxygen and carbon vacancy on interface is designed through simple annealing and plasma etching. The incorporation of V2O5 enables to promote the separation efficiency for photo-induced carriers and enhance built-in electric field (BIEF) at junction boundary to accelerate charge transport. The designed double defects in V2O5/C3N4 further results in a type-II heterojunction and switch of redox reaction sites, preventing photocatalytic corrosion of unstable V2O5. As a result, owing to the integrated advantages of such composite photocatalyst, the defective V2O5/C3N4 heterojunction exhibits a comparable hydrogen evolution rate of 0.90 mmol·g−1·h−1 to V2O5/C3N4, and dramatically improved regeneration with a continuous hydrogen evolution rate of 0.83 mmol·g−1·h−1 for 5 cycles. Our study is envisaged to provide a toolbox for rationally designing compositive nanomaterials toward high-efficiency photocatalytic systems.

Bio-inspired high-efficiency photosystem by synergistic effects of core-shell structured Au@CdS nanoparticles and their engineered location on {001} facets of SrTiO3 nanocrystals

Natural photosynthesis, which provides a green and high-efficiency energy conversion path by spatial separation of photogenerated carriers through combined actions of molecules ingeniously arranged in an efficient solar nanospace, highlights the importance of rational nanostructure design to realize artificial high-efficiency photosystem. Inspired by these unique features, we constructed a high-efficiency ternary photosystem by selectively decorating the {001} facets of 18-facet SrTiO 3 with Au@CdS photosensitizers via a green photo-assisted method. Benefiting from the dual-facilitated charge carriers transportation in core-shell structured Au@CdS heterojunction and well-faceted 18-facet SrTiO 3 nanocrystal, such a photocatalyst could realize the effective spatial separation of photogenerated electrons and holes. As expected, the 18-facet SrTiO 3 /Au@CdS photocatalyst exhibits superior activity in visible-light-driven photocatalytic hydrogen evolution (4.61 mmol h −1 g −1 ), 166% improvement in comparison with randomly deposited Au@CdS (1.73 mmol h −1 g −1 ). This work offers new insight into the development of green and high-efficiency photocatalytic systems based on the rational nanostructure design by crystal facet engineering.

Construction of a novel double S-scheme structure WO3/g-C3N4/BiOI: Enhanced photocatalytic performance for antibacterial activity

In recent years, the threat to human health from bacteria in wastewater has attracted attention, and photocatalytic technology has emerged as a promising strategy for inactivating bacteria in water. Therefore, it is of great research value to develop a novel high-efficiency photocatalytic system with the visible light response. We successfully designed a double S-scheme heterojunction composite WO3/g-C3N4/BiOI (WCB) in this paper. The preparation of WCB composites was demonstrated by a series of characterizations, including X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR) and transmission electron microscopy (TEM). The antibacterial effects of photocatalysts against representative Gram-negative strain Escherichia coli (E. coli) and Gram-positive strain Staphylococcus aureus (S. aureus) were tested under LED light irradiation. The novel photocatalyst presented excellent antibacterial properties, inactivating E. coli in 12 min and S. aureus in 20 min. The bacterial cell inactivation process was studied by scanning electron microscopy (SEM) and Confocal Laser Scanning Microscopy (CLSM). Active species capture experiments show that the active species present in the WCB composites in the process of inactivating bacteria are h+, e−, OH and O2−. In conclusion, the synthesized double S-scheme WCB photocatalyst exhibits remarkable photocatalytic antibacterial activity under LED light and has broad prospects for practical application in water antibacterial treatment.

Facile assembly and enhanced visible-light-driven photocatalytic activity of S-scheme BiOBr/g-C3N4 heterojunction for degrading xanthate in wastewater

The S-scheme BiOBr/g-C3N4 heterostructure composites with varying mass ratios were synthesized via a simple hydrothermal route. Compared to bare BiOBr and g-C3N4, the BiOBr/g-C3N4-10% photocatalyst performed the significantly enhanced photodegradation activity for ethyl xanthate in mineral flotation wastewater under visible light and possessed superior reusability as demonstrated by the reuse test. The degradation efficiency of BiOBr/g-C3N4-10% composite towards ethyl xanthate was up to 96.1% in 120 min, and its reaction rate constant was equal to about 6.3 times and 24.6 times that of bare BiOBr and g-C3N4, respectively. The improved visible-light-driven photodegradation activity was mainly attributed to the construction of S-scheme BiOBr/g-C3N4 heterojunction resulting in the effective separation of carriers. The results showed that superoxide radical (•O2–) played a dominant role in the degradation reaction. Furthermore, the carrier transfer mode in the S-scheme heterojunction and possible xanthate degradation mechanism was proposed. This paper provides a new idea for preparing S-scheme heterojunction and the construction of a high-efficiency photocatalytic system.

G-C3N4/CoTiO3 S-scheme heterojunction for enhanced visible light hydrogen production through photocatalytic pure water splitting

Photocatalytic hydrogen (H2) production via water splitting in the absence of sacrificial agents is a promising strategy for producing clean and sustainable hydrogen energy from solar energy. However, the realization of a photocatalytic pure water splitting system with desirable efficiency is still a huge challenge. Herein, visible light photocatalytic H2 production from pure water splitting was successfully achieved using a g-C3N4/CoTiO3 S-scheme heterojunction photocatalyst in the absence of sacrificial agents. An optimum hydrogen evolution rate of 118 μmol·h−1·g−1 was reached with the addition of 1.5 wt% CoTiO3. The remarkably promoted hydrogen evolution rate was attributed to the intensified light absorption coupled with the synergistic effect of visible light responsive CoTiO3, the promoted efficiency in charge separation, and the reserved strong redox capacity induced by the S-scheme charge transfer mechanism. This work provides an alternative to visible light-responding oxidation photocatalysts for the construction of S-scheme heterojunctions and high-efficiency photocatalytic systems for pure water splitting.

Defective ultra-thin two-dimensional g-C3N4 photocatalyst for enhanced photocatalytic H2 evolution activity

The two-dimensional semiconductor photocatalytic material has excellent photocatalytic H2 evolution activity. In order to further improve the hydrogen production activity of g-C3N4, this study improved the preparation process of g-C3N4 and obtained a new photocatalyst (name H-CN) with a higher absorption range, larger specific surface area, and faster hydrogen production activity. Compared with the originally prepared g-C3N4, the H-CN absorption range has been improved, and the utilization of visible light has reached 650 nm. When the doping amount of Pt cocatalyst was 1.0 wt%, the H-CN demonstrates excellent photocatalytic hydrogen production activity, with a hydrogen production rate of 4.3 mmol h−1·g−1, which was 7.0 times higher than that pure 1.0 wt% Pt/g-C3N4. The fluorescence spectroscopy of H-CN showed better separation of carriers and longer lifetime. This study has guiding significance for the preparation of subsequent ultra-thin nanosheet photocatalysts and the establishment of high-efficiency photocatalytic systems.

Degradation behaviors of naproxen by a hybrid TiO2 photocatalyst system with process components

A hybrid system combining microwave and a microwave discharge electrodeless lamp (MDEL) was proposed to overcome the limitations of conventional TiO2 photocatalysts. The degradation efficiency and mechanism of naproxen were determined using a series of single processes, including conventional TiO2 photocatalyst reactors and a hybrid system that fuses them. Although the degradation efficiency tended to increase after changing the experimental condition of a single process, the optimal conditions existed for these experimental conditions. On the other hand, remarkable synergy was observed in the fused process, whose efficiency was significantly higher than that of the unit process. In particular, the optimal degradation ability was obtained by adding hydrogen peroxide together with microwave irradiation. The seven intermediates in the proposed photocatalytic degradation pathway were generated by the demethylation and hydroxylation by hydroxyl radicals. These results are expected to provide new data on the design of high efficiency photocatalytic systems at low cost.

Merging Single-Atom-Dispersed Iron and Graphitic Carbon Nitride to a Joint Electronic System for High-Efficiency Photocatalytic Hydrogen Evolution.

Scalable and sustainable solar hydrogen production via photocatalytic water splitting requires extremely active and stable light-harvesting semiconductors to fulfill the stringent requirements of suitable energy band position and rapid interfacial charge transfer process. Motivated by this point, increasing attention has been given to the development of photocatalysts comprising intimately interfaced photoabsorbers and cocatalysts. Herein, a simple one-step approach is reported to fabricate a high-efficiency photocatalytic system, in which single-site dispersed iron atoms are rationally integrated on the intrinsic structure of the porous crimped graphitic carbon nitride (g-C3 N4 ) polymer. A detailed analysis of the formation process shows that a stable complex is generated by spontaneously coordinating dicyandiamidine nitrate with iron ions in isopropanol, thus leading to a relatively complicated polycondensation reaction upon thermal treatment. The correlation of experimental and computational results confirms that optimized electronic structures of Fe@g-C3 N4 with an appropriate d-band position and negatively shifting Fermi level can be achieved, which effectively gains the reducibility of electrons and creates more active sites for the photocatalytic reactions. As a result, the Fe@g-C3 N4 exhibits a highlighted intramolecular synergistic effect, performing greatly enhanced solar-photon-driven activities, including excellent photocatalytic hydrogen evolution rate (3390 µmol h-1 g-1 , λ > 420 nm) and a reliable apparent quantum efficiency value of 6.89% at 420 nm.

Construction of Recycling Photocatalytic Gels for the Disinfection of Pathogens and Degradation of Organic Pollutants.

Bismuth oxybromide (BiOBr) nanosheets are exciting photocatalysts for microbial disinfection and organic dye degradation. However, it remains a great challenge to easily recycle these nanomaterials and improve their photocatalytic ability. Herein, we constructed a novel photocatalytic BiOBr@PAG gel containing BiOBr nanosheets and polyacrylamide gel (PAG), based on peroxydisulfate‐induced polymerization reaction. The photocatalytic gel had equally distribution of BiOBr nanosheets on the surface, and could be easily recycled from water. More strikingly, the gel could also rapidly kill all tested pathogenic bacteria (i. e., Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus) under irradiation. Its disinfection activity is attributed to remarkable intracellular ROS production and oxidative cell damage. Furthermore, the gel had higher photocatalytic activity than BiOBr nanosheets alone during degradation of organic dyes. This study developed a novel strategy for preparation of easy‐recycling and high‐efficiency photocatalytic systems for practical application in environmental treatment and medicinal disinfection.

Metal-Organic Framework Photosensitized TiO2 Co-catalyst: A Facile Strategy to Achieve a High Efficiency Photocatalytic System.

A 3D metal-organic framework (ADA-Cd=[Cd2 L2 (DMF)2 ]⋅3 H2 O where H2 L is (2E,2'E)-3,3'-(anthracene-9,10-diyl)diacrylic acid) constructed from diacrylate substituted anthracene, sharing structural characteristics with some frequently employed anthraquinone-type dye sensitizers, was introduced as an effective sensitizer for anatase TiO2 to achieve enhanced visible light photocatalytic performance. A facile mechanical mixing procedure was adopted to prepare the co-catalyst denoted as ADA-Cd/TiO2 , which showed enhanced photodegradation ability, as well as sustainability, towards several dyes under visible light irradiation. Mechanistic studies revealed that ADA-Cd acted as the antenna to harvest visible light energy, generating excited electrons, which were injected to the conduction band (CB) of TiO2 , facilitating the separation efficiency of charge carriers. As suggested by the results of control experiments, combined with the corresponding redox potential of possible oxidative species, . O2- , generated from the oxygen of ambient air at the CB of TiO2 was believed to play a dominant role over . OH and h+ . UV/Vis and photoluminescence technologies were adopted to monitor the generation of . O2- and . OH, respectively. This work presents a facile strategy to achieve a visible light photocatalyst with enhanced catalytic activity and sustainability; the simplicity, efficiency, and stability of this strategy may provide a promising way to achieve environmental remediation.

The fundamental role and mechanism of reduced graphene oxide in rGO/Pt-TiO2 nanocomposite for high-performance photocatalytic water splitting

Recently, developing high-efficiency photocatalytic hydrogen generation photocatalysts and clarifying the inherent mechanism behind the enhancement of hydrogen generation activity have been the research focus. Here, we present a step-wise strategy to prepare Pt/TiO2/reduced graphene oxide photocatalysts and the inherent mechanism of the enhanced photocatalytic activities were systematically investigated. Experimentally, the 2wt% rGO doped rGO/Pt-TiO2 nanocomposites showed the superior solar-driven hydrogen generation rate (1075.68μmolh−1g−1), which was 81 times and 5 times higher than bare TiO2 and Pt/TiO2 samples, respectively. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectra (FT-IR) demonstrated the formation of TiOC bonds in the hybrid, which drove the shifting upwards of the valence band edge from +2.2eV to +1.83eV. Furthermore, photoelectrochemical tests indicated the electron density of PTG-2 was about one order of magnitude higher than TiO2. Moreover, DFT calculations displayed that the bandgap had been successfully narrowed from 2.88eV to 2.76eV and the original blank energy region located at TiO2 bandgap was filled with C2p orbitals, which resulted in excited electrons in TiO2 efficiently transferring to graphene. Consequently, the DFT calculations are in good agreement with the experimental results and physical characterizations. This study affords us a rational design of a high efficiency photocatalytic system for solar energy conversion.

Well incorporation of carbon nanodots with silicon nanowire arrays featuring excellent photocatalytic performances.

Recently, silicon (Si) nanowires have been intensively applied for a wide range of optoelectronic applications. Nevertheless, rare explorations considering the photodegradation of organic pollutants based on Si nanowires were performed, and they still require vast improvement, in particular for their degradation efficiency. In this study, broad-band and high efficiency photocatalytic systems were demonstrated through the good incorporation of Si nanowires with highly fluorescent carbon nanodots. The photodegradation rate of these intriguing heterostructure arrays under a 580 nm light illumination is approximately 6 times higher than that of sole Si nanowires, and more than 3.6 and 4.5 times higher than that of Si nanowire incorporated with silver and gold nanoparticles, respectively. Optimizing the luminescent behaviors of carbon nanodots leads to the involvement of multiple light sources that activate the photoexcitation of carriers within the Si nanowires. This feature was further elucidated by examining the corresponding photocurrents under light illumination, which presents currents 1.9 times higher than those with the sole Si nanowires. In combination with excellent wettability with dye solutions, the present heterostructured nanowire arrays have promised the robust photocatalytic capability with retained efficiency after cycling uses, which may open up unique opportunities for future pollutant detoxification and wastewater treatment.