Visible Light Response Range Research Articles

A novel lanthanum-modified polytitanium chloride coagulant: Efficient algae removal and enhanced photocatalytic ability of recycled algal sludge

The removal of harmful cyanobacterial blooms (HCBs) and reuse of the resulting algal sludge are pressing issues in current environmental governance and ecological conservation. Aiming at tackling the above-mentioned challenges, titanium (Ti)-based coagulants are promising candidates. However, most of them suffer from poor stability and weak actual algal removal ability, and recycling of the algal sludge usually produces titanium dioxide (TiO2) with low photocatalytic ability. In this work, a lanthanum (La)-modified polytitanium chloride (La-PTC) coagulant is reported. La in the La-PTC coagulant serves a "kill two birds with one stone" strategy in algae removal and algae sludge reuse. Owing to the introduction of La ions, the La-PTC coagulant exhibits ultra-high stability and excellent algae removal capability with an efficiency of 98.71%, which is 7.25% higher than that of PTC coagulant. Moreover, recycling algae sludge can prepare high catalytic (2.45 times the commercial P25 TiO2) La/C-TiO2, where the presence of La enhances its visible light response range and inhibits electron hole recombination. The strategy of this La modified coagulant can not only achieve efficient removal of HCBs, but also transform the recovered algal sludge into photocatalysts with higher catalytic capacity.

Iron mediated n → π* electron transitions and mid-gap states formation in CN under low-temperature secondary calcination enhances photodegradation of organic pollutants

Iron modified carbon nitride (CN) materials have attracted widespread attention from researchers in different application fields. In this paper, single atom iron anchored CN (FeCN) with mid-gap states and n → π* electron transition was synthesized through low temperature secondary calcination. The mid-gap states introduce surface states capable of trapping photogenerated electrons, enabling FeCN to absorb photons with energies lower than its intrinsic optical bandgap. 10%FeCN also exhibits distinct optical absorption above 490 nm derived from the n → π* electron transition, which expand the visible light response range of photocatalysts and enhance electron transport ability. Additionally, the Fe-Nx site enhances the separation and transmission efficiency of photoexcited charges. The prepared 10%FeCN exhibits extremely high photocatalysis and photo-Fenton activity. Mercaptobenzothiazole (MBT) degradation rate of 10%FeCN is 3.47 times higher than CN, achieving a mineralization rate of 86.7% in 100 min. Additionally, the oxytetracycline hydrochloride (OTC) degradation rate of 10%FeCN in photo-Fenton reaction is 11.9 times higher than CN. After five cycles, this catalyst still has good reactivity, indicating its good stability.

Interface engineering of AgI/(P, K)-g-C3N4 novel S-scheme heterostructures as a highly efficient photocatalyst for RhB degradation

In this study, we developed an in-situ deposition method to load small-sized AgI nanoparticles as an oxidative photocatalyst (OP) onto phosphorus (P) and potassium (K) co-doped two-dimensional porous g-C3N4 (PK-CN-N) as a reductive photocatalyst (RP), forming an S-scheme heterojunction photocatalyst AgI/PK-CN-N. PK-CN-N achieved morphology control and element doping, leading to surface functionalization and heterostructure formation for the AgI/PK-CN-N photocatalyst. Notably, the 50AgI/PK-CN-N composite demonstrated an approximately 95 % removal efficiency for RhB within 30 minutes, 17.6 times higher than pure g-C3N4, surpassing most reported g-C3N4-based photocatalysts. The enhanced photocatalytic efficiency is attributed to the surface modification strategy and heterostructure formation of g-C3N4, which broadens the visible light response range, increases the number of active sites, improves the separation of photogenerated electron-hole pairs, and enhances REDOX capabilities. The band structure of the composite was elucidated through Mott-Schottky analysis and UV–vis DRS. The formation of the AgI/PK-CN-N S-scheme heterojunction and its charge transfer mechanism was confirmed through XPS, band structure analysis, KPFM, and EPR spectroscopy. Experimental data confirmed the presence of a strong and effective interface electric field between the two semiconductors, leading to band bending and accelerated charge separation. Additionally, the introduction of small-sized AgI semiconductors enhanced the exposure of the coupling interface, further improving catalytic performance. The reusability and lifespan of the catalyst were also analyzed, showing that after four cycles, the photocatalytic activity remained above 92 %.

Construction of a 2D/2D Vs-ZnIn2S4/Zn-TCPP heterojunction for effective charge transfer to enhance photocatalytic hydrogen evolution

The integration of inorganic and organic semiconductor components in composites has tremendous potential in photocatalysis, owing to the ultrafast photogenerated exciton dissociation and slow carrier recombination kinetics at their interfaces, which can result in enhanced photocatalytic performances. By exploiting the synergy among morphology modulation, sulfur vacancy (Vs) engineering, and close interface control, a novel inorganic–organic Vs-ZnIn2S4/ tetrakis (4-carboxyphenyl) zinc porphyrin (Zn-TCPP) composite for photocatalytic hydrogen evolution (PHE) was successfully synthesized via microwave-assisted solvothermal and self-assembly methods. The cocatalyst-free PHE rate of Vs-ZnIn2S4/Zn-TCPP (ZZT-20 %) reaches 8.997 mmol h−1 g−1 under visible light irradiation, which is 10.9, 2.2, and 67.1 times that of ZnIn2S4, Vs-ZnIn2S4, and Zn-TCPP, respectively. Moreover, the apparent quantum yield of ZZT-20 % under 420 nm monochromatic light (1.11 %) clearly exceeds that of Vs-ZnIn2S4. Testing experiments and DFT calculations revealed that the significantly enhanced PHE activity can be mainly attributed to the Z-scheme charge transfer mechanism, which greatly improves the visible light response range and redox potentials. Remarkably, Vs sites act as electron traps, inducing the vertical transport of electrons within the bulk phase and their accumulation at the surface Zn–S bonds. Simultaneously, van der Waals forces and weak hydrogen bonds between Vs-ZnIn2S4 and the Zn-TCPP interface cause the rapid migration of photogenerated electrons to Zn-TCPP. This work not only reveals new insights into the structure–property relationships of inorganic–organic Vs-ZnIn2S4 and Zn-TCPP composites, but also provides an appropriate strategy for cleaner water resourcelization and sustainable solar energy conversion.

Synthesis of lignin-based covalent organic frameworks bio-composites: Quantitative evaluation of adsorption-photoreduction of hexavalent chromium

A novel bio-covalent organic framework (COF: TpPa-SO3H/Lignin) based on TpPa-SO3H and lignin from lignocellulose was synthesized for chromium (Cr(VI)) remediation in this study. Results showed that TpPa-SO3H/Lignin had a highest adsorption capacity at the range of 5 ∼ 75 mg/L Cr(VI) under 10 mg/L dosage, in which 100 % Cr(VI) could be removal within 120 min. Likewise, the introduction of lignin improved the visible light response range, charge separation and photogenerated carriers, thereby improving the photocatalytic efficiency of Cr(VI) by TpPa-SO3H/Lignin. The highest photocatalytic efficiency of TpPa-SO3H/Lignin (98.56 %) was observed at the acidic conditions. ESR result shows that e- and ·O2– are generated and played an important role during the photocatalytic reaction, while the contribution of ·OH to Cr(VI) photoreduction is negligible. This study presents a sustainable and efficient approach to mitigating Cr(VI) pollution. It opens up avenues for further exploration of lignocellulose-derived materials in environmental applications and highlights the potential of COFs in addressing heavy metal contaminants.

Research Progress in Preparation and Modification Strategies of Graphitic Carbon Nitride for Efficient Photocatalysis: A Mini Review

With the acceleration of industrialization, energy shortage and environmental pollution are becoming more and more serious. It is urgent to develop green and sustainable new energy. Photocatalytic technology, especially the use of solar energy to convert chemical energy, has attracted much attention due to its environmental friendliness and sustainability. As an excellent photocatalyst, graphitic carbon nitride (g-C3 N4 ) has emerged rapidly in the field of photocatalysis due to its low cost, simple preparation and nontoxicity. However, g-C3 N4 has some limitations in practical applications, such as small specific surface area, weak photogenerated carrier transport capacity and narrow visible light response range. To overcome these challenges, researchers have modified g-C3 N4 through various strategies to improve its photocatalytic performance. In this paper, the synthesis methods and modification strategies of g-C3 N4 are summarized from the structural characteristics of g-C3 N4 , and its research focus and application prospect in the field of photocatalysis are prospected.

Synergistic vacancy defects and the surface hydrophobic-to-superhydrophilic wetting engineering in W/S co-doped BiOI for enhanced photocatalytic hydrogen evolution

Bismuth oxyhalide (BiOI) has been used for photoelectrochemical catalysis in the field of catalytic hydrogen evolution, but it in a single-phase form has hardly been reported for photocatalytic hydrogen evolution reaction (PHER). Herein, we designed a W/S co-doped BiOI-based superhydrophilic catalyst with oxygen vacancy-rich defects and heterovalent valence states for efficient PHER under visible light. The W/S doping in BiOI not only adjusts the energy band structure and expands the visible light response range, but also transforms its hydrophobicity into superhydrophilicity, with which the gas bubble amount can be reduced and PHER activity enhanced. The introduction of sulfur regulates the content of oxygen vacancies which enhance the active surface sites for capturing water molecules and activating the H-O-H bond. The added tungsten exists in different valence states of W6+ and W5+ which is beneficial for electron hopping and PHER activity. The W/S-BiOI-3 with the suitable W/S doping content exhibits the highest visible-light PHER rate of 9.46 mmol·g−1·h−1, with an apparent quantum efficiency (AQE) of 9.7 % at 420 nm. W/S-BiOI-3 shows excellent PHER activity, stability, and durability, which provides a feasible scheme for other bismuth-based halogen oxides to be used in PHER.

Reactive oxygen boosts photocatalytic oxytetracycline degradation and H2O2 production by K, O and cyano co-modified carbon nitride

Engineering photocatalysts to enhance the production of reactive oxygen species holds great importance in realizing effective water purification and hydrogen peroxide (H2O2) generation. Herein, the K, O, and cyano co-modified carbon nitride (KOCN) was constructed using thermal polymerization. Under visible light irradiation, KOCN showed excellent oxytetracycline hydrochloride (OTC) degradation efficiency and H2O2 generation rate. During the photocatalysis, rich reactive oxygens involving ·O2-, 1O2, H2O2, and ·OH were detected. Additionally, the production of H2O2 was attributed to a two-step single-electron oxygen reduction reaction (ORR). DFT and characterization analyses confirmed that the doping of K and O as well as the formation of cyano groups expanded the visible light response range, adjusted the band structure, and improved the separation of photogenerated carriers. This study presents a novel approach for developing efficient, stable, and reusable photocatalysts to address contemporary environmental challenges.

Visible-Light Photocatalytic Degradation Efficiency of Tetracycline and Rhodamine B Using a Double Z-Scheme Heterojunction Catalyst of UiO-66-NH2/BiOCl/Bi2S3.

BiOCl is a promising photocatalyst, but due to its weak visible light absorption capacity and low photogenerated electron-hole pair separation rate, its practical application is limited to a certain extent. In this study, a novel double Z-scheme heterojunction UiO-66-NH2/BiOCl/Bi2S3 catalyst was constructed to broaden the visible light response range and promote high photogenerated hole-electron separation of BiOCl. Its photocatalytic performance is evaluated by dissociating tetracycline (TC) and rhodamine B (RhB) in visible light. The optimal proportion of UiO-66-NH2/BiOCl/Bi2S3 hybrids exhibits the best degradation efficiency of visible light illumination (∼93% in 120 min for TC and ∼98% in 60 min for RhB). The synergistic effect of a large visible light response range and the Z-scheme charge transfer mechanism ensure the excellent visible photocatalytic activity of UiO-66-NH2/BiOCl/Bi2S3. It is proven that h+ and •O2- are the main active substances in the photocatalysis process by active substance capture experiments and electron spin resonance tests. The intermediates and degradation processes are analyzed by high-performance liquid chromatography-mass spectrometry. This study proves that the new UiO-66-NH2/BiOCl/Bi2S3 photocatalyst has great application potential in the field of water pollution degradation and will provide a new idea for the optimization of BiOCl.

Designed construction of boosted visible-light Z-scheme TiO2/PANI/Cu2O heterojunction with elaborated photocatalytic degradation of organic dyes

A novel TiO2/polyaniline/Cu2O (T/PANI/Cu) ternary nanocomposite was synthesized via a facile in-situ polymerization of aniline and a one-step solvothermal method. The ternary nanocomposite Ti/PANI/Cu with Z-scheme heterojunction exhibited excellent photocatalytic performance as well as improved stability. The photocatalytic performance of the prepared photocatalysts (T, T/PANI, and T/PANI/Cu) was investigated by the photocatalytic decomposition of Methyl Orange dye (MO) as an organic contaminant using visible light illumination. The T/PANI/Cu ternary nanocomposite revealed the highest degradation efficiency up to 99.5% after 25 min, which is much higher than that of T (47%) and T/PANI (73%). The development of Z-scheme heterojunction is credited with the increased activity and generation of an electric field that led to an improved structure, a wider visible light response range, and a lower rate of electron-hole pair recombination. Based on trapping tests, ·O2−·OH, and h+ species were the main active species involved in the photocatalytic degradation of MO dye. Even after the fifth cycle, the T/PANI/Cu composite remained effective in the successive photocatalytic decomposition of MO, maintaining over 90% of the original degradation efficiency.

Constructing S‐scheme heterojunctions with tunable interfacial oxygen vacancy via UiO‐66‐NH2‐derived ZrO2‐x for efficient photocatalytic performance

Defects engineering is significant for photocatalytic environment remediation. To this end, visible‐light‐driven α‐Fe2O3/ZrO2‐x S‐scheme heterojunction photocatalysts with optimal oxygen vacancy (Ov) defects are successfully synthesized via a two‐step method. Compared with pristine UiO‐66‐NH2‐derived ZrO2‐x and α‐Fe2O3, the heterojunction photocatalysts exhibit a wider range of visible light response and higher efficiency in separating photogenerated electron–hole pairs. Among them, the 5% α‐Fe2O3/ZrO2‐x sample shows the best photocatalytic performance to the degradation of tetracycline (TC) (89.3%), in which the pseudo‐first‐order kinetic rate constants are 8.20 and 16.75 times that of pristine ZrO2‐x and α‐Fe2O3, respectively. The outstanding photocatalytic degradation efficiency can be attributed to both the narrow‐bandgap ZrO2‐x with visible light response and the formation of α‐Fe2O3/ZrO2‐x S‐scheme heterojunctions. During the formation of heterojunctions, the concentration of oxygen vacancies (Ov) at the interface of α‐Fe2O3/ZrO2‐xdecreases monotonically with the increasing loading of α‐Fe2O3, thereby altering the electronic structure of the photocatalyst and forming the heterojunction firmly. In addition, the high stability implies the potential applications in fields of environment.

The construction of Z-scheme heterojunction ZnIn2S4@CuO with enhanced charge transfer capability and its mechanism study for the visible light degradation of tetracycline

In this study, copper oxide (CuO) was prepared by the microwave-assisted hydrothermal technique subsequently, CuO was grown in situ onto different rare metal compounds to prepare Z-scheme heterojunctions to improve the degradation efficiency of tetracycline (TC) in water environments. Various characterization proved the successful synthesis of all composite materials, and the formation of tight heterojunction interfaces, among which, the core–shell structure ZnIn2S4@CuO exhibited excellent photocatalytic degradation capability. Research results indicated that the degradation efficiency of ZnIn2S4@CuO for TC (50 mg/L) in the water environment reached 95.8 %, and the degradation rate is 2.41 times and 12.93 times that of CuO and ZnIn2S4 alone, respectively, the reason is because of the introduction of ZnIn2S4, Z-scheme heterojunction structures and internal electric field (IEF) is constructed and formed to extend the visible light response range of photocatalysts to improve electron-hole separation efficiency, and enhance charge transfer. In addition, ZnIn2S4@CuO-2 exhibited good stability and reproducibility, with no significant loss of activity after five cycles. Finally, the precise locations of free radical attack on TC were investigated by the combined use of high-resolution mass spectrometry (HR-MC) and frontier electron densities (FEDs), and a reasonable degradation pathway was provided. The results of this research provide a new and viable approach to overcome the limitations of conventional photocatalytic materials in terms of limited visible light absorption range and fast carrier recombination rates, which offers promising prospects for a wide range of applications in the field of wastewater purification.

The synergistic effect of POM-π interaction and solid phase amidation on the visible light photocatalytic of g–C3N4–based photocatalyst

Due to the unique ability of Keggin-type polyoxometalate (POM) to remain stable when accepting electrons to form mixed valence POM, organic-POM hybrid materials can complete multi-electron transfer while maintaining structural stability. The organic-POM hybrids photocatalysts prepared using organic materials and POM as raw materials have been developed to form new energy bands and crystal structures. This not only enhances their quantum efficiency and but also expands their visible light response range. Nevertheless, organic-POM hybrids, featuring organic amines as ligands, are prone to photoetching, impeding g-C3N4's progress in this area. In this paper, the amino group of g-C3N4 was converted into imide ring by solid phase amidation method, which overcame this obstacle and converted g-C3N4 into g-C3N4 based polyimide (CNPI) with enhanced photoelectric properties. XRD, IR spectrum, and XPS data indicate that CNPI is more tightly integrated with potassium phosphotungstate (KPW) than g-C3N4, demonstrating superior electron transport capabilities and potentiated POM-π interactions. In terms of photocatalytic efficacy, CNPI/KPW-30 % exhibits an impressive degradation rate constant of 0.5458 h−1 for imidacloprid, attributed to its compact microstructure and superior charge transfer capability. While maintaining good photocatalytic stability, the mineralization rate of CNPI/KPW-30 % to imidacloprid was 55.25 %. In addition, h+ and ·O2− were identified as active species through trapping agent experiments, and the degradation pathway was advanced by ESR technology analysis.

Three-dimensional donor-acceptor conjugated porous polymers based on metal-porphyrin and triazine for highly effective photodegradation of organic pollutants in water

Three-dimensional donor-acceptor (D-A) type conjugated porous polymers (CPPs) was designed and synthesized via imine condensation of copper tetraaminoporphyrin (CuTAPP) as donor and 1,3,5-tris-(4-formyl phenyl) triazine (TFPT) as acceptor, named as CuPT-CPP. The CuPT-CPP possesses a high specific surface area (73.7 m2/g) and excellent photophysical properties. The simultaneous introduction of the organometallic molecules and D-A structures in CuPT-CPP could be broadened the visible-light response range (400–800 nm) and facilitated efficient photogenerated carrier separation and transportation. As heterogeneous photocatalysts, CuPT-CPP has excellent photocatalytic performances under visible light irradiation, leading to excellent model pollutant rhodamine B degradation efficiency up to about 100% in 3 h, it has superb stability and reusability during the photocatalytic processes, and CuPT-CPP also exhibited broad substrate adaptability, which could photocatalytic degradation of methylene blue (MB), methyl orange (MO), and tetracycline hydrochloride (TC). This work indicates that three-dimensional D-A type porphyrin- and triazine-based CuPT-CPP has great potential in the practical application of photocatalysis.

Synthesis of novel Ag/AgBr/K0.4Y0.7Sb2O6.25 nanocomposite with enhanced photocatalytic properties

Devoloping efficient wastewater treatment photocatalysts capable of improving water quality is undoubtedly one of the main problems of present society. In recent years, novel plasmonic photocatalysts have shown new possible applications in photocatalytic wastewater treatment due to their unique properties. In this work, a novel Ag/AgBr/K0.4Y0.7Sb2O6.25 composite was successfully fabricated by photo-reduction using the pre-prepared AgBr/K0.4Y0.7Sb2O6.25 and K0.4Y0.7Sb2O6.25 (KYSbO). The AgBr/KYSbO and KYSbO were synthesized by deposition-precipitation and precipitation-heating methods. The visible-light photocatalytic performance of parent KYSbO and Ag/AgBr/KYSbO composite was evaluated using methylene blue (MB) as a model organic pollutant. The effects of catalyst dosage, pH and the initial concentration of the MB dye solution on the photocatalytic activity were also investigated in this study. Remarkably, the Ag/AgBr/KYSbO composite exhibited superior visible-light photocatalytic activity for the degradation of MB than that of parent KYSbO. MB was degraded to 91.6% in the presence of parent KYSbO after visible irradiation of 180 min, while 93.2% degraded in merely 30 min in the case of Ag/AgBr/KYSbO composite. The superior improvement in the photocatalytic activity of the Ag/AgBr/KYSbO composite can be credited to the efficient separation of photoinduced electron-hole pairs and the extended visible-light response range. Superoxide radicals are crucial for MB photocatalytic degradation in the Ag/AgBr/KYSbO composite. The possible photocatalytic mechanism was proposed.

Designing B–C3N4/Bi2WO6 to construct a Z-type hybrid heterostructure for efficient degradation of antibiotics

Constructing nanocomposite structures with good charge transfer pathways is an effective way to obtain high-efficiency photocatalysts. Therefore, we prepared a Z-scheme heterojunction B–C3N4/Bi2WO6 composite material by combining 2D B–C3N4 nanosheets and 2D Bi2WO6 nanosheets. The composite catalyst exhibited significant multi-purpose photocatalytic activity against the antibiotics. When the Bi2WO6 proportion was 100 % (The proportion of Bi2WO6 to B–C3N4 is 1:1), the degradation efficiency of TC-HCl reached 85.7 % within 90 min, demonstrating the best photocatalytic performance. UV–vis showed that the visible light response range of the photocatalytic material shifted to the infrared region, possibly due to the construction of a Z-type heterojunction. The PL results showed that the electron-hole recombination rate of B–C3N4 is lower than that of g-C3N4 due to B-doping. Doped heterostructures can effectively enhance the performance of photocatalytic materials and offer a novel approach to pollutant degradation.

Construct 2D/1D BiOX (X = Cl, Br)@Bi5O7I heterojunctions with rich interfaces and wide visible light response range for pollutant removal in water under LED light

At present, the development of photocatalysts with high visible light sensitivity and efficient catalytic activity for environmental pollution control is the focus of research in the field of photocatalysis. In this work, 2D/1D BiOX (X = Cl, Br)@Bi5O7I heterojunction with abundant interfaces was prepared by a low-temperature liquid-phase method using Bi5O7I nanorods as substrate and BiOX nanoflakes as shell. The rich interfaces can be used as transport bridge for photogenerated electrons between Bi5O7I and BiOX. Under the optimum condition of BiOX content of 60%, the surface charge transfer efficiency increased from 20.79% (Bi5O7I) to 55.44% (BOI-BC-60) and 67.36% (BOI-BC-60) according to the photoelectrochemical measurement results. In the application of photocatalytic degradation of levofloxacin, the prepared BiOX (X = Cl, Br)@Bi5O7I heterojunctions exhibited enhanced adsorption capacity in darkness and improved photocatalytic activity under visible light. The reaction rate and pollutant removal efficiency of BOI-BC-60 and BOI-BB-60 were 6.87, 2.07 and 12.17, 3.28 times higher than that of Bi5O7I, respectively. It is proved that the suitable valence band and conduction band positions of BiOX and Bi5O7I components in BiOX@Bi5O7I heterojunction provide thermodynamic conditions for the migration of photogenerated electrons and holes.

3DOM BiOI/TiO2 composites modified by metal Ag with broad spectrum response for photocatalytic degradation and water splitting

In order to improve the photocatalytic performance of TiO2 and expand its absorption range in the visible light region, depositing noble metals, constructing the p-n heterojunction and controlling the morphology were used to modify TiO2. First, the TiO2 photocatalyst with a three-dimensional ordered macroporous structure was prepared by vacuum impregnation combined with calcination, and then the 3DOM Ag/BiOI/TiO2 composites were successfully prepared by the in-situ deposition and photoreduction. The characterization results show that the composites present a large number of open and transparent pore structures. The pore wall is formed by stacking TiO2 nanoparticles, with BiOI and Ag nanoparticles evenly distributed on the surface of the pore wall and in the macroporous framework, which expands the specific surface area of 3DOM TiO2 and provides more active sites for the reaction. The introduction of BiOI and Ag expands the visible light response range and improves the light utilization efficiency. Furthermore, the formation of the Schottky barrier and the internal electric field formed by the p–n heterojunction effectively promotes the interfacial electron transfer and suppress the electron–hole recombination, thereby generating more active species during the photocatalytic process. The experimental results of multi-mode photocatalytic degradation of methyl orange (MO) also show that 3DOM Ag/BiOI/TiO2 photocatalyst has the best photocatalytic degradation activity. In addition, different samples were tested for hydrogen production by photolysis of water under simulated sunlight conditions, and the results show that 3DOM Ag/BiOI/TiO2 has the best hydrogen production ability of photolysis of water. The excellent performance of multi-modal photocatalytic degradation of organic pollution and high photohydrogen production activity in 3DOM Ag/BiOI/TiO2 composites is attributed to the synergistic effect between the introduction of metallic Ag, the unique 3DOM structure, and the p–n heterojunction.

Photocatalytic degradation performance of antibiotics by WO3/α-Fe2O3/zeolite type II heterojunction with core-shell structure.

The accumulation of antibiotics in the environment can be harmful to human health, and research on their disposal technologies is of increasing interest. In this study, WO3/α-Fe2O3/zeolite (WFZ) type II heterojunction composites with core-shell structures were prepared by coupling WO3 semiconductors with visible-light photocatalytic activity with α-Fe2O3 via hydrothermal synthesis using zeolite as a carrier for the adsorption of synergistic photocatalytic degradation of antibiotics in wastewater. X-ray diffraction, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), specific surface, and porosity measurements were used to characterize the structure of WFZ type II heterojunction. The performance of WFZ heterojunction for the visible photocatalytic degradation of antibiotics (tetracycline hydrochloride (TCH), ciprofloxacin (CIP), and levofloxacin hydrochloride (LVF)) was investigated. Through four photocatalytic cycles, the catalyst exhibited excellent durability and stability. This was attributed to the core-shell structure and type II heterojunction promoting the effective separation of photogenerated carriers and the extended visible light response range, which resulted in the best photocatalytic activity of the catalyst under visible light irradiation. Radical trapping experiments showed that superoxide radicals (•O2-) and hydroxyl radical (•OH) were the main active species that played a major role in the photocatalytic degradation. These findings show that the synthesized WFZ type-II heterojunction can be used as a reliable visible-light-responsive photocatalyst for the treatment of antibiotics in wastewater.

Efficient N-P type charge compensatory synergistic effect for hydrogen production from water splitting: Theoretical design of V/Nb-Re co-doping MoX(X=S or Se)2 photocatalyst

The photocatalytic hydrogen evolution reaction (HER) is a promising method for solving the current environmental and energy crisis. Photocatalysts based on two-dimensional (2D) transition metal dichalcogenides (TMDCs) have received extensive attention in this field, and methods such as doping have been developed to further improve their photocatalytic efficiency. However, the photocatalytic efficiency is limited by the fact that the photogenerated carriers in a single doping system can easily recombine at impurity levels. Designing crystal structures of 2D TMDCs that can efficiently split water for hydrogen evolution is an important problem to solve for photocatalytic efficiency. Herein, we design the crystal structures of MoX(X=S or Se)2 co-doped with V/Nb and Re atoms using the density functional theory (DFT). Through N-P type co-doping, we deduce that this charge compensation effect indeed eliminates the impurity levels introduced by single-atom doping, not only expanding the visible light response range but also matching the thermodynamic conditions of photocatalytic water splitting, exhibiting excellent HER performance. The successful design of a V/Nb-Re co-doped MoX(X=S or Se)2 crystal structure is a key step for the practical application of 2D TMDC-based photocatalysts.