Separation Of Photoinduced Charge Carriers Research Articles

Promoting CdS photocatalytic activity through a coating layer of solid electrolyte LiTi2(PO4)3

Two major challenges in photocatalysis are the separation and utilization of photogenerated charge carriers that have limited their wider applications. To address these issues, significant studies have been devoted to the surface modification of photocatalysts. Herein, CdS nanorods were surface-modified by an ion-conducting LiTi2(PO4)3 (LTP) shell. This modification could accelerate the rapid separation and efficient utilization of photoinduced charge carriers. Therefore, CdS@LTP composite photocatalyst displayed a photocatalytic H2 evolution rate of 26.01 mmol g−1h−1 without any addition of cocatalysts in a Na2S/Na2SO3 solution, which was over 6-fold compared to CdS, and showed improved stability. Furthermore, this shell can prevent the reverse reactions between H2 and O2 during photocatalytic water splitting. With the photo-deposition of Pt cocatalysts, CdS@LTP-Pt can achieve efficient overall water splitting with the highest H2 generation rate (351 μmol g−1h−1), which is 3.25 times higher than that of CdS-Pt. This study broadens the application of ionic conductor materials and provides a new way for the design of advanced photocatalysts for solar energy conversion.

Implementation of visible light-driven photocatalytic degradation of antibiotic chloramphenicol using Bi2S3/ZrO2 and Bi2WO6/ZrO2 heteronanostructures

Zirconium dioxide-incorporated bismuth sulfide (Bi2S3/ZrO2) and bismuth tungstate (Bi2WO6/ZrO2) heteronanostructures (HNSs) were fabricated to serve as photocatalysts for the visible light-driven degradation of antibiotic chloramphenicol (CAP). A two-step hydrothermal process was applied to synthesize HNSs, and their structural and optical properties were validated by several analytical techniques. Interestingly, a multi-structural feature was ascertained in which nanoflower-structured ZrO2 was attached to the surface of nanorod- and nanosheet-structured Bi2S3 and Bi2WO6, respectively, resulting in the formation of Bi2S3/ZrO2 and Bi2WO6/ZrO2 HNSs. For the photocatalytic degradation of CAP, both HNSs showed magnificent catalytic activity during a visible light-based photocatalytic degradation. Furthermore, when peroxymonosulfate (PMS) was used as an activator for an oxidative catalytic reaction, the photocatalytic degradation rate was drastically enhanced to nearly 5 times. Bi2S3/ZrO2 and Bi2WO6/ZrO2 showed ∼96 % CAP degradation in 15 min, with rate constants of 0.2511 and 0.2163 min−1, respectively. The synergistic effects of the substantial generation and separation of photoinduced charge carriers are responsible for the highly improved catalytic activity. Scavenger analysis demonstrated that hydroxyl radical species predominated in the effective degradation process. These kinds of inorganic-based HNSs are expected to rule the field of contaminated water remediation, which will also expand a platform for the fabrication of photocatalyst materials.

Lattice Distortion in a Confined Structured ZnS/ZnO Heterojunction for Efficient Photocatalytic CO2 Reduction.

It is a promising strategy to effectively promote "carbon neutrality" by reducing CO2 to small energy molecules through photocatalysis technology. However, due to low light utilization and recombination of photogenerated carriers, photocatalysts usually have low activity and low selectivity for products. Herein, a hollow spherical ZnS/ZnO heterojunction with a spatial confinement effect photocatalyst was synthesized toward CO2 photoreduction through preciously controlling the nano-/microstructure. The local lattice distortions were introduced into the surface of the hollow ZnS/ZnO microsphere, which activated lattice oxygen and provided additional active reaction sites. Furthermore, the heterojunction constructed between ZnS and ZnO interfaces facilitated the separation of photoinduced charge carriers. Combined with the natural advantage of enhanced light capture and absorption for a hollow confined structure, as a result, the systemic design in the electronic and confined structures for the photocatalyst has brought an excellent CO2 reduction performance with a CO yield rate as high as 35.85 μmol g-1h-1 and durability under a 300 W Xe lamp irradiation without any sacrificial agent and cocatalyst.

Crystallization Engineering of CuNi2 S4 Ultra-Fine Nanocrystals with Optimized Band Structures for Efficient Photocatalytic Pollutant Degradation and Hydrogen Production.

The mono-dispersed cubic siegenite CuNi2 S4 ultra-fine (≈5nm) nanocrystals are fabricated through crystallization engineering under hot injection. The strong hydroxylation on mostly exposed CuNi2 S4 (220) surface leads to the formation of multi-valence (Cu+ , Cu2+ , Ni2+ , Ni3+ ) species with unsaturated hybridization and coordination micro-environments, which can induce rich redox reactions to optimize interfacial kinetics for the adsorbed reaction intermediates. The as-synthesized CuNi2 S4 nanocrystals with ultra-small particle size and the characteristics of being highly dispersed can increase specific surface area and hydroxylated active sites, which considerably contribute to the improvement of photocatalytic activities. Experimental and theoretical studies indicate that the CuNi2 S4 with unique surface condition can properly modulate the charge density distribution and the electronic band structure, thus achieving an optimal band gap for enhancing visible light absorption. Additionally, the strong hydroxylation on CuNi2 S4 (220) surface can not only make the photocatalytic process stable in alkaline environment but also bring about an impurity level between conduction and valence band, which facilitates the separation of photo-induced charge carriers by suppressing the rapid re-combination of exited electrons and holes. The optimization of band structure should be the intrinsic reason for the efficient photocatalytic pollutant degradation and hydrogen production under visible light illumination.

Controllable Crystal Growth and Improved Photocatalytic Activity of Porous Bi2O3-Bi2S3 Composite Sheets.

Porous Bi2O3-Bi2S3 composite sheets were constructed through a combinational methodology of chemical bath deposition and hydrothermal reaction. The Na2S precursor concentration in the hydrothermal solution was varied to understand the correlation between the vulcanization degree and structure evolution of the porous Bi2O3-Bi2S3 composite sheets. The control of the etching rate of the Bi2O3 sheet template and the regrowth rate of Bi2S3 crystallites via suitable sulfide precursor concentration during the hydrothermal reaction utilizes the formation of porous Bi2O3-Bi2S3 sheets. Due to the presence of Bi2S3 crystallites and porous structure in the Bi2O3-Bi2S3 composites, the improved visible-light absorption ability and separation efficiency of photogenerated charge carriers are achieved. Furthermore, the as-synthesized Bi2O3-Bi2S3 composite sheets obtained from vulcanization with a 0.01M Na2S precursor display highly enhanced photocatalytic degradation toward methyl orange (MO) dyes compared with the pristine Bi2O3 and Bi2S3. The porous Bi2O3-Bi2S3 sheet system shows high surface active sites, fast transfer, high-efficiency separation of photoinduced charge carriers, and enhanced redox capacity concerning their constituent counterparts. This study affords a promising approach to constructing Bi2O3-based Z-scheme composites with a suitable microstructure and Bi2O3/Bi2S3 phase ratio for photoactive device applications.

Construction of P-C3N4/C3N5 isotypic heterojunction for effective degradation of organic pollutants

BackgroundPhotocatalysis was an effective method for organic pollutant degradation, and graphitic carbon nitride g-C3N4 and g-C3N5 were famous two-dimensional semiconductors. Compared to the allotypic heterojunction, the band alignment and compatibility of isotypic heterojunction were superior. MethodsIn this work, an organic isotypic heterojunction was constructed via coupling phosphorus-doped C3N4 (P-C3N4) and g-C3N5. The characteristics were evaluated using transmission electron microscope, Fourier transform infrared, X-ray diffractometer, X-ray photoelectron spectrum, ultraviolet-visible (UV–vis) diffuse reflection spectrum, electronic spin resonance (ESR) analysis, photoluminescence spectrometer, electrochemical impedance spectroscopy, and photocurrent analysis. SignificantIsotypic heterojunction displayed high UV–vis light harvest, high separation efficiency of photo-induced charge carriers, and low surface resistance. Additionally, an internal-electric-field was established at the interface, which was beneficial for spatial separation of photo-induced charge carriers. As expected, the Rhodamine B (RhB) degradation efficiency was 7.3 and 12.3 times higher than that of the P-C3N4 and g-C3N5. Radical trapping experiment and ESR analysis indicated that •O2−, •OH, hole, 1O2, and electron played joint role in RhB degradation. In this work, a photocatalyst with excellent photocatalytic degradation properties was designed, and it provided a simple and novel strategy for environmental remediation.

Novel visible-light-active P-g-CN-based α-Bi2O3/WO3 ternary photocatalysts with a dual Z-scheme heterostructure for the efficient decomposition of refractory ultraviolet filters and environmental hormones: Benzophenones

The ubiquitous and refractory benzophenone (BP)-type ultraviolet filters, which are also endocrine disruptors, were commonly detected in the aquatic matrix and could not be efficiently removed by conventional wastewater treatment processes, thus causing extensive concern. Herein, a novel ternary nanocomposite, P-g-CN/α-Bi2O3/WO3 (P-gBW), was successfully fabricated by mixing cocalcinated components and applied to the decomposition of BP-type ultraviolet filters. The dual-Z-scheme heterostructure of P-gBW enhances visible-light absorption, efficiently facilitates separation and mobility, and prolongs the lifetime of photoinduced charge carriers via double charge transfer mechanisms. The optimum 95 wt% P-gBW exhibited excellent photocatalytic activity, degrading 96% 4-hydroxy benzophenone (4HBP) within 150 min and 93% 2,2′,4,4′-tetrahydroxybenzophenone (BP-2) within 100 min under visible-light illumination, respectively. The pseudo-first-order rate constant of 4HBP (1.15 h−1) was 6.8-, 3.1-, 3.3- and 2.2-fold higher than those of WO3, P-g-CN, α-Bi2O3, and P-g-CN/α-Bi2O3, respectively, while that of BP-2 (1.71 h−1) was 5.2-, 2.2-, 3.2- and 1.5-fold higher, respectively. The improved photocatalytic degradation was attributed to efficient photoinduced charge carrier separation and migration and prevented the recombination of electron holes, as verified by photoluminescence, transient photocurrent response, and electrochemical impedance spectroscopy. Trapping experiments, electron paramagnetic resonance, and band energy position indicated an efficient dual-Z-scheme heterostructure.

Enhanced artificial nitrogen fixation efficiency induced by construction of ternary TiO2/MIL-88A(Fe)/g-C3N4 Z-scheme heterojunction

Herein, a ternary TiO2/MIL-88A(Fe)/g-C3N4 heterojunction is successfully constructed through a facile hydrothermal strategy for enhancing solar energy harvesting and efficiency of catalytic nitrogen reduction induced by enlarged light absorption range, increasing interfacial charge transfer ability and desirable stability. Under the simulated sunlight irradiation, the N2 fixation experiment shows that the yield of NH3 reaches 1084.31 μmol/(g·h) over the TiO2/MIL-88A(Fe)/g-C3N4 photocatalyst, and the yield is significantly enhanced, which is 33.68 and 13.94 times that is higher than the pure TiO2 and g-C3N4, respectively. In a mean time, the excellent performance of the photocatalytic N2 fixation over the ternary TiO2/MIL-88A(Fe)/g-C3N4 is verified based on density function theory calculation and the decisive step over the composite is investigated by calculating Gibbs free energies of nitrogen reduction paths. The performance enhancement mechanism of TiO2/MIL-88A(Fe)/g-C3N4 is speculated, which indicates that the hybridized three-component system presents a desirable Z-scheme band alignment, resulting in the improvement of separation and transfer efficiency of photoinduced charge carriers. The article shows a new and high-efficiency TiO2/MIL-88A(Fe)/g-C3N4 photocatalysis for excellent nitrogen reduction ability.

Construction of S-scheme Zn0.2Cd0.8S/biochar aerogel architectures for boosting photocatalytic hydrogen production under sunlight irradiation

Developing highly efficient, stable, and full-spectrum responsive non-precious photocatalyst is high desirable due to photocatalytic water splitting is a green technology for hydrogen evolution. In this work, a type of biochar-based composite photocatalysts is fabricated by a facile green microwave-assisted aqueous chemical deposition, which consists of monodispersed Zn0.2Cd0.8S nanoparticles (ZCS NPs) uniformly decorating on three-dimensional (3D) biochar aerogel (BA) derived from the biomass castoff tangerine peel. As-engineered ZCS/BA composite photocatalysts exhibit significantly strengthened photocatalytic activities under solar irradiation, in which the optimal 0.4ZCS/BA sample (0.4 represents the molar of ZCS) achieves the average photocatalytic hydrogen production efficiency of 10.52 mmol g−1∙h−1, being 24.5 folds higher than that of monolithic ZCS alloy. The boosted photocatalytic hydrogen evolution is ascribed to the synergistic effect on the heteroarchitecture with the closely interfacial interaction, which is beneficial for increasing the broad-spectrum sunlight absorption, promoting the photo-induced charge carriers separation efficiency, and accelerating the chemical reaction dynamic rate by the photothermal effect. The step-scheme (S-scheme) electron transfer mechanism for binary ZCS/BA heterojunction is proposed based on the experimental data and density functional theory (DFT) calculation. The study guides a practical approach to developing biochar-based composites for highly efficient utilization of agricultural biomass resources as well as conversion of solar energy to fuel in photocatalysis.

In Situ Growth Facilitating the Piezo-Photocatalytic Effect of Zn1-xCdxS/ZnO Nanorods for Highly Efficient H2 Production.

Photocatalytic H2 production holds promise for alleviating energy and environmental issues. The separation of photoinduced charge carriers plays vital roles in enhancing the activity of photocatalytic H2 production. The piezoelectric effect has been proposed to be effective in facilitating the separation of charge carriers. However, the piezoelectric effect is usually restricted by the noncompact contact between the polarized materials and semiconductors. In this study, Zn1-xCdxS/ZnO nanorod arrays on stainless steel for piezo-photocatalytic H2 production are fabricated by an in situ growth method, achieving an electronic-level contact between Zn1-xCdxS and ZnO. The separation and migration of photogenerated charge carriers in Zn1-xCdxS are significantly improved by the piezoelectric effect induced by ZnO under mechanical vibration. Consequently, under solar and ultrasonic irradiation, the H2 production rate of Zn1-xCdxS/ZnO nanorod arrays achieves 20.96 μmol h-1 cm-2, which is 4 times higher than that under solar irradiation. Such a performance can be attributed to the synergies of the piezoelectric field of bent ZnO nanorods and the built-in electric field of the Zn1-xCdxS/ZnO heterostructure, which efficiently separate the photoinduced charge carriers. This study provides a new strategy to couple polarized materials and semiconductors for highly efficient piezo-photocatalytic H2 production.

Construction of S-scheme CdS/g-C3N4 heterojunctions with enhanced photocatalytic H2 evolution and Cr(VI) reduction performance

Construction of heterojunctions is one of the most attractive approaches to synthesize highly active photocatalysts. In this work, we prepared CdS/g-C3N4 (CSCN) heterojunctions with different molar ratio of CdS/g-C3N4 via ball milling for photocatalytic hydrogen production and removal of Cr(VI). The successful construction of CSCN heterojunctions was proved by the various characterization methods. Formation of CSCN heterojunctions not only generates more vacancies to act as active site, but also accelerates the separation of photoinduced charge carriers, endowing with more electrons to participate in the photocatalytic reduction reaction. 2%CSCN sample was confirmed to hold the highest separation and transfer performance of photoinduced e−/h+ pairs by photoelectric tests. 2%CSCN samples exhibit the highest photocatalytic H2 evolution rate (680.04 μmol/g/h), which is 3.63-fold higher than that of the bare g-C3N4 (146.83 μmol/g/h). The activity of photocatalyst was further examined by removal of Cr(VI) experiment. The results show that the reduction efficiency of Cr(VI) on 2%CSCN is 2.46-fold of that of on the single g-C3N4, and the elimination rate of Cr(VI) on 2%CSCN can reach 64% after 1 h under simulated sunlight illumination. The improved photocatalytic performance can be ascribed to the creation of appropriate C vacancies and the widened light absorption range induced by CdS. A rational mechanism for enhanced photocatalytic activity was proposed to further understand the separation and transfer of photogenerated carriers produced by heterojunctions.

Ag decorated ZnO for enhanced photocatalytic H2 generation and pollutant degradation

In this study, Ag/ZnO photocatalyst is synthesized in ethylene glycol (EG) medium using a one-pot hydrothermal method, where EG serves as both a reaction medium for the synthesis and a reduction medium for silver. Standard analytical techniques such as XRD, XPS, SEM-EDX, TEM, HR-TEM FTIR, BET, and UV–Vis spectroscopy are used to characterize the synthesized samples. The XRD and HR-TEM results show that Ag has been decorated on the ZnO photocatalyst. The results show that spherical Ag/ZnO has the highest photocatalytic activity for H2 evolution (30.1 μmol h−1) and RhB degradation. The increased photocatalytic activity can be attributed to the formation of the Schottky barrier at the heterojunction interface of metal-semiconductor and the plasmonic resonance effect of silver, which results in efficient separation and transportation of photo-induced charge carriers. This research could open up new avenues for the development of advanced ZnO-based visible light photocatalytic materials to address energy and environmental challenges.

Modulating the bridging units of carbon nitride for highly efficient charge separation and visible-light-responsive photocatalytic H2 evolution

Carbon nitrides have attracted broad attention in the field of photocatalytic H2 evolution. However, the design and preparation of carbon nitrides with highly efficient charge separation and transfer are still challenging. Here, we synthesized a novel heptazine derivative-based photocatalyst, named as M+U-x to overcome the inherent limitations of carbon nitrides (C3N4 and C3N5). Experimental and theoretical calculation results reveal that the resultant M+U-x is composed by electron-withdrawing C3N4 and electron-donating C3N5 moieties, which are integrated into the conjugated framework via N-atoms and azo bridging units to form molecular heterojunctions. Among these, M+U-3 can dramatically facilitate the spatial separation of photoinduced charge carriers, delivering significantly high visible-light-responsive H2 evolution activity of 372 μmol h−1 with an AQY of 21.6% at 400 nm. This work provides a novel strategy for rationally modulating the bridging units of carbon nitrides to acquire enhanced charge-carrier mobility and efficient photocatalytic H2 evolution from the molecular level.

Facile Fabrication of Highly Active CeO2@ZnO Nanoheterojunction Photocatalysts.

Photocatalyst performance is often limited by the poor separation and rapid recombination of photoinduced charge carriers. A nanoheterojunction structure can facilitate the separation of charge carrier, increase their lifetime, and induce photocatalytic activity. In this study, CeO2@ZnO nanocomposites were produced by pyrolyzing Ce@Zn metal-organic frameworks prepared from cerium and zinc nitrate precursors. The effects of the Zn:Ce ratio on the microstructure, morphology, and optical properties of the nanocomposites were studied. In addition, the photocatalytic activity of the nanocomposites under light irradiation was assessed using rhodamine B as a model pollutant, and a mechanism for photodegradation was proposed. With the increase in the Zn:Ce ratio, the particle size decreased, and surface area increased. Furthermore, transmission electron microscopy and X-ray photoelectron spectroscopy analyses revealed the formation of a heterojunction interface, which enhanced photocarrier separation. The prepared photocatalysts show a higher photocatalytic activity than CeO2@ZnO nanocomposites previously reported in the literature. The proposed synthetic method is simple and may produce highly active photocatalysts for environmental remediation.

CoPx co-catalyst decorated CdS hollow nanocubes as efficient photocatalysts for hydrogen production under visible light irradiation

Hollow structures have attracted attention because of high specific surface area, advantages of light scattering, and shortening the charge transfer distance. In this study, hollow CdS nanocubes (H-CdS) were successfully synthesized by PBA self-template method, and CoPx nanoparticles were decorated on H-CdS surfaces. The unique topography and the introduction of CoPx not only greatly improve the light utilization, but also make the photogenerated carriers to be efficiently separated. It can be found that the 1.0 wt% CoPx/H-CdS sample presents highest hydrogen production rate of 1710.4 μmol·g−1·h−1 with apparent quantum yield of 9.1% under irradiation of 420 nm monochromatic light. The characterization results further explored the kinetics of the photoinduced charge carrier transfer and separation pathways, density functional theory (DFT) calculations showed that CoPx could effectively inhibit the photogenerated carrier recombination and reduce the activation energy of H2 generation. This work provides a new perspective for designing high performance photocatalysts.

Atom-Precise Heteroatom Core-Tailoring of Nanoclusters for Enhanced Solar Hydrogen Generation.

While core-shell nanomaterials are highly desirable for realizing enhanced optical and catalytic properties, their synthesis with atomic-level control is challenging. Here, the synthesis and crystal structure of [Au12 Ag32 (SePh)30 ]4- , the first example of selenolated Au-Ag core-shell nanoclusters, comprising a gold icosahedron core trapped in a silver dodecahedron, which is protected by an Ag12 (SePh)30 shell, is presented. The gold core strongly modifies the overall electronic structure and induces synergistic effects, resulting in high enhancements in the stability and near-infrared-II photoluminescence. The Au12 Ag32 and its homometal analog Ag44 , show strong interactions with oxygen vacancies of TiO2 , facilitating the interfacial charge transfer for photocatalysis. Indeed, the Au12 Ag32 /TiO2 exhibits remarkable solar H2 production (6810µmolg-1 h-1 ), which is ≈6.2 and ≈37.8 times higher than that of Ag44 /TiO2 and TiO2 , respectively. Good stability and recyclability with minimal catalytic activity loss are additional features of Au12 Ag32 /TiO2 . The experimental and computational results reveal that the Au12 Ag32 acts as an efficient cocatalyst by possessing a favorable electronic structure that aligns well with the TiO2 bands for the enhanced separation of photoinduced charge carriers due to the relatively negatively charged Au12 core. These atomistic insights will motivate uncovering of the structure-catalytic activity relationships of other nanoclusters.

Highly Sensitive Chemiresistive H2S Detection at Subzero Temperature over the Sb-Doped SnO2@g-C3N4 Heterojunctions under UV Illumination.

NASA has detected H2S in the persistently shadowed region of the lunar South Pole through NIR and UV/vis spectroscopy remotely, but in situ detection is generally considered to be more accurate and convincing. However, subzero temperatures in space drastically reduce chemisorbed oxygen ions for gas sensing reactions, making gas sensing at subzero temperature something that has rarely been attempted. Herein, we report an in situ semiconductor H2S gas sensor assisted by UV illumination at subzero temperature. We constructed a g-C3N4 network to wrap the porous Sb doped SnO2 microspheres to form type II heterojunctions, which facilitate the separation and transport of photoinduced charge carriers under UV irradiation. This UV-driven technique affords the gas sensor a fast response time of 14 s and a response value of 20.1 toward 2 ppm H2S at -20 °C, realizing the sensitive response of the semiconductor gas sensor at subzero temperature for the first time. Both the experimental observations and theoretical calculation results provide evidence that UV irradiation and the formation of type II heterojunctions together promote the performance at subzero temperature. This work fills the gap of semiconductor gas sensors working at subzero temperature and suggests a feasible method for deep space gas detection.

In situ synthesis of g-C3N4/TiO2 heterojunction by a concentrated absorption process for efficient photocatalytic degradation of tetracycline hydrochloride.

The construction of heterojunctions between semiconductors is a preferred route to improve overall photocatalytic activity. In this work, a facile and feasible method was innovatively developed to one-step prepare g-C3N4/TiO2 heterojunctions via an absorption-calcination process using nitrogen and titanium precursors directly. This method can effectively avoid interfacial defects and establish a tight interfacial connection between g-C3N4 and TiO2. The resultant g-C3N4/TiO2 composites exhibited prominent photodegradation efficiency for tetracycline hydrochloride (TC-HCl) under visible light and simulated-sunlight irradiation. The optimal g-C3N4/TiO2 composite (urea content of 4g) showed the highest photocatalytic efficiency, which can degrade 90.1% TC-HCl under simulated-sunlight irradiation within 30min, achieving 3.9 and 2 times increases compared to pure g-C3N4 and TiO2, respectively. Besides, photodegradation pathways based on the role of active species ·O2- and ·OH were identified, indicating that a direct Z-scheme heterojunction was formed over the g-C3N4/TiO2 photocatalyst. The enhanced photocatalytic performance can be attributed to the close-knit interface contact and the formation of Z-scheme heterojunction between g-C3N4 and TiO2, which can accelerate the photo-induced charge carrier separation, broaden the spectra absorption range, and retain a higher redox potential. This one-step synthesis method may provide a new strategy for the construction of Z-scheme heterojunction photocatalysts consisting of g-C3N4 and TiO2 for environmental remediation and solar energy utilization.

An overview on InVO4-based photocatalysts: Electronic properties, synthesis, enhancement strategies, and photocatalytic applications

InVO4-based photocatalysts have attracted extensive interest in the realms of sustainable energy conversion and environmental applications, due to the narrow electronic band gap, high stability, nontoxicity, and high optical absorption. However, InVO4 has some limitations in that it can harvest less solar energy due the slow migration and separation of photoinduced charge carriers, which hinders its potential applications. Consequently, numerous attempts have been made to increase the photocatalytic activity of InVO4. In recent years, significant advances have been achieved in developing efficient photocatalysts. In this review, we provide an overview of the structure and electronic properties of InVO4 along with a brief discussion on the controlled synthesis routes of InVO4 as photocatalysts. Following that, a description of the modification strategies including heterojunction formation and doping is given. The mechanism of various InVO4-based photocatalysts along with their photodegradation efficiency for organic pollutants is discussed in this review. Thereafter, we summarize the potential applications of the photocatalytic InVO4 in the energy and environmental field. Lastly, the future perspective and knowledge gap in the direction of InVO4-based photocatalysts are also discussed.

Single-Step Synthesis of Graphitic Carbon Nitride Nanomaterials by Directly Calcining the Mixture of Urea and Thiourea: Application for Rhodamine B (RhB) Dye Degradation

Recently, polymeric graphitic carbon nitride (g-C3N4) has been explored as a potential catalytic material for the removal of organic pollutants in wastewater. In this work, graphitic carbon nitride (g-C3N4) photocatalysts were synthesized using mixtures of low-cost, environment-friendly urea and thiourea as precursors by varying calcination temperatures ranging from 500 to 650 °C for 3 h in an air medium. Different analytical methods were used to characterize prepared g-C3N4 samples. The effects of different calcination temperatures on the structural, morphological, optical, and physiochemical properties of g-C3N4 photocatalysts were investigated. The results showed that rhodamine B (RhB) dye removal efficiency of g-C3N4 prepared at a calcination temperature of 600 °C exhibited 94.83% within 180 min visible LED light irradiation. Photocatalytic activity of g-C3N4 was enhanced by calcination at higher temperatures, possibly by increasing crystallinity that ameliorated the separation of photoinduced charge carriers. Thus, controlling the type of precursors and calcination temperatures has a great impact on the photocatalytic performance of g-C3N4 towards the photodegradation of RhB dye. This investigation provides useful information about the synthesis of novel polymeric g-C3N4 photocatalysts using a mixture of two different environmentally benign precursors at high calcination temperatures for the photodegradation of organic pollutants.