Design Of Heterojunctions Research Articles

Constructing Co3O4/La2Ti2O7 p-n Heterojunction for the Enhancement of Photocatalytic Hydrogen Evolution.

Layered perovskite-type semiconductor La2Ti2O7 has attracted lots of attention in photocatalytic hydrogen evolution, due to the suitable energy band position for water splitting, high specific surface area, and excellent physicochemical stability. However, the narrow light absorption range and the low separation efficiency of photogenerated carriers limit its photocatalytic activity. Herein, plate-like La2Ti2O7 with uniform crystal morphology was synthesized in molten NaCl salt. A p-n heterojunction was then constructed through the in situ hydrothermal growth of p-type Co3O4 nanoparticles on the surface of n-type plate-like La2Ti2O7. The effects of Co3O4 loading on photocatalytic hydrogen evolution performance were investigated in detail. The results demonstrate that composite Co3O4/La2Ti2O7 possesses much better photocatalytic activity than the pure component. The composite photocatalyst with 1 wt% Co3O4 exhibits the highest hydrogen evolution rate of 79.73 μmol·g−1·h−1 and a good cycling stability. The photoelectrochemistry characterizations illustrate that the improvement of photocatalytic activity is mainly attributed to both the enhanced light absorption from the Co3O4 ornament and the rapid separation of photogenerated electron-hole pairs driven by the built-in electric field close to the p-n heterojunction. The results may provide further insights into the design of high-efficiency La2Ti2O7-based heterojunctions for photocatalytic hydrogen evolution.

Elaborate interface design of CoS2/Fe7S8/NG heterojunctions modified on a polypropylene separator for efficient lithium-sulfur batteries

Lithium-sulfur (Li-S) batteries are considered as the most promising energy storage system due to their high specific capacity and resource abundance. However, the low electronic conductivity of S8 and Li2S, shuttle effects of lithium polysulfides (LiPSs), and sluggish reaction kinetics hinder the advance of Li-S batteries. The key to addressing the issues mentioned above is to improve the electrical conductivity of the cathode, enhance the absorption of LiPSs and accelerate the conversion. Nevertheless, it is a great challenge to simultaneously optimize them all. In this study, by incorporating the virtues of the large lamellar structure and strong nonpolar adsorption of reducedgrapheneoxide (rGO), strong polar polysulfide adsorption of Fe7S8 and excellent catalytic polysulfide activity of CoS2, a CoS2/Fe7S8 heterostructure grown on the nitrogen-doped rGO (CoS2/Fe7S8/NG) was prepared. Besides, the experiments demonstrate that the designed CoS2/Fe7S8/NG possesses strong absorption and superior catalytic ability towards LiPSs. Subsequently, when applied as a modification layer for the polypropylene (PP) separator, the CoS2/Fe7S8/NG-PP coupled with CNT/S cathode exhibits a high initial discharge capacity (1459 mAh g−1 at 0.1 A g−1), a reversible capacity of 731 mAh g−1 after 100 cycles at 0.2 A g−1, and a robust cycling stability (0.058 % flowing rate at 1.0 A g−1). Moreover, the cathode with a high sulfur mass loading of ∼ 3.8 mg cm−2 can still display a reversible capacity of 663 mAh g−1 after 100 cycles at 0.2 A g−1. More importantly, the study shown herein shed light for the design of heterojunction to improve the electrochemical performance of Li-S batteries.

Enhanced charge transfer in TiO2 nanoparticles/ MoO3 nanostructures bilayer heterojunction electrode for efficient electrochromism

Electrochromic smart windows play a significant role in energy saving technologies and there is a need to find more efficient as well as cheaper electrode materials suitable for this application. Electrode materials with adequate usage of nanostructuring and novel design strategies can help in improving the charge transfer and achieving better electrochromic performance. Herein, we explored a nanostructured electrode with the bilayer heterojunction design employing environmental friendly & cost effective TiO2 and MoO3 in an electrochromic device. A bilayer electrode with nanoparticulate TiO2 in the bottom layer and randomly oriented MoO3 nanostructures as the top layer has been adopted for the first time. The electrode exemplified a superior performance in terms of high current density and charge storage capacity as well as rate capability as compared to the relevant reports in the literature. A color contrast of 38%, switching response of ~2 s and high coloration efficiency of 72.5 cm2/C were achieved. The device has also shown good cyclic stability and high reversibility. The enhanced performance is ascribed to the nanostructured morphology of the electrode and the built-in potential at the interface, which improved the charge transfer, electrical conductivity and ionic transport in the device. The study presents a new viable approach of electrode design with nanoparticle bottom layer to improve the electrochromic performance capabilities, which can be extended to any other electrochromic materials as well.

In situ synthesized α-Fe2O3/BCN heterojunction for promoting photocatalytic CO2 reduction performance

The conversion of CO2 into clean fuels by utilizing solar energy is still limited by a low photoconversion efficiency, and heterojunction photocatalysts are considered a very effective way to solve this problem. Herein, a heterojunction system consisting of hematite (α-Fe2O3) and boron carbonitride (BCN) was fabricated through a one-pot ionothermal method. α-Fe2O3 nanoparticles were grown in situ on the surface of BCN nanosheets, forming an α-Fe2O3/BCN heterojunction (FBCN) with tiny amounts of α-Fe2O3 (less than 2 wt%). The as-synthesized FBCN catalyst with 1.46 wt% α-Fe2O3 provides the highest CO2 photoreduction activity (55.1 µmol g−1 for CO) without any cocatalyst or sacrificial reagents, which is 3.9 times higher than that obtained for pure BCN. The enhanced CO2 reduction activity can be attributed to the high surface area and effective interface-contacted heterostructure, which endows the catalyst with broadband visible light absorption, suppressed separation of photogenerated electron holes, and promoted charge transfer. Meanwhile, cycling experiments demonstrate that the FBCN photocatalyst shows good reusability and stability. This work can assist in the design and preparation of BCN-based heterojunctions with effective CO2 reduction performance.

Embedding CsPbBr3 perovskite quantum dots into mesoporous TiO2 beads as an S-scheme heterojunction for CO2 photoreduction

Heterojunction engineering, especially S-scheme heterojunction, has been recognized as a promising way to explore photocatalysts with boosted charge separation and CO2 photoreduction. Herein, we develop a CsPbBr3@mesoporous TiO2 beads (MTB) S-scheme heterojunction by embedding CsPbBr3 perovskite quantum dots (QDs) into the pores of MTB. The intimate interfacial interaction and staggered band structures promised the S-scheme charge transfer route, as confirmed by X-ray photoelectron spectra (XPS), electron spin resonance (ESR), etc. The 0.15CsPbBr3@MTB (15 wt% of CsPbBr3) hybrid exhibited a remarkable yield of 145.28 μmol g−1h−1 for CO2 photoreduction under simulated sunlight irradiation, which was 4.64 and 3.49-fold enhancement than the pristine MTB and CsPbBr3, respectively. This study provides useful guide towards the design of perovskite-based heterojunctions for photocatalytic applications.

Synergistic photocatalysis of Z-scheme type Fe2O3/g-C3N4 heterojunction coupled with reduced graphene oxide

The rational design of a Z-scheme heterojunction that appropriately connects two semiconductors with different bandgap with matched energies is of great significance for the efficient separation of charge carries and maximum solar-light harvesting. Furthermore, achieving a morphologically controlled, an easily synthesized, and an effective solar-light-driven photocatalyst still presents a significant challenge. Firstly, one-step hydrothermal method was used to facilely synthesize C-Fe2O3@rGO by incorporating cubic shape hematite (C-Fe2O3) with reduced graphene oxide (rGO). Then, graphitic carbon nitride (g-C3N4) was combined with C-Fe2O3@rGO via a solvothermal reaction, which resulted in the ternary heterojunction of C-Fe2O3@rGO@g-C3N4. Under exposer of simulated solar light, the photocatalytic performance of the constructed materials was assessed towards the destruction of methyl orange (MO) organic contaminant. For comparison, C-Fe2O3 and C-Fe2O3@rGO exhibited a very low photocatalytic activity, with degradation efficiencies of MO dye as 1% and 8%, respectively. In contrast, C-Fe2O3@rGO@g-C3N4 (5.0 wt.% g-C3N4) demonstrated a significantly greater photocatalytic efficiency of ∼40%, due to the formation of a ternary heterojunction. This structure ensures enhanced separation of charge carriers and extended solar-light harvesting. Strikingly, in the existence of a hole scavenger, C-Fe2O3@rGO@g-C3N4 had a significantly increased photocatalytic efficiency of 93%. The rate constants were 1.6 × 10−4 and 1.1 × 10−3 min−1before and after adding the hole scavenger EDTA-2Na, respectively. This result clearly confirms the successful formation of a Z-scheme nature heterojunction composed of two semiconductors (Fe2O3 and g-C3N4) and conductive rGO. This synthetic approach can provide a guideline for the rational engineering as well as facile fabrications Z-scheme systems devoid of noble metals for advanced photocatalytic applications.

The rational design of a graphitic carbon nitride-based dual S-scheme heterojunction with energy storage ability as a day/night photocatalyst for formic acid dehydrogenation

Photocatalytic formic acid dehydrogenation (FAD) has been regarded as one of the most promising methods of producing H2 in a sustainable manner. In the photocatalytic FAD reaction, photogenerated holes play an important role in the reaction mechanism and thus in the efficiency of photocatalysts. However, the design of photocatalytic systems capable of generating high hole potential without compromising the reducing ability of the photocatalyst is extremely rare for the FAD reaction. In this respect, we report herein a novel and highly efficient heterojunction photocatalyst composed of 2D graphitic carbon nitride, 2D MnO2, 1D MnOOH, and 0D PdAg alloy nanoparticles, denoted as GCN/MnO2/MnOOH-PdAg, that can create high reduction and oxidation potentials via a dual S-scheme heterojunction. The photocatalysts exhibited a superb photocatalytic activity in the FAD with a record turnover frequency (TOF) of 3919 h−1 under visible light irradiation, which was 6-, 5.2- and 24-times greater than those of GCN-PdAg, GCN/MnO2-PdAg, and MnO2/MnOOH-PdAg heterojunctions, respectively. The structure and dual S-scheme mechanism of the photocatalyst have been clearly demonstrated by extensive instrumental analysis, radical trapping tests, and scavenger experiments. More importantly, it was discovered that the presented photocatalyst continued to function with comparable activity in dark for a prolonged time using the same photocatalytic mechanism. The activity of the photocatalyst in dark was attributed to the utilization of electrons stored on Mn2O3, which was detected as a 4–5 nm thick layer on the surface of MnOOH nanorods. This study, in addition to being the first example of both a “day/night photocatalyst” for FAD with an S-scheme mechanism, also demonstrates for the first time the boosting of FAD via a dual S-scheme heterojunction photocatalyst.

Highly efficient visible-light-driven photocatalytic degradation of gaseous toluene by rutile-anatase TiO2@MIL-101 composite with two heterojunctions

The construction of heterophase junctions by rutile-anatase TiO2 is considered an effective strategy for toluene degradation, but the photogenerated electron utilization is still insufficient. In this study, the formation of type-II heterojunction by the encapsulation of Materials of Institut Lavoisier (MIL-101) by anatase is performed, and then the heterophase junction is further constructed to improve the catalytic performance of the photocatalyst. The enhancement of photocatalytic performance depends on the encapsulation of MIL-101 by anatase, the light absorption capacity of anatase, and the contact area of two heterojunctions. Photogenerated electrons are transferred to oxygen vacancies of anatase and promoting the generation of oxygen-containing radicals. The material certifies the synergistic effect of the heterophase junction and heterojunction design and provides a theoretical basis for application in the degradation of volatile organic compounds.

Design of polymeric carbon nitride-based heterojunctions for photocatalytic water splitting: a review

Design of polymeric carbon nitride-based heterojunctions for photocatalytic water splitting: a review

Design of multifunctional near-infrared organic heterojunction and double hole transport layer to improve efficiency and stability of perovskite solar cells

• Single-walled carbon nanotubes acts as a double hole transport layer. • Multifunctional bulk organic heterojunction provides additional light harvesting. • Heterojunction and buffer layer enhance the stability of perovskite solar cells. Currently, the high-efficiency lead organic–inorganic hybrid perovskite solar cells (PSCs) can only utilize a relatively small fraction of sunlight (300–800 nm) due to the limited tunability of optical bandgap, which is the key factor limiting the further improvement of the photoelectric conversion efficiency (PCE) of PSCs. Here, we report a method to blend the narrow band gap non-fullerene acceptor molecule Y18 and the wide band gap donor molecule PM6 to form a multifunctional bulk organic heterojunction active layer. To avoid the loss of voltage and fill factor caused by the compromised hole transport layer (HTL), we introduce the single-walled carbon nanotubes as a buffer layer to fabricate a double HTL. The champion device displays a PCE improvement from 20.05% to 22.82% with a relative increase of 13.81%. After a deep examination of the mechanism, organic heterojunction provides the multifunctional roles as follows: (1) providing additional harvesting to the near-infrared light ranging of 800–950 nm; (2) passivating the perovskite surface and grain boundary to reduce the defect density; (3) promoting hole extraction from perovskite to HTLs by forming cascade energy levels. Moreover, the stability of PSCs is considerably enhanced because the introduction of organic heterojunction and buffer layer design isolated the natural degradation, which enhances the tolerance towards water and oxygen. Finally, a module group is fabricated by connecting two series modules in parallel, which is served as a power source to light the diode screen. This work demonstrates a buffer layer design for fabricating organic heterojunction-perovskite integrated solar cells to expand the near-infrared response, which provides a novel approach for designing integrated solar cells in the future.

Two-dimensional semiconductor heterojunction nanostructure for mutually synergistic sonodynamic and chemoreactive cancer nanotherapy

• Designing tumor microenvironment-responsive and sono-responsive two-dimensional heterojunction nanostructure. • Achieving chemoreactive and sonocatalytic cancer nanotherapy triggered by tumor microenvironment and ultrasound. • Superior performance of anti-tumor effect with high biosafety enabled by chemoreactive and sonocatalytic nanotherapy. Ultrasound (US)-activated sonodynamic therapy (SDT) has been extensively explored as an effective therapeutic modality for cancer treatment due to its noninvasiveness, physical targeting and deep tissue penetration. However, the inorganic semiconductor sonosensitizer-enabled SDT still suffers from the low therapeutic efficacy because of tumor hypoxia and low separation efficiency of electrons (e − ) and holes (h + ) from the energy-band structure of these inorganic sonosensitizers. Herein, the two-dimensional (2D) TiO 2 @MnO 2-x heterojunction nanostructure was rationally designed and engineered for simultaneously modulating the tumor hypoxic microenvironment and augmenting the therapeutic efficacy of SDT against tumor. The MnO 2-x component was heterogeneously grown onto the surface of initially synthesized 2D TiO 2 nanosheets (NSs), which not only acted as the catalysts for converting tumor-overexpressed hydrogen peroxide into oxygen and subsequently modulating the tumor hypoxia, but also catalyzed the Fenton reaction for the production of hydroxyl radicals. The heterojunction design of TiO 2 @MnO 2-x nanostructure effectively augmented the SDT efficacy of TiO 2 -based sonosensitizers under ultrasound activation by facilitating the separation of e − /h + pairs. The simultaneously endowed tumor-hypoxia alleviation and synergistic sono/chemodynamic tumor nanotherapy achieved the high tumor cell-killing effect and tumor-suppression efficiency, as systematically demonstrated both in vitro and in vivo . This work provides a distinct paradigm of the heterojunction semiconductor nanostructure design for improving the ultrasound-based nanotherapy and achieving high tumor-treatment efficacy.

Computation-guided design and preparation of durable and efficient WC-Mo2C heterojunction for hydrogen evolution reaction

Molybdenum and tungsten carbides (Mo 2 C and WC) are promising catalysts for hydrogen evolution reaction (HER), but their electrocatalytic activities are still inferior to theoretical predictions. Herein, density functional theory (DFT) calculations imply that WC-Mo 2 C heterostructure may exert a high HER performance since the hybridization of WC and Mo 2 C can optimize the proton adsorption energy and energy barrier for water dissociation. To test this predication, we prepare the WC-Mo 2 C heterostructure on a flexible carbon cloth (CC). The obtained WC-Mo 2 C@CC exhibits notable HER activity ( η10 = 122 mV; η500 = 309 mV) and stability (continuous 100 h at 500 mA cm −2 ) in alkaline media. Furthermore, a solar-panel-driven electrolyzer, including the WC-Mo 2 C@CC cathode and a NiFe-LDH@Ni f anode, operates at 10 mA cm −2 with a cell voltage of 1.51 V in 10 M KOH at 70°C, demonstrating its potential for practical applications. Overall, this work offers an atomic-level insight into designing advanced carbide HER electrocatalysts. • WC-Mo 2 C heterostructures are prepared by one-step co-deposition • WC-Mo 2 C show competitive alkaline catalytic HER performance • The optimized ΔG H∗ and super hydrophilic nature account for its good HER activity • A water electrolyzer driven by solar energy is operated at industrial conditions WC-Mo 2 C heterostructures are prepared by one-step co-deposition in KF-B 2 O 3 -Na 2 WO 4 -Na 2 MoO 4 molten salts by Liu et al. The WC-Mo 2 C heterostructures show a high HER performance owing to the optimized ΔG H∗ and low energy barrier for water spitting.

Dimensional heterojunction design: The rising star of 2D bismuth-based nanostructured photocatalysts for solar-to-chemical conversion

Dimensional heterojunction design: The rising star of 2D bismuth-based nanostructured photocatalysts for solar-to-chemical conversion

Compositional and morphological design of heterojunction modified by Schottky junction as highly efficient microwave absorbers

The ubiquitous and further deterioration of electromagnetic environment has put forward higher demand for microwave absorption materials with the rapid advancement of 5 G communication and artificial intelligence. Rational manipulation of materials with unique heterojunctions and adjustable electromagnetic properties as lightweight and high-efficiency microwave absorption is the focus and difficulty of research at home and abroad. Schottky junction is designed and fabricated via implanting Fe/MnO2 nanocrystal confined in carbon matrix, wherein core nanoclusters are tailored. Manganese oxide coupling magnetic metallic iron lamellar nanocrystal benefits the improvement of static magnetization and tuning graphitization degree. The fascinating heterojunction by modifying a Schottky junction can not only enable balance among loss capacity and impedance matching, but also can accelerate the carrier migration and promote abundant interfaces. The efficient microwave absorption is optimized yielding maximum reflection loss of − 53.60 dB and broadening the effective bandwidth of 6.35 GHz. Furthermore, tailoring the morphology of implanted core nanoclusters successfully realizes selective-frequency of microwave absorption. The ternary Fe/MnO2@C composite formed by the self-assembly of Fe/MnO2 nanocrystal core and carbon shell show superior advantages compared to binary composite (e.g., Fe@C, Fe@MnO2, MnO2@C) in microwave absorption performance. Thus, the performances of appropriately tailored nanoclusters with unique architecture endow optimal synergistic effects between magnetic and dielectric loss.

An efficient construction method of S-scheme Ag2CrO4/ZnFe2O4 nanofibers heterojunction toward enhanced photocatalytic and antibacterial activity

The combination of multiple optimization methods has become one of the hot strategies for the development of novel photocatalysts. Therefore, in this paper, the S-scheme Ag2CrO4/ZnFe2O4 (ACO/ZFO) nanofibers heterojunction photocatalyst is successfully prepared by co-precipitation method by loading ACO particles on the surface of ZFO nanofibers. It is found that ACO/ZFO composites not only have the advantages of higher specific surface area and more exposed active sites, but also the successful construction of S-scheme heterojunction effectively inhibits the recombination of photoelectron-hole pairs and generates more active groups, showing its superior redox ability. ACO/ZFO composites have excellent photocatalytic performance under the enhancement of multiple properties. The results showed that under the simulated visible light, the 40%ACO/ZFO composite with the best photocatalytic activity has the highest sterilization rate of 98.7%, which is 2.1 times and 3.3 times of ACO and ZFO, respectively, and the degradation rate of MB is 3.1 times and 4.7 times of ACO and ZFO, respectively. The mechanism of S-scheme ACO/ZFO nanofibers heterojunction photocatalyst was investigated by free radical experiment. This work provides new insights into the design and development of S-scheme heterojunctions for environmental remediation and sterilization.

A novel hierarchical nanostructured S-scheme RGO/Bi2MoO6/Bi2WO6 heterojunction: Excellent photocatalytic degradation activity for pollutants

The S-scheme heterogeneous photocatalysts have outstanding photocatalytic performance resulting from the suitable matching of band edge potential. In this study, a hierarchical hollow microsphere assembled by Bi2WO6 nanoplates and Bi2MoO6 nanoparticles were anchored on RGO to form a ternary S-scheme RGO-Bi2MoO6/Bi2WO6 (BMWG) heterojunction. Remarkably, the photocatalytic efficiency of BMWG the rhodamine B (RhB) degradation under visible light irradiation respectively exhibits 33, 4, and 2 times of enhancement compared to that of P25, Bi2WO6, and Bi2MoO6/Bi2WO6 with high photo-corrosion stability over 5 cycles. The improvement of photocatalytic activity and stability are mainly ascribed to the S-scheme heterojunction between Bi2MoO6 and Bi2WO6 and incorporation of graphene that further accelerates the separation and migration of the photogenerated charge carriers at the heterogeneous interfaces. This study provides an insight into the design and fabrication of S-scheme hierarchical nanostructured heterojunction of high photocatalytic activity.

Built-In Electric Field Directs Electron Transport at Ultrathin Ni(OH)2/Metal–Organic Framework Interface for Efficient Photocatalytic CO2 Reduction

Rational design of heterojunctions as photocatalysts that can help alleviate the energy and environmental crisis relies on the efficient electron transfer to the catalytically active sites. In this work, a robust metal–organic framework (MOF)-based heterostructured catalyst for the CO2 reduction reaction (CRR) was reported, taking advantage of a synergy effect between ultrathin (1.5 nm thickness) Ni-rich Ni(OH)2 nanosheets (NSs) and the highly stable and conductive Fe-rich Prussian blue (PB). This Ni(OH)2/PB photocatalyst can attain an optimal CO evolution rate of 108.8 mmol h–1 g–1 and a high CO selectivity (88.2–95.0%) in the CRR. The stable PB helps atomically thin Ni(OH)2 NSs to be well-dispersed and exposed in the heterojunction. A built-in electric field found at the interface of the bulk-sized PB and the ultrathin Ni(OH)2 further directs the electron transfer. Intriguingly, the conductive PB can quickly capture the electrons from the Ru-based photosensitizer and then rapidly sends them to the CRR-active Ni(OH)2 in the Z-scheme Ni(OH)2/PB system, accounting for its high efficiency and high selectivity over CO2 reduction into CO. The findings underline the versatility and the mechanistic response of MOFs in constructing advanced catalysts.

Switching charge transfer of g-C3N4/BiVO4 heterojunction from type II to Z-scheme via interfacial vacancy engineering for improved photocatalysis

Constructing type II heterojunction is an efficient strategy to enhance the light absorption and promote the charge transport. However, the improvement effect is limited by the decreased redox ability of charge carriers. The rational design of heterojunction from type II to Z-scheme is expected to overcome this obstacle. Herein, we demonstrate that the introduction of interfacial oxygen vacancies (OVs) can switch charge transfer of g-C3N4/BVO heterojunction from type II to Z-scheme. The interfacial OVs acted as the reactive center of charge carriers to quench the electrons of BVO and holes of g-C3N4, thereby promoting charge separation and migration. As a result, the interfacial OVs mediated Z-scheme g-C3N4/BVO heterojunction kept the strong oxidation/reduction potential of two single-component photocatalysts thereby significantly enhancing the photodegradation of tetracycline and CO2 photoreduction. The kinetic constant of tetracycline degradation on the optimal g-C3N4/BVO-20 sample was 2.04-fold and 2.29-fold higher than those on g-C3N4 nanosheets and pure BVO, respectively. This work provides a feasible strategy by the interfacial vacancy engineering of heterojunction for enhanced photocatalysis.

Novel organic/inorganic PDI-Urea/BiOBr S-scheme heterojunction for improved photocatalytic antibiotic degradation and H2O2 production

The matched energy band structure and efficient carrier separation efficiency are the keys to heterogeneous photocatalytic reactions. A novel organic/inorganic step scheme (S-scheme) heterojunction PDI-Urea/BiOBr composite photocatalyst was constructed by simple solvothermal reaction combined with in-situ growth strategy. The composite photocatalyst not only has high chemical stability, but also can generate and accumulate a large number of active species (h + , • O 2 − , • OH, H 2 O 2 ). PDI-Urea/BiOBr showed higher photocatalytic activity for the degradation of antibiotic such as ofloxacin (OFLO), tetracycline (TC) and the production of H 2 O 2 in the spectral range of 400-800 nm. The apparent rate constant of 15% PDI-Urea/BiOBr for photocatalytic degradation of TC (or OFLO) was 2.7 (or 2.5) times that of pure BiOBr and 1.7 (or 1.8) times that of pure PDI-Urea. The H 2 O 2 evolution rate of 15% PDI-Urea/BiOBr was 2.5 times that of PDI-Urea and 1.5 times that of BiOBr, respectively. This work has formed a mature S-scheme heterojunction design thought and method, which offers new visions for the development of heterogeneous photocatalysts. A novel organic/inorganic S-scheme heterojunction PDI-Urea/BiOBr composite photocatalyst showed higher photocatalytic activity for the degradation of tetracycline (TC), ofloxacin (OFLO) and the production of H 2 O 2 in the spectral range of 400-800 nm.

The design of heterojunctions based on boron-/phosphorus-doped graphene and ZnO monolayer to enhance adsorption properties for toxic gases

Boron-/phosphorus-doped graphene and ZnO monolayer (B-G/ZnO and P-G/ZnO) heterojunctions are modeled. The density functional theory is performed to investigate the optimal adsorption configurations, electronic and adsorption properties of oxycarbide (CO, CO2), oxynitride (NO, NO2), and sulfide (SO2, H2S) gas molecules adsorbed on the heterojunctions. Results indicate that the adsorption characteristics of both B-G/ZnO and P-G/ZnO heterojunctions are better than those of G/ZnO heterojunction. Specifically, NO2 and SO2 gas molecules are chemisorbed on doped heterojunctions, and the adsorption energies are almost three times more than that on the G/ZnO heterojunction. Then, the two gas molecules are simultaneously adsorbed on the two opposite terminals of the doped G/ZnO heterojunctions to evaluate the influence of gas concentration on electronic and adsorption properties of the G/ZnO heterojunction. It is found that the adsorption energy almost doubles compared with adsorbing a gas molecule, which provides a new idea to regulate the electronic and adsorption properties of the G/ZnO heterojunction. In addition, the bandgap of graphene can be opened by B and P atom doping and the p–n junction and n–n junction can be formed with the ZnO monolayer, respectively. The theoretical investigation helps us to better understand the mechanism of G/ZnO heterojunctions as gas sensors and offers the guidance for future p–n and n–n junction designs used in advanced gas sensor devices.