Spatial Separation Of Charge Carriers Research Articles

Hierarchically nanostructured Ag/ZnO/nBC for VOC photocatalytic degradation: Dynamic adsorption and enhanced charge transfer

The adsorption-photodegradation strategy can achieve continuous enrichment and efficient oxidation of volatile organic compounds (VOCs), but it requires a trade-off among adsorption, mass transfer, and charge transfer in this dynamic process. Therefore, the construction of an effective and stable catalytic system remains an immense challenge. Here, we report a strategy for constructing a hierarchically structured photocatalyst for efficiently degrading VOCs by assembling nanobiochar (nBC, ∼ 6.25 µm), the active center of ZnO (∼ 460 nm), and plasmonic-Ag nanoparticles (Ag NPs, ∼ 10 nm). Benefiting from its abundant surface functional groups (–OH, –CO, and –CO) and hierarchical structure-induced mesopores and macropores, VOCs can be quickly captured and dynamically diffused. Furthermore, Ag NPs build a charge transfer bridge and accumulate electrons to nBC from both the photogenerated electrons that are induced by ZnO and hot electrons from the local surface plasmon resonance (LSPR) effect of Ag NPs. Afterward, a desirable spatial separation of charge carriers and visible-light response can be achieved. Therefore, Ag/ZnO/nBC maximizes the reactive oxygen species (e.g., ·OH and ·O2−) and shows a 7.8 times higher degradation rate of formaldehyde than ZnO, and it also displays universality and stability with high photocatalytic efficiency. The photocatalytic performance was comprehensively determined based on the relative humidity, initial concentration, catalyst dose, and mass ratio of Ag NPs. This facile and universal strategy for architecting hierarchically structured photocatalysts provides an approach for enhancing photocatalytic performance for VOC degradation and environmental pollution treatment.

S-scheme ZnO/WO3 heterojunction photocatalyst for efficient H2O2 production

• ZnO/WO 3 step-scheme (S-scheme) H 2 O 2 -production photocatalyst prepared. • The ZnO/WO 3 samples with high photocatalytic H 2 O 2 -production activity. • In-situ irradiated XPS measurements investigation on S-scheme mechanism. • Advantages of S-scheme heterojunction in H 2 O 2 -production discussed. Designing highly efficient photocatalyst for hydrogen peroxide (H 2 O 2 ) production is an ideal strategy to avoid the shortcomings of traditional H 2 O 2 production and to realize the conversion of solar energy to chemical energy. In this work, a step-scheme (S-scheme) heterojunction photocatalyst composed of ZnO and WO 3 is carefully prepared by hydrothermal and calcination method for efficient photocatalytic H 2 O 2 production. The ZW30 composite photocatalysts exhibit enhanced activity with the highest H 2 O 2 -production rate of 6788 μmol L −1 h −1 . The results show that the photocatalytic H 2 O 2 production process is dominated by a direct two-electron O 2 reduction pathway. The enhanced photocatalytic H 2 O 2 -production activity is attributed to the formation of interfacial internal electric field (IEF) in the S-scheme heterojunction, which boosts the spatial separation of charge carriers and enables electrons with the strongest reduction power to participate in H 2 O 2 production. This work provides an in-depth insight of the great advantages of S-scheme heterojunction in photocatalytic H 2 O 2 production. Benefiting from the formation of the S-scheme heterojunction of ZnO and WO 3 , the useful electrons on the conduction band of ZnO and holes on the valence band of WO 3 can be efficiently spatially separated, leading to high photocatalytic production of H 2 O 2 . The S-scheme heterojunction presents great advantages for efficient H 2 O 2 production.

Rationally designed Ta3N5/BiOCl S-scheme heterojunction with oxygen vacancies for elimination of tetracycline antibiotic and Cr(VI): Performance, toxicity evaluation and mechanism insight

S-scheme heterojunction photocatalysts have been the “stars” in the field of photocatalysis. Herein, a novel S-scheme heterojunction of Ta3N5/BiOCl with oxygen vacancies (OVs) was fabricated via a facile method. The charge separation and transport mechanism of this Ta3N5/BiOCl S-scheme heterojunction was verified by the analyses of band energy structures, active species, photoelectric behaviors and DFT theoretical calculation. Compared with Ta3N5 and BiOCl, the Ta3N5/BiOCl unveils substantially upgraded photocatalytic property under visible light, and the photocatalytic efficiency for removal of tetracycline (TC) and hexavalent chromium (Cr(VI)) reaches 89.6% and 91.6%, respectively. The substantial enhancement of the photocatalytic activity is attributed to the synergistic effect of the S-scheme hetero-structure and oxygen vacancies, which improves the visible-light absorption, while promoting the spatial separation of charge carriers with the optimum redox capacity, thereby boosting the production of active species for catalytic reactions. The TC degradation pathway is deduced and the toxicity evolution of TC is appraised using the QSAR method. In a nutshell, this work gives a deep understanding of the photocatalytic mechanism based on Ta3N5/BiOCl as well as presents a newfangled thought for developing highly efficient S-scheme heterojunction photocatalysts for water decontamination.

Boosted spatial charge carrier separation of binary ZnFe2O4/S-g-C3N4 heterojunction for visible-light-driven photocatalytic activity and antimicrobial performance.

A potential method for removing toxins from contaminated wastewater, especially organic pollutants, is photo-catalysis. Here, a simple technique for producing zinc ferrite nanoparticles (ZnFe2O4 NPS) with varying quantities of sulphur doped graphitic carbon nitride nanocomposites (ZnFe2O4/S-g-C3N4 NCs) has been described. Then, using X-ray diffraction (XRD), TEM, EDX, XPS, photocurrent response, EIS, and Fourier Transform Infrared spectroscopy (FT-IR), the photo-catalytic activity of the produced nanoparticles (NPs) and nanocomposites (NCs) was examined and evaluated. The photo-catalytic activity of ZnFe2O4/S-g-C3N4 NCs was compared to a model pollutant dye, methylene blue, while degradation was evaluated spectrophotometrically (MB). Solar light has been used through irradiation as a source of lighting. The photocatalytic behaviour of the ZnFe2O4/S-g-C3N4 NCs photocatalyst was superior to that of genuine ZnFe2O4 and S-g-C3N4, which was attributed to synergic effects at the ZnFe2O4/S-g-C3N4 interconnection. Antimicrobial activity of ZnFe2O4/S-g-C3N4 against Gram-positive and Gram-negative bacteria under visible light was performed. In addition, these ZnFe2O4/S-g-C3N4 NCs show a lot of promise as an antibacterial agent.

Amorphous/crystalline heterojunction interface driving the spatial separation of charge carriers for efficient photocatalytic hydrogen evolution

The basic energy conversion in the photosynthetic system is the process of separation, transfer and utilization of photogenerated charges. Here, an amorphous/crystalline heterojunction photocatalyst with spatial separation effect is prepared by assembling graphdiyne (GDY) flakes onto MoS2–CdS nanodumbbells. Graphdiyne flexible flakes were synthesized via a Glazer-Hay coupling reaction using cuprous bromide (CuBr) as a catalyst. One-dimensional MoS2–CdS nanodumbbells with symmetrical amorphous MoS2 tips can effectively promote the separation of electrons and holes in space, attracting photogenerated electrons to move along the one-dimensional nanorods. The GDY two-dimensional flexible sheet, which can promote the outward movement of photogenerated holes and isolate the surface oxidation sites, is like a “protective suit” on the dumbbell structure, thereby improving the resistance to photocorrosion. The MoS2–CdS/GDY-10% composite photocatalyst shows the highest photocatalytic water splitting activity of graphdiyne applied to photocatalytic systems so far, and the highest hydrogen production rate can reach 17.99 mmol g−1h−1, which is 161 times that of pure CdS. The conversion efficiency of solar energy to hydrogen energy can reach 3.2%. The highest quantum efficiency is 6.48% at 450 nm. The synergistic effect of the special spatial structure and the amorphous/crystalline heterojunction can significantly reduce the recombination of electron-hole pairs and prolong the lifetime of photogenerated carriers. This work inspires the construction of graphdiyne-based photocatalysts with high activity and high stability, demonstrating the promising future of graphdiyne for photocatalytic water splitting.

Tunable strongly interacting dipolar excitons in hybrid perovskites

We study theoretically the excitonic nonlinearity in hybrid organic-inorganic Ruddlesden-Popper perovskite thin films. The composite layered structure of these materials allows for flexible modulation of their excitonic response between the limiting cases of single atomic layer and wide quasi-two-dimensional quantum well. In particular, we demonstrate that transverse electric field leads to the spatial separation of charge carriers within the inorganic layer, giving rise to strongly interacting excitons possessing built-in dipole moment. Combined with exciton binding energy of the order of hundreds of meVs, this makes hybrid perovskites an optimal platform for tailoring of nonlinear optical response at reduced dimensionality.

Fabrication of Bi12GeO20/Bi2S3 hybrids with surface oxygen vacancies by a facile CS2-mediated manner and enhanced photocatalytic performance in water and saline water

A series of biphasic hybrids Bi12GeO20/Bi2S3 containing surface oxygen vacancies (OVs) were constructed through a facile CS2-mediated manner. Microstructural, morphological, optical, and electrochemical features of relevant samples were thoroughly researched by a sequence of analytical techniques. The presence of in-situ generated Bi2S3 phase and simultaneous formation of surface OVs were confirmed in these n-p heterojunction hybrids. As soon as exposed to visible light, as-achieved hybrids provided reinforced photocatalytic removal upon dye Rhodamine B (RhB) and antibiotic tetracycline hydrochloride (TC) in comparison to bare Bi12GeO20, chiefly crediting to augmented visible-light harvesting, efficient spatial separation of charge carriers over interface by n-p heterojunction with well-matched band structures, and presence of sufficient surface OVs. Moreover, reactive Cl species and Cl-contained intermediates were undetectable in saline water, therefore the significantly enhanced catalytic efficiencies in saline water than in water were mainly attributed to different degradation routes by ultraviolet-visible (UV–Vis) absorption, three-dimension excitation emission matrix fluorescence (3D-EEM), and high performance liquid chromatograph-mass (HPLC-MS) spectra, further ascribing to partial consumption of holes by Cl- anions and boosted generation of superoxide (∙O2–) and hydroxyl (∙OH) radicals. Eventually, a reasonable photocatalysis mechanism was proposed in a Z-scheme model by these robust hybrids with favorable recyclability and structural steadiness. This work provided promising Bi12GeO20/Bi2S3 hybrids with appropriate physicochemical properties and reinforced photocatalytic degradation of organic contaminants in saline water without the generation of toxic Cl-containing intermediates.

Rational construction of 1D/2D Cu-NiS/S-g-C3N4 binary nanocomposites heterojunction enriching spatial charge carrier separation under visible light irradiation

Due to their potential to accelerate photoinduced electron/hole pair transportation, a well-defined heterojunction between the two different semiconductors was shown to improve photocatalytic performance. As a result, research has focused on building and improving heterojunctions utilizing a variety of semiconductor-based materials to improve photocatalytic activity using a variety of ways. For this purpose, g-C3N4 (CN) is being studied as a possible photocatalytic material for the removal of organic dyes, although its high recombination rate of photogenerated charge carriers limits its use. In the current work, we used a self-assembly method to create heterojunction of 5CuNS-18-SCN binary nanocomposites (NCs). The 5CuNS-18-SCN binary NCs were confirmed by XRD data. TEM examination reveals that the binary NCs are made up of Cu–NiS (CuNS) nanorods (NRs) and nanosheets (NSs), like the morphology of S-g-C3N4 (SCN). Even though the bandgap of SCN is 2.70 eV, the 5CuNS-18-SCN binary NCs shift the bandgap to 2.64 eV. Because of the well-defined heterojunction, the electron-hole pair recombination rate in the 5CuNS-18-SCN binary NCs is greatly decreased, as shown by photoluminescence spectrum analysis. The photoelectrochemical results show that 5CuNS-18-SCN binary NCs increases the photocurrent to 0.65 mA and effectively suppress the electron-hole pairs that were previously associated with bare NiS, CuNS, and SCN. Under visible light irradiation, the 5CuNS-18-SCN binary NCs effectively increased methylene blue (MB) decolorization to 100% for 36 min.

Rational catalyst design for spatial separation of charge carriers in a multi-component photocatalyst for effective hydrogen evolution

This manuscript comprehensively reviews the effect of spatial separation of charge carriers and novel strategies to achieve spatially separated active sites for enhancing photocatalytic hydrogen evolution over different photocatalyst systems.

Crystal Facet Engineering and Hydrogen Spillover-Assisted Synthesis of Defective Pt/TiO2-x Nanorods with Enhanced Visible Light-Driven Photocatalytic Activity.

Hydrogen spillover can assist the introduction of defects such as Ti3+ and concomitant oxygen vacancies (VO) in a TiO2 crystal, thereby inducing a new level below the conduction band to improve the conductivity of photogenerated electrons and the visible light absorption property of TiO2. Meanwhile, crystal facet engineering offers a promising approach to achieve improved activity by influencing the recombination step of the photogenerated electrons and holes. In this study, with the aim of achieving enhanced visible light-driven photocatalytic activity, rutile TiO2 nanorods with different aspect ratios were synthesized by crystal facet engineering, and Pt-deposited TiO2-x nanorods (Pt/TNR) were then obtained via reduction treatment assisted by hydrogen spillover. The reduction treatment at 200 °C induced the formation of surface Ti3+ exclusively, whereas surface Ti3+ and VO were formed by performing the reduction at 600 °C. The Pt/TNR with a higher aspect ratio reduced at 200 °C exhibited the highest activity in photocatalytic H2 production under visible light irradiation owing to the synergistic effect of the introduction of Ti3+ defects and the spatial charge carrier separation induced by crystal facet engineering.

Binary Co@ZF/S@GCN S-scheme heterojunction enriching spatial charge carrier separation for efficient removal of organic pollutants under sunlight irradiation

The hydrothermal approach was used to create a binary Co@ZF/S@GCN step-scheme (S-scheme) photocatalyst system. Cutting-edge devices such as TEM, XRD, XPS, FTIR, BET, UV–vis, transient photo-response, ESR signals, and EIS were used to analyze the hybrid photocatalyst. Combining 5% Co-doped zinc ferrite (Co@ZF) nanoparticles (NPs) with varying amounts (10–80 wt%) of S-g-C3N4 (S@GCN) yielded a series of binary nanocomposites (NCs). For photocatalytic dye removal, novel binary NCs built between Co@ZF and S@GCN create an enormous number of catalytic active positions. The results demonstrated that loading 5% Co@ZF NPs on S@GCN, which functions as a well-defined heterointerface for adequate charge transit and separation over the S-scheme Co@ZF/S@GCN NCs, resulted in a well-defined heterointerface. The loading of 5% Co@ZF NPs supports enhancing the BET surface area of the binary system for the photocatalytic response, boosting the sunlight harvesting capability and thereby improving the photocatalytic activity of the system. The binary hybrid photocatalyst system with optimal loading of 50% Co@ZF NPs showed the highest photo-removal efficiency (99%), which is about 2.5 times higher than those of their counterparts. Moreover, the trapping experiments revealed that •OH- and h+ were the main active species in the process of MB aqueous photo-degradation.

Ag and MOFs-derived hollow Co3O4 decorated in the 3D g-C3N4 for creating dual transferring channels of electrons and holes to boost CO2 photoreduction performance

The rapid recombination of photoinduced charge carriers and low selectivity are still challenges for the CO2 photoreduction. Herein, we proposed that ZIF-67-derived Co3O4 hollow polyhedrons (CoHP) were embedded into NaCl-template-assisted synthesized 3D graphitic carbon nitride (NCN), subsequently, loading Ag by photo-deposition as efficient composites (CoHP@NCN@Ag) for CO2 photoreduction. This integration simultaneously constructs two heterojunctions: p-n junction between Co3O4 and g-C3N4 and metal–semiconductor junction between Ag and g-C3N4, in which Co3O4 and Ag serve as hole (h+) trapping sites and electron (e-) sinks, respectively, achieving spatial separation of charge carriers. The donor–acceptor structure design of NCN realize a good photogenerated e--h+ separation efficiency. The mesoporous structure of hollow Co3O4 facilitate gas-diffusion efficiency, light scattering and harvesting. And the introduction of plasmonic Ag further strengthens the light-harvesting and charge migration. Benefiting from the rational design, the optimized ternary heterostructures exhibit a high CO2-CO yield (562 μmol g−1), which is about 4-fold as high as that of the NCN (151 μmol g−1). Moreover, the conjectural mechanism was systematically summarized. We hope this study provides a promising strategy for designing efficient g-C3N4 systems for the CO2 photoreduction.

Triple-Channel Charge Transfer over W18O49/Au/g-C3N4 Z-Scheme Photocatalysts for Achieving Broad-Spectrum Solar Hydrogen Production.

Z-scheme heterojunctions are fundamentally promising yet practically appealing for photocatalytic hydrogen (H2) production owing to the enhanced redox power, spatial separation of charge carriers, and broad-spectrum solar light harvesting. The charge-transfer dynamics at Z-scheme heterojunctions can be accelerated by inserting charge-transfer mediators at the heterojunction interfaces. In this study, we introduce Au nanoparticle mediators in the Z-scheme W18O49/g-C3N4 heterostructure, which enables an improved H2 production rate of 3465 μmol/g·h compared with the direct Z-scheme W18O49/g-C3N4 (1785 μmol/g·h) under 1 sun irradiation. The apparent quantum yields of H2 production with W18O49/Au/g-C3N4 are 3.9% and 9.3% at 420 and 1200 nm, respectively. The improved photocatalytic H2 production activity of W18O49/Au/g-C3N4 is attributable to the triple-channel charge-transfer mechanism: channel I─Z-scheme charge transfer facilitates charge separation and increased redox power of the photoexcited electrons; channels II and III─the localized surface plasmon resonances from Au (channel II) and W18O49 (channel III) enable light harvesting extension from visible to near-infrared wavelengths.

Investigation of charge transport and band alignment of MoS2-ReS2 heterointerface for high performance and self-driven broadband photodetection

Two dimensional (2D) van der Waals heterostructures are becoming one of the ascendant research areas for semiconducting device application owing to their remarkable optoelectronic properties, which allows more functioning ability beyond its individual constituent. 2D layered materials can be easily integrated and form heterostructure due to the dangling bond free surfaces. However, for novel optoelectronic device applications, the understanding of charge carrier dynamics at the interface of heterostructures is critical and essential. Here, we demonstrate the charge transport behaviour and energy level band alignment at MoS2-ReS2 heterointerface. Interlayer coupling and charge transport behaviour are investigated by Raman and photoluminescence spectroscopy. The photoelectron spectroscopy confirms type Ⅱ band alignment between MoS2-ReS2 interface, which is required for efficient separation and transportation of charge carriers. As a proof of concept, a highly sensitive, self-biased broadband photodetector is fabricated with a responsivity of 42.61 A/W at a low bias of 1 V under the illumination of 800 nm, which is 16 fold higher than the reference pristine MoS2 photodetector. Moreover, fast rise/decay transient photoresponse (20/19 ms) strongly advocate the spatial separation of charge carriers across the interface. Our proposed work establishes the MoS2 and ReS2 as promising candidates for next-generation broadband photodetector applications.

High piezo/photocatalytic efficiency of Ag/Bi5O7I nanocomposite using mechanical and solar energy for N2 fixation and methyl orange degradation

In this work, Ag/Bi5O7I nanocomposite was prepared and firstly applied in piezo/photocatalytic reduction of N2 to NH3 and methyl orange (MO) degradation. Bi5O7I was synthesized via a hydrothermal-calcination method and shows nanorods morphology. Ag nanoparticles (NPs) were photo deposited on the Bi5O7I nanorods as electron trappers to improve the spatial separation of charge carriers, which was confirmed via XPS, TEM, and electronic chemical analyses. The catalytic test indicates that Bi5O7I presents the piezoelectric-like behavior, while the loading of Ag NPs can strengthen the character. Under ultrasonic vibration, the optimal Ag/Bi5O7I presents high efficiency in MO degradation. The degradation rate is determined to be 0.033 min−1, which is 4.7 folds faster than that of Bi5O7I. The Ag/Bi5O7I also presents a high performance in piezocatalytic N2 fixation. The piezocatalytic NH3 generation rate reaches 65.4 μmol L−1 g−1 h−1 with water as a hole scavenger. The addition of methanol can hasten the piezoelectric catalytic reaction. Interestingly, when ultrasonic vibration and light irradiation simultaneously act on the Ag/Bi5O7I catalyst, higher performance in NH3 generation and MO degradation is observed. However, due to the weak adhesion of Ag NPs, some Ag NPs would fall off from the Bi5O7I surface under long-term ultrasonic vibration, which would greatly reduce the piezoelectric catalytic performance. This result indicates that a strong binding force is required when preparing the piezoelectric composite catalyst. The current work provides new insights for the development of highly efficient catalysts that can use multiple energies.

Wet chemistry synthesis of CuFe2O4/CdSe heterojunction for enhanced efficient photocatalytic H2 evolution under visible irradiation

A heterostructure of CuFe2O4/CdSe was synthesized as H2 evolution photocatalyst under visible light. The optical absorption onset of the CuFe2O4/CdSe heterostructures was red-shifted to 2.30–2.48 eV, compared to that of the bare CuFe2O4 (2.55 eV), leading to better utilization of visible light. Furthermore, the CuFe2O4/CdSe samples exhibited a higher specific surface area than the bare CuFe2O4, due to the introduction of CdSe nanospheres. Compared to the bare CuFe2O4, the CuFe2O4/CdSe heterostructure promoted H2 production from water splitting. The enhanced photocatalytic performance of the CuFe2O4/CdSe catalyst was attributed to the more efficient charge separation and lower charge transfer resistance, confirmed by fluorescence decay measurements and Nyquist plots, respectively. The band alignment between CuFe2O4 and CdSe resulted in an interfacial p-n junction, which directed the electron transfer from CdSe to CuFe2O4 and the hole transfer from CuFe2O4 to CdSe, achieving improved spatial separation of charge carriers.

Zinc sulfide quantum dots/zinc oxide nanospheres/bismuth-enriched bismuth oxyiodides as Z-scheme/type-II tandem heterojunctions for an efficient charge separation and boost solar-driven photocatalytic performance

A novel zinc sulfide quantum dot (ZnS QD)/zinc oxide (ZnO) nanosphere/bismuth-enriched bismuth oxyiodide (Bi4O5I2) tandem heterojunction photocatalyst is fabricated through two-step solvothermal, calcination and one-step hydrothermal strategies. The successfully constructed core-shell nanostructure can increase the interface area and the active sites of the composite photocatalysts. The formation of a Z-scheme/Type-II tandem heterojunction favors the transfer and spatial separation of charge carriers, in which Bi4O5I2 plays a bridging role to connect ZnO and ZnS. Simultaneously, the participation of Bi4O5I2 significantly shortens the band gap of the composite photocatalyst. This dual functional ZnO@Bi4O5I2/ZnS composite photocatalyst has a high photocatalytic hydrogen evolution rate of 578.4 µmol g−1h−1 and an excellent photocatalytic degradation efficiency for bisphenol A (BPA) and 2,4,5-trichlorophenol (TCP). In addition, cycling tests show that ZnO@Bi4O5I2/ZnS has a high stability, which is favorable for practical applications. This novel ZnO@Bi4O5I2/ZnS Z-scheme/Type-II tandem heterojunction photocatalyst will provide new ideas for the multichannel charge transfer of other highly efficient heterojunction photocatalysts.

High sensitive and stable self-powered solar-blind photodetector based on solution-processed all inorganic CuMO2/Ga2O3 pn heterojunction

Solar-blind photodetection systems, which can convert solar-blind deep ultraviolet light into an electrical signal, have been designed for practical use owing to their high sensitivity and accuracy. As one of the most suitable semiconductors for solar-blind photodetection, β-Ga2O3 can construct a pn type photodetector with another semiconductor material to meet the demands of energy savings, miniaturization and high efficiency. As a kind of natural p-type material, delafossite semiconductor materials CuMO2 (M = Al3+, Ga3+, In3+, Cr3+) have attracted much attention recently. The band alignment of CuMO2 is staggered with that of n-type β-Ga2O3; hence, the photogenerated electrons and holes tend to transfer through the interface in the opposite directions, resulting in spatial separation of charge carriers. Meanwhile, the fast hole diffusion coefficient (10−2–101 cm2 V−1 s−1) of CuMO2 guarantees the transport of holes, which is difficult in β-Ga2O3 owing to its intrinsic electronic structure. More importantly, compared with the widely used p-type materials, CuMO2 materials are almost insensitive to UVA light owing to the forbidden intrinsic direct transitions between the conduction and valence bands. Hence, the CuMO2/β-Ga2O3 pn junction photodetector exhibits high sensitivity, and the working spectral region is not extended to the UVA region. In this study, n-β-Ga2O3/p-CuMO2 (M: Ga3+, Cr3+) pn junction photodetectors were prepared by a simple solution process method. Due to the high crystallinity of the as-grown CuGaO2 and CuCrO2, the CuGaO2/β-Ga2O3 and CuCrO2/β-Ga2O3 pn junction photodetectors demonstrate an ultralow off state current of 51/61 fA, a superhigh on-to-off state current ratio of 2.3 × 104/3.5 × 104 and a high rejection ratio (R254/R365) of 2 × 104/2.8 × 104 under a bias of 0 V. The CuMO2/β-Ga2O3 pn junction photodetector satisfies the requirements of high sensitivity, stable and energy saving and has wide practical application prospect in solar-blind detection systems.

HI-Light: A Glass-Waveguide-Based "Shell-and-Tube" Photothermal Reactor Platform for Converting CO2 to Fuels.

SummaryIn this work, we introduce HI-Light, a surface-engineered glass-waveguide-based “shell-and-tube” type photothermal reactor which is both scalable in diameter and length. We examine the effect of temperature, light irradiation, and residence time on its photo-thermocatalytic performance for CO2 hydrogenation to form CO, with a cubic phase defect-laden indium oxide, In2O3-x(OH)y, catalyst. We demonstrate the light enhancement effect under a variety of reaction conditions. Notably, the light-on performance for the cubic nanocrystal photocatalyst exhibits a CO evolution rate at 15.40 mmol gcat−1 hr−1 at 300°C and atmospheric pressure. This is 20 times higher conversion rate per unit catalyst mass per unit time beyond previously reported In2O3-x(OH)y catalyst in the cubic form under comparable operation conditions and more than 5 times higher than that of its rhombohedral polymorph. This result underscores that improvement in photo-thermocatalytic reactor design enables uniform light distribution and better reactant/catalyst mixing, thus significantly improving catalyst utilization.

Robust Z-scheme g-C3N4/WO3 heterojunction photocatalysts with morphology control of WO3 for efficient degradation of phenolic pollutants

Z-scheme g-C3N4/WO3 heterojunction photocatalysts with morphology control of WO3 are facilely fabricated via a thermal-induced self-polymerization of melamine in the presence of WO3 nanowires, nanosheets and microflowers, and they are successfully applied in simulated sunlight photocatalytic degradation of two refractory phenolic pollutants, p-nitrophenol and methylparaben. The g-C3N4/WO3 heterojunctions exhibit enhanced photocatalytic removal efficiency towards the target pollutants in comparison of pristine g-C3N4 and WO3; moreover, both the ratio and morphology of WO3 influence the photocatalytic activity of g-C3N4/WO3 dramatically. At the same ratio of WO3 in heterojunctions, g-C3N4/WO3 nanowires exhibit the highest pollutants removal efficiency among three heterojunction photocatalysts. By combination of testing results including photoelectronchemistry, photoluminescence and active species trapping it is confirmed that the unique Z-scheme band alignment of g-C3N4/WO3 heterojunctions plays the dominated role to the enhanced photocatalytic activity, which not only boosts the spatial separation of charge carriers but also endows the g-C3N4/WO3 with supreme redox capacity; additionally, intimate interfacial contact between WO3 and g-C3N4 in the heterojunctions can further promote this Z-scheme-dictated charge carrier transfer and separation. Under the attack of active species like hVB+, O2− and OH radicals, the target pollutants can be oxidized deeply to harmless inorganic compounds.