Valence Band Edge Potential Research Articles

Transforming sunlight through ultrasonically engineered ZnO and g-C₃N₄ Z-scheme heterostructure for superior photocatalysis: Experimental and theoretical study

In this study, we enhanced ZnO photocatalytic activity by synthesizing nanostructures with high aspect ratio of exposed polar facets. Post-synthesis ultrasonication induced morphological reconfiguration, improving optoelectronic properties, charge carrier separation, photocurrent, and shifted the valence band edge potential to higher positive values, providing a heightened overpotential for hydroxyl radical formation. The resulting overpotential for hydroxyl radical formation significantly boosted phenol degradation under UV light. To extend photoresponse, we employed ultrasonication to create a direct Z-scheme heterostructure with gCN, preventing particle aggregation. The S-ZnO/gCN photocatalyst, exhibiting a highly ordered structure, demonstrated superior photocatalytic activity under solar light for phenol degradation. Experimental results showed that increased dissolved oxygen accelerated hydroquinone and catechol formation, enhancing phenol degradation. Experimental results were supported by theoretical calculations. This innovative approach not only improves ZnO photocatalytic activity but also broadens its application to solar light-driven reactions.

Electronic properties and applications of MoSSe/MoSTe heterostructure in photocatalytic water splitting

Monolayer material’s electronic properties can be controlled by constructing heterostructures, such as transition metal dichalcogenides (TMDCs) heterostructures. Among them, heterostructures with a new direct Z-scheme electronic band structure are promising solar-driven water splitting photocatalysts. In this work, the first principle calculation based on Density functional theory (DFT) was used to study the structure, electrical properties and optical properties of MoSSe/MoSTe heterostructures. By vertically stacking MoSSe and MoSTe monolayers and via lattice relaxation, 12 different MoSTe/MoSSe heterostructure models have been constructed. Model 1 (TeMoS/SeMoS) and model 2 (SMoTe/SMoSe) are novel direct Z-scheme heterostructure and traditional type II band configurations, respectively. Compared to type II heterostructures, direct Z-scheme arrangement can achieve more efficient spatial separation of photogenerated carriers, increase the lifetime of minority carriers while retaining the redox ability of internal carriers. And compared to monolayer materials, MoSTe/MoSSe heterostructures exhibit stronger and broader optical absorption. Additionally, the conduction band edge potential of MoSTe in the heterostructure is negative to the H+/H2O electrode potential, and the valence band edge potential of MoSSe is positive to the O2/H2O electrode potential. It can be inferred that MoSTe/MoSSe heterostructure has strong reduction and oxidation capabilities, and can achieve total water-splitting reaction. Further Gibbs free energy calculation found that the MoSSe/MoSTe heterostructure can spontaneously conduct thermodynamic water splitting under the light in both acidic and neutral environments, and the theoretical hydrogen production efficiency is 16.7 %.

Study of brush coating and spin coating on stannic oxide thin film for the electron transport layer in a perovskite solar cell

This work addresses the challenges associated with using brush coating as a cost-effective and rapid method for large-scale deposition instead of applying a spin coating for the large-scale production of solar cells. This study used brush coating and spin coating techniques to coat a 0.1 M precursor solution onto a cleaned glass substrate. Brush coating utilized a fibril brush, followed by thermal annealing at 180 °C for 1 min, while the spin coating was performed at 1000 RPM for 10 s. Compositional analysis was conducted using Electron Diffraction X-ray (EDAX), and structural analysis employed X-ray Diffraction (XRD). The EDAX analysis confirmed the presence of stannic oxide and XRD data indicated a tetragonal crystal structure of SnO 2, matched with standard data. Scanning Electron Microscopy (SEM) examination revealed that the spin-coated film surface morphology was more effective than the brush-coated film. Additionally, the brush-coated sample demonstrated superior morphology and crystallinity compared to previous research. The optical bandgap, conduction band and valence band edge potentials were determined by UV-spectroscopy. The spin-coated sample exhibited values of 4.02, −1.33 and 2.69 eV, respectively, while the brush-coated sample showed values of 3.98, −1.31 and 2.67 eV, respectively. The valence band maximum and conduction band minimum binding energies were determined using the core level binding energy in the XPS spectroscopy data. Overall, brush coating and spin coating exhibited similarities with minor differences. We may infer that the main drawback of this approach lies in the surface morphology, which can be mitigated through careful management of the coating rate and heat treatment.

GaN-WSSe'nin Dikey Gerinim Altında Fotokatalitik Performansının İncelenmesi

The application of mechanical strain is a crucial technique to adjust and optimize the physical properties of materials, making them potentially useful for various applications, including renewable energy resources and nanoelectronics. Hydrogen production through water splitting has been proposed as a promising solution to the energy crisis. Therefore, there is a great demand for exploring low-cost and efficient photocatalysts for this process. We investigated the electronic properties, structural properties and band alignment of WSSe/graphene-like GaN (g-GaN) heterostructure. Our results reveal that the band alignment of the AA-stacked WSSe/g-GaN heterostructure satisfies the water redox potentials at a pH of 7. In order to investigate the effect of regulation on these two heterostructures, out of plane strain ranging from -2% to 2% is applied. Results show that applying strain to the heterostructure will enhace the photocatalytic properties which was evaluated based on the valence and conduction band edge potentials.

Design and construction of a double Z-scheme CdS@g-C3N4/Bi2MoO6 ternary nanocomposite: Photocatalytic degradation in visible light, adsorption and electrochemical applications

Improved photocatalytic performances can be achieved by synthesizing double heterojunction nanocomposites with suitable conduction band (CB) and valence band (VB) edge potentials. In the current study, a hydrothermal approach was used to successfully synthesize a Z-scheme CdS@g-C3N4/Bi2MoO6 (CdS@GB) ternary nanocomposite with varied CdS contents. The photocatalytic efficiency of the as-synthesized materials was determined by studying the degradation of Rhodamine B (RhB) and Acetaminophen (ACM) pollutants. The experimental results revealed that 15 wt% CdS@GB (15CdS@GB) ternary composite showed the highest photocatalytic performance indicating 98.8 and 83% degradation of RhB and ACM in 35 and 140 min of irradiation, respectively. The stability of the ternary composite was also relatively high even after four consecutive cycles of photodegradation. The main reactive species involved in photodegradation processes was O2•- as revealed by the quenching experiments. The nitro blue tetrazolium (NBT) experiment further confirmed it, which showed the high production of O2•- in the reaction mixture. The synthesized ternary composites were used to study the dark adsorption of RhB, and the results confirmed the applicability of the Langmuir isotherm model. The electrochemical properties of the synthesized materials were investigated using electrochemical impedance spectroscopy (EIS) and cyclovoltammetry (CV). The results showed that 15CdS@GB has the lowest charge-transfer resistance and highest specific capacitance. Based on the findings, a double Z-scheme mechanism route was designed and presented to explain the photodegradation of the target pollutants.

Synthesis, crystal structure and photocatalytic activity of new Dion-Jacobson type titanoniobates

New Dion-Jacobson type layered perovskite compounds A'Ln2Ti2NbO10 (A′ ​= ​Rb, H; Ln ​= ​Pr, Nd) were synthesized for the first time. The phase and chemical purity of the compounds were proved by X-ray diffraction (XRD) and EDX. Compounds RbPr2Ti2NbO10 and RbNd2Ti2NbO10 were synthesized using solid-state reactions, whereas HPr2Ti2NbO10·1.5H2O and HNd2Ti2NbO10·2H2O were obtained from Rb-containing phases by ion-exchange reactions. Crystal structures of RbPr2Ti2NbO10 (P4/mmm, a ​= ​0.38223 (1) nm, c ​= ​1.51485 (8) nm, Rwp ​= ​3.87%) and RbNd2Ti2NbO10 (P4/mmm, a ​= ​0.38153 (1) nm, c ​= ​1.51200 (6) nm, Rwp ​= ​3.62%) were refined using the Rietveld method. The distortions of polyhedrons in the structures were studied in detail. The thermal behavior of compounds was established using DTA. The ion-exchange products were found to be metastable hydrates. Optical band gap, valence band edge and conduction band edge potentials of obtained compounds were calculated from diffuse reflectance spectroscopy data. Photocatalytic experiment of methylene blue degradation under ultraviolet (UV) light was conducted with ground synthesized compounds. The particle size distributions were measured by laser diffraction before and after grinding. RbNd2Ti2NbO10 showed the highest photocatalytic activity, while HPr2Ti2NbO10·1.5H2O and HNd2Ti2NbO10·2H2O showed none.

Intriguing electronic, optical and photocatalytic performance of BSe, M2CO2 monolayers and BSe-M2CO2 (M = Ti, Zr, Hf) van der Waals heterostructures.

Using density functional (DFT) theory calculations, we have investigated the electronic band structure, optical and photocatalytic response of BSe, M2CO2 (M = Ti, Zr, Hf) monolayers and their corresponding BSe–M2CO2 (M = Ti, Zr, Hf) van der Waals (vdW) heterostructures. Optimized lattice constant, bond length, band structure and bandgap values, effective mass of electrons and holes, work function and conduction and valence band edge potentials of BSe and M2CO2 (M = Ti, Zr, Hf) monolayers are in agreement with previously available data. Binding energies, interlayer distance and Ab initio molecular dynamic simulations (AIMD) calculations show that BSe–M2CO2 (M = Ti, Zr, Hf) vdW heterostructures are stable with specific stacking and demonstrate that these heterostructures might be synthesized in the laboratory. The electronic band structure shows that all the studied vdW heterostructures have indirect bandgap nature – with the CBM and VBM at the Γ–K and Γ-point of BZ for BSe–Ti2CO2, respectively; while for BSe–Zr2CO2 and BSe–Hf2CO2 vdW heterostructures the CBM and VBM lie at the K-point and Γ-point of BZ, respectively. Type-II band alignment in BSe–M2CO2 (M = Ti, Zr, Hf) vdW heterostructures prevent the recombination of electron–hole pairs, and hence are crucial for light harvesting and detection. Absorption spectra are investigated to understand the optical behavior of BSe–M2CO2 (M = Ti, Zr, Hf) vdW heterostructures, where the lowest energy transitions are dominated by excitons. Furthermore, BSe–M2CO2 (M = Ti, Zr, Hf) vdW heterostructures are found to be potential photocatalysts for water splitting at pH = 0, and exhibit enhanced optical properties in the visible light zones.

Strain effect on the electronic and photocatalytic properties of GaN-MSSe (M=Mo, W)

Application of strain is an important technique to tune the physical properties of materials and make them promising in renewable energy resources and nanoelectronics. Production of hydrogen from water splitting is a possible solution to the energy crises. Low cost and efficient photocatalyst is highly desired to be explored. Through first principle investigation the electronic properties, band alignment and the photocatalytic response of GaN-MoSSe and GaN-WSSe heterostructures are calculated. Different stacking of the materials are modeled and from relaxation energies the most stable material is investigated. Type-II band alignments are confirmed in these heterostructures. Switching of band alignment from type-II to Type-III is predicted in GaN-MoSSe with compressional strain. The photocatalytic behavior of these systems based on valence and conduction band edge potentials confirms that GaN-WSSe is energetically favorable at pH ​= ​0 for water splitting.

Effective photodegradation of 4-nitrophenol with CuO nano particles prepared by ionic liquids/water system

The hydrophobic ionic liquids/water two-phase system was developed to prepare CuO nano particles. The catalytic activity of the synthesized CuO was investigated by photodegradation of 4-nitrophenol (4-NP) in the presence of H2O2 under visible light irradiation. The optical properties of the synthesized CuO were characterized by ultraviolet–visible (UV–Vis) diffuse reflectance spectroscopy (DRS). Experimental results indicated that the band gap energy (Eg), conduction band edge potential (ECB) and valence band edge potential (EVB) of the synthesized CuO were 1.37 eV, 0.625 eV and 1.995 eV, respectively. A degradation efficiency of 4-NP (4.8 mmol L−1) as high as 95.3% could be achieved under the conditions of pH 6.0, 0.48 g L−1 of CuO dosage, 1.4% of H2O2 dosage and 90 min of degradation time. The synthesized CuO exhibited poor catalytic activity under alkaline conditions due to the disassociation of 4-NP, which elevated the repulsion between CuO and the 4-NP anions. The synthesized CuO nano particles exhibited higher catalytic activity compared with the catalysts reported in literature. Furthermore, the synthesized CuO nano particles could be reused at least six times without decreasing their catalytic activity. Compared with the traditional hydrothermal method, mild operating conditions and time saving are the advantages of the developed method for the preparation of CuO.

Effects of p-type (Ag, Cu) dopant on the electronic, optical and photocatalytic properties of MoS2, and impact on Au/Mo100-x-yAgxCuyS2 performance

MoS2 is an alternative of graphene due to its intriguing properties and it is necessary to modify the properties for achieving p-MoS2 and complementary device applications. Doping is one of the most prevalent techniques for modification of materials properties and fabricating p-MoS2. Herein, we report on Ag and Ag-Cu doped MoS2 investigated by theoretical and experimental studies. Detailed study of DFT highlights the confirmation of p-type MoS2. The band gap can be tuned from 1.21 to 0.51 eV (theoretically) and 1.92–1.30 eV (experimentally). The enhancement of absorption in the visible region attributed to Ag and Ag-Cu doping. The conduction band (CB) edge potential is smaller in negative than H+/H2 (0.0 eV) for undoped, Ag = 2.5% and Ag-Cu (Ag = 2.5, Cu = 10%) doped MoS2, hence the photogenerated electrons can weakly reduce H+ to produce H2. While the deeper valence band (VB) edge potential than O2/H2O (1.23 eV) confirms that the holes created upon photon absorption strongly shows the ability for water oxidation. However for other doping both potential edges are more positive which insights strong oxidative material. Interestingly, the theoretical calculation suggests that the CB edge potential should be upward shifting for enhancing the photocatalytic activity of MoS2. EDX and XPS measurements disclose the presence of Mo, S, Ag and Cu elements in the thin films. Furthermore, decreasing forward current and shifting threshold voltage (VT) toward higher voltage in (Ag, Cu) doped Au/Mo100-x-yAgxCuyS2 insights p-type MoS2. Therefore, these demonstrations could be extended its applications to be enable high-performance electronic and optoelectronic devices.

Indium sulfide-based photocatalysts for hydrogen production and water cleaning: a review

Solar illumination is a promising source of primary energy to reduce global warming and to clean polluted waters, thus fostering research of the design of efficient photocatalysts for hydrogen production by water splitting and for contaminant degradation. In particular, photocatalysis by indium sulfide (In2S3) is drawing attention due to its suitable narrow bandgap of 2.0–2.3 eV for visible light harnessing, yet large-scale application of unmodified In2S3 is limited. Here we review the photocatalyst criteria for water splitting, the synthesis and morphological manipulations of In2S3, the synthesis of heterojunctions by coupling semiconductors to increase performance, and doping In2S3. In2S3-based heterojunctions, i.e., traditional type II, all-solid-state, and direct Z-scheme photocatalytic systems show benefits such as larger charge separation, broad solar spectrum absorption, and amended conduction band and valence band edge potentials for maximum pollutant removal and H2 production. The effect of dopant incorporation on electronic modulations of In2S3 is explained by the density functional theory.

Structural, electronic, optical, thermoelectric and photocatalytic properties of SiS/MXenes van der Waals heterostructures

Vertical stacking of two-dimensional materials into layered van der Waals heterostructures are recently considered as promising candidates for optoelectronic devices because they can combine advantages of the individual 2D materials. MXenes have emerged an appealing optoelectronic material due to the desirable electronic properties. This paper focuses on the structural, electronic, optical, thermoelectric and photocatalytic properties of SiS, Ti2CO2, Zr2CO2, Hf2CO2 monolayers and their corresponding van der Waals (vdW) heterostructures. These materials and their heterostructures are dynamically stable. All unstrained heterostructures show indirect band gap semiconductors except SiS-Ti2CO2 which exhibits metallic nature. The higher carrier mobility of the metallic, SiS-Ti2CO2 is followed by its least effective mass. The induction of considerable biaxial (compressive and tensile) strain offers metallic characteristics to SiS-Ti2CO2 and SiS-Zr2CO2 while SiS-Hf2CO2 retains its semiconducting nature. SiS-Zr2CO2/SiS- Hf2CO2 show type-I/type-II band alignment which are highly suitable for electronic, optical, nanoelectronic and optoelectronic devices. Additionally, the least effective mass of SiS-Zr2CO2 offers higher carrier mobility. Bader charge analysis revealed that MXenes dissipate the charge carriers to SiS monolayer. Furthermore, a good comparison of thermoelectric performance of all the systems illustrates their significant power factor that is well interpreted at 300 K and 800 K. Several excitonic peaks are observed of the systems in the visible region of solar spectrum. Furthermore, valence (conduction) band edge potentials are calculated to understand the photocatalytic behavior of these systems.

Efficient solar-light-driven photoelectrochemical water oxidation of one-step in-situ synthesized Co-doped g-C3N4 nanolayers

Cobalt-doped g-C3N4 (Co-g-CN) nanolayers were prepared by a single-step thermal treatment with urea and cobalt nitrate. Different amounts of cobalt nitrate were tested to optimize the amount of cobalt dopant in the g-C3N4 (g-CN) matrix. Several characterization methods were used to explore the structural and optical properties along with the photoelectrochemical (PEC) performance. X-ray diffraction and Fourier transform infrared studies confirmed that g-CN nanolayers were successfully doped with cobalt without disturbing the basic 2-D structure and tris-triazine units of g-CN. Furthermore, microscopy images demonstrated that the cobalt effectively transformed the short nanosheets into long nanolayers. The cobalt-doping enhanced the visible absorption of g-CN and tuned the bandgap from 2.71 to 2.62 eV. An X-ray photoelectron spectroscopy (XPS) investigation discovered that cobalt entered into the g-CN network as Co2+ ions. XPS valence band spectra gave information on the modification in the valence and conduction band edge potentials due to cobalt doping. The photoluminescence intensity from the Co-g-CN samples was lesser than that from g-CN nanosheets, and the PEC activity of the Co-g-CN nanolayers was greater than that of as-prepared g-CN nanosheets. Co-g-CN samples prepared with 15 mg of cobalt nitrate hexahydrate showed a PEC performance of 3.2522 mA/cm2, which was greater than that of g-CN nanosheets (1.9246 mA/cm2). The better PEC performance was ascribed to the synergistic consequence of the higher visible absorption obtained by tuning the bandgap and the host–guest interactions between cobalt and g-CN.

Electronic structure and photocatalytic properties of H, F modified two-dimensional GeTe

Using the first principle calculation based on the density functional theory, we have systematically investigated the structure stability, electronic structure and photocatalytic properties of two-dimensional single-layered GeTe crystal structure modified by H and F. The results show that the lattice constant, bond angle and bond length of GeTe increase after being modified. The stability analysis shows that all the materials have excellent dynamical, mechanical, and thermal stabilities. The electronic structure analysis shows that the two-dimensional GeTe is an indirect bandgap semiconductor with an energy gap of 1.797 eV, and its energy band is mainly composed of Ge-4p and Te-5p, while it is converted into a direct bandgap semiconductor by H or F modification and H-F co-modification (F and Ge on one side, H and Te on the other), and their corresponding energy gaps are reduced to 1.847 eV (fH-GeTe), 0.113 eV (fF-GeTe) and 1.613 eV (hF-GeTe-hH). However, hH-GeTe-hF is still an indirect band gap semiconductor, and its energy gap is reduced to 0.706 eV. The results of the density of states show that part of the Ge-4p and Te-5p electrons are transferred to a deeper level due to the adsorption of H or F atoms, resulting in a strong orbital hybridization between them and the adsorbed atoms. The effective mass shows that the effective mass of H or F modified and H-F co-modified GeTe (F and Ge on one side, H and Te on the other) decrease, and their carrier mobilities increase. The carrier recombination rates of all modified GeTe materials are lower than that of the intrinsic GeTe, so the semiconductor will be more durable. The electron density difference shows that due to the electronegativities of atoms being different from each other, when H or F is used to modify GeTe, some electrons transfer to H and F atoms, resulting in the weakening of covalent bond between Ge and Te atoms and the enhancement of ion bond. The results of band-edge potential analysis show that GeTe can produce hydrogen and oxygen by photolysis of water. However, the valence band edge potential of the modified GeTe decreases significantly, and its oxidation ability increases considerably, the photocatalytic water can produce O<sub>2</sub>, H<sub>2</sub>, O<sub>3</sub>, OH·, etc. Optical properties show that the modified GeTe can enhance the absorption of visible and ultraviolet spectrum, which indicates that they have great application prospects in the field of photocatalysis.

Effects of annealing on bandgap and surface plasmon resonance enhancement in Au/SnO2 quantum dots

Au/SnO2 quantum dots (AuSQDs) were synthesized, and the effects of annealing on their structural and optical properties were examined. Significant changes were observed in the bandgap and surface plasmon resonance (SPR) of the AuSQDs after thermal treatment at different temperatures (400, 500, and 600 °C). The properties of the as-prepared and annealed samples were characterized via X-ray diffraction analysis, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy, and diffuse reflectance spectroscopy. Annealing reduced the bandgap from 3.03 to 2.33 eV and increased the crystallinity while maintaining an average crystallite size below 10 nm. XPS valence band (VB) profiles provided information regarding the VB edge potentials, which helped to determine the conduction band edge potentials. An enhancement in the SPR of the Au nanoparticles was observed for AuSQD-500, which had the smallest bandgap among the samples investigated.

Oxygen‐Vacancy‐Mediated Photocatalysis over Bi2Sn2O7: Exceptional Catalytic Activity and Selectivity

AbstractA series of Bi2Sn2O7 photocatalysts was developed with the aim to regulate defect chemistry as well as electronic structure by modulating the charge states of tin species for boosting photocatalytic selective oxidation of alcohols performance. Defective centers, such as oxygen vacancies (OVs), were beneficial to enhancing the adsorption and activation of molecular oxygen. Meanwhile, the valence band edge potential of Bi2Sn2O7 with higher OVs content exhibited a distinct downshift, improving the thermodynamical driving force of photooxidation. Additionally, OVs contributed to promoting the separation efficiency of photogenerated carriers, which can be confirmed by the surface photovoltage measurement. By optimizing the electronic structure as well as defect chemistry, the optimal benzyl alcohol conversion efficiency was 76.0 % with selectivity toward benzaldehyde being about 100 %. It's found that photogenerated holes and .O2− active species played critical role in photocatalytic aerobic oxidation. This work may provide a novel insight to clarify the role of defect chemistry during the selective benzyl alcohol oxidation over Bi2Sn2O7 photocatalyst.

Facile one-step synthesis of pellet-press-assisted saddle-curl-edge-like g-C3N4 nanosheets for improved visible-light photocatalytic activity

Abstract Graphitic carbon nitride (g-C 3 N 4 ) has attracted increasing interest as a visible-light-active photocatalyst. In this study, saddle-curl-edge-like g-C 3 N 4 nanosheets were prepared using a pellet presser (referred to as g-CN P nanosheets). Urea was used as the precursor for the preparation of g-C 3 N 4 . Thermal polymerization of urea in a pellet form significantly affected the properties of g-C 3 N 4 . Systematic investigations were performed, and the results for the modified g-C 3 N 4 nanosheets are presented herein. These results were compared with those for pristine g-C 3 N 4 to identify the factors that affected the fundamental properties. X-ray diffraction analysis and high-resolution transmission electron microscopy revealed a crystallinity improvement in the g-CN P nanosheets. Fourier-transform infrared spectroscopy provided clear information regarding the fundamental modes of g-C 3 N 4 , and X-ray photoelectron spectroscopy (XPS) peak-fitting investigations revealed the variations of C and N in detail. The light-harvesting property and separation efficiency of the photogenerated charge carriers were examined via optical absorption and photoluminescence studies. The valence band edge and conduction band edge potentials were calculated using XPS, and the results indicated a significant reduction in the bandgap for the g-CN P nanosheets. The Brunauer–Emmett–Teller surface area increased for the g-CN P nanosheets. The photocatalytic degradation performance of the g-CN P nanosheets was tested by applying a potential and using the classical dye Rhodamine B (RhB). The RhB dye solution was almost completely degraded within 28 min. The rate constant of the g-CN P nanosheets was increased by a factor of 3.8 compared with the pristine g-C 3 N 4 nanosheets. The high crystallinity, enhanced light absorption, reduced bandgap, and increased surface area of the saddle-curl-edge-like morphology boosted the photocatalytic performance of the g-CN P nanosheets.

Enhanced photoelectrochemical performance of InGaN-based nanowire photoanodes by optimizing the ionized dopant concentration

InGaN-based nanowires (NWs) have been extensively studied for photoelectrochemical (PEC) water splitting devices owing to their tunable bandgap and good chemical stability. Here, we further investigated the influence of Si doping on the PEC performance of InGaN-based NW photoanodes. The Si dopant concentration was controlled by tuning the Si effusion cell temperature (TSi) during plasma-assisted molecular beam epitaxy growth and further estimated by Mott-Schottky electrochemical measurements. The highest Si dopant concentration of 2.1 × 1018 cm−3 was achieved at TSi = 1120 °C, and the concentration decreased with further increases in TSi. The flat-band potential was calculated and used to estimate the conduction and valence band edge potentials of the Si-doped InGaN-based NWs. The band edge potentials were found to seamlessly straddle the redox potentials of water splitting. The linear scan voltammetry results were consistent with the estimated carrier concentration. The InGaN-based NWs doped with Si at TSi = 1120 °C exhibited almost 9 times higher current density than that of the undoped sample and a stoichiometric evolution of hydrogen and oxygen gases. Our systematic findings suggest that the PEC performance can be significantly improved by optimizing the Si doping level of InGaN-based NW photoanodes.

Fabricating Nano-Sized BiVO4/InVO4/g-C3N4 Photocatalysts for Efficient Degradation of Acid Blue 92 Azo Dye

BiVO4/InVO4 and BiVO4/InVO4/g-C3N4 were prepared by hydrothermal and ultrasonic-assisted hydrothermal methods respectively. All prepared samples were characterised by X-ray diffraction, scanning electron microscopy and UV-Vis diffuse reflectance spectroscopy. The photocatalytic activity of the prepared catalysts was determined by degradation of Acid Blue 92 (AB92) under visible light. The rate constant and efficiency of AB92 degradation over BiVO4/InVO4/g-C3N4 was higher than that over BiVO4/InVO4 which indicates better photocatalytic activity of BiVO4/InVO4/g-C3N4. This enhancement can be attributed to the suitable dispersion of BiVO4 and InVO4 particles on the g-C3N4 surface. Furthermore, the conduction band and valence band edge potentials of InVO4, BiVO4 and g-C3N4 extend the life-time of electron–hole pairs which is beneficial for the improvement of photocatalytic efficiency.

Programming Interfacial Energetic Offsets and Charge Transfer in β-Pb0.33V2O5/Quantum-Dot Heterostructures: Tuning Valence-Band Edges to Overlap with Midgap States

Semiconductor heterostructures for solar energy conversion interface light-harvesting semiconductor nanoparticles with wide-band-gap semiconductors that serve as charge acceptors. In such heterostructures, the kinetics of charge separation depend on the thermodynamic driving force, which is dictated by energetic offsets across the interface. A recently developed promising platform interfaces semiconductor quantum dots (QDs) with ternary vanadium oxides that have characteristic midgap states situated between the valence and conduction bands. In this work, we have prepared CdS/β-Pb0.33V2O5 heterostructures by both linker-assisted assembly and surface precipitation and contrasted these materials with CdSe/β-Pb0.33V2O5 heterostructures prepared by the same methods. Increased valence-band (VB) edge onsets in X-ray photoelectron spectra for CdS/β-Pb0.33V2O5 heterostructures relative to CdSe/β-Pb0.33V2O5 heterostructures suggest a positive shift in the VB edge potential and, therefore, an increased driving force...