Band Edge Potential Research Articles

Exploring photocatalytic and photovoltaic applications of chalcogenide Perovskites, ABS3 (A = Li, Na, K, Rb, Cs; B = Si, Ge, Sn): A First-Principles investigation using the HSE-06 hybrid functional

Unlike traditional semiconductors, chalcogenide perovskites offer a unique combination, merging the stability and safety of oxides with the tunability of halide semiconductors, making them particularly promising for photocatalytic and photovoltaic applications. This paper theoretically investigates the optoelectronic properties of the triclinic ABS3 (A = Li, Na, K, Rb, Cs; B = Si, Ge, Sn) perovskites using density functional theory with the HSE06 hybrid functional. The feasibility of synthesizing ABS3 materials was revealed using formation energy calculations. Band structure and density of state calculations confirm that all compounds under investigation are semiconductors exhibiting indirect bandgaps. These bandgaps increase with the ionic radius of the A-site cation, following the trend Li < Na < K < Rb < Cs. Additionally, the order of bandgap energies for the B-site elements is observed as Si > Sn > Ge. This trend emphasizes the significant influence of cation size on the electronic properties of perovskite materials. The investigated perovskites exhibit bandgaps between 1.67 and 3.55 eV, with a narrow difference (0.03–0.49 eV) between their indirect and direct gaps. We additionally compute various optical parameters (dielectric function, refractive index, extinction coefficient, optical conductivity, absorption coefficient, reflectivity, and energy loss function) across the 0–50 eV energy range. The valence and conduction band edge potentials of ABS3 perovskites were calculated to evaluate their potential applications in water splitting, carbon dioxide reduction, and photodegradation processes. The results of this study demonstrate that several ABS3 semiconductors exhibit promising characteristics that position them as efficient photocatalysts for these photocatalytic reactions. LiGeS3 and NaGeS3, in particular, are promising for solar cell applications.

Synthesis, Structure, and Properties of Dion–Jacobson Double‐Layered Perovskites A′SmNb2O7 (A′=Rb, K, Na, Li, H)

AbstractDion‐Jacobson‐type layered perovskite compounds A′SmNb2O7 (A′=Rb, K, Na, Li, H) were synthesized using solid‐state and ion‐exchange methods. While the parent solid‐state product RbSmNb2O7, has previously been studied, the ion‐exchanged compounds were obtained and studied for the first time. The phase and chemical purity of the compounds were confirmed by X‐ray diffraction (XRD) and energy‐dispersive X‐ray spectroscopy (EDX). The crystal structures of RbSmNb2O7 (I2 cm, a=0.54356(1) nm, b=0.53935(1) nm, c=2.1891(5) nm), KSmNb2O7 (I2 cm, a=0.53660(7) nm, b=0.54481(6) nm, c=2.1527(1) nm) and LiSmNb2O7 (B2 cm, a=0.54546(4) nm, b=0.53567(4) nm, c=2.04582(5) nm) were refined using the Rietveld method. Polyhedral distortions in these structures have been studied in detail. The thermal behavior of the compounds has been determined using differential thermal analysis (DTA), revealing that A′=Na, Li and H compounds are metastable hydrates, while A′=Rb and K compounds are stable. The optical band gap, valence band edge, and conduction band edge potentials of the compounds obtained were calculated using diffuse reflection spectroscopy data. A photocatalytic experiment was performed on the degradation of methylene blue under ultraviolet light. All of the samples obtained showed some asctivity in the reaction of dye photooxidation.

Ligand modulated charge transfers in Z-scheme configured Ni-MOF/g-C3N4 nanocomposites for photocatalytic remediation of dye-polluted water

The development of photocatalysts must be meticulous, especially when they are designed to degrade hazardous dyes that cause mutagenesis and carcinogenesis. In this meticulous approach, Ni-based metal–organic frameworks with different ligands, including terephthalic acid (NTP), 2-aminoterephthalic acid (NATP), and their composite with g-C3N4 (NTP/GCN, and NATP/GCN) have been synthesized using hydrothermal method. Structural analysis by XRD and ATR-IR revealed synergistic properties due to robust chemical interactions between the NATP-MOFs and GCN systems. A flower-like morphology was observed for both NTP and NATP, while their composites showed mixed-particulate structures mimicking the morphology of GCN. Optical analyses indicated visible-light driven properties with modulated recombination resistance in the system. Among the synthesized bare and composite systems, NATP/GCN exhibited the highest photocatalytic degradation efficiency for the cationic rhodamine B dye (~ 93% in 120 min), while it was relatively less efficient for the anionic Congo red dye, (~ 64% in 120 min). The insights gained from the fundamental characterizations including Mott–Schottky, scavenger, and electrochemical impedance analysis revealed that the amino-groups in NATP/GCN composite offered the band edge potentials suitable for the effective generation of energetic radical species with the improved carrier delocalization, recombination resistance, and charge transfer properties in the composite system through Z-scheme formation. Parametric investigations by varying the concentration of catalyst, dye, and pH along with recycle studies, demonstrated the excellent stability of the developed composites for sustainable photocatalytic applications.

Palladium based air-stable 2D penta-material’s heterostructures for water splitting applications

Heterostructures offer superior photocatalytic characteristics over their constituent counterparts due to their charge separation abilities. Here, we conduct a systematic study of a recently synthesized novel family of palladium-based pentagonal air-stable 2D monolayers, PdSe2, PdPSe, and PdPS, and their heterostructures using first-principles calculations for photocatalytic applications. Electronic band structure calculations reveal moderate bandgaps of 2.27 eV for PdSe2, 2.01 eV for PdPSe, and 2.25 eV for PdPS, indicating their suitability for photocatalytic water splitting. Moreover, to spatially separate and reduce the recombination possibility of photoinduced electron-hole pairs, we propose three van der Waals heterostructures: PdPSe/PdSe2, PdPS/PdSe2, PdPS/PdPS, with the corresponding bandgaps of 1.84 eV, 1.64 eV, and 1.65 eV, respectively. Based on work functions and the staggered band alignment of constituting monolayers, all three heterostructures are identified as type-II photocatalysts, which makes them notable photocatalyst. Additionally, band-edge potentials of PdPSe/PdSe2 and PdPS/PdSe2 confirm their suitability for overall water splitting via photocatalysis, whereas PdPS/PdPSe is suitable for oxygen evolution reactions only. The optical absorption spectra show the ability of each system to operate under a wide range of the spectrum, from visible light to high-energy (UV) regions. These characteristics make these systems valuable and attractive for photocatalytic applications.

Janus NbOBrI monolayer for efficient photocatalytic overall water splitting

Due to the presence of a built-in electric field, two-dimensional Janus materials can effectively reduce photogenerated carrier recombination while promoting carrier separation. In this work, the viability of Janus NbOBrI monolayer as a high-efficiency photocatalyst for water splitting was examined using first-principles calculations. The results demonstrate that the Janus NbOBrI monolayer exhibits appropriate band-edge potentials, significant visible light absorptions, high carrier separation efficiency and high enough carrier mobility along the Peierls distortion direction. Moreover, we have determined the variations in the Gibbs free energy for the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) at various pHs, and found that the OER can occur spontaneously in the light environment. Applying -1.5 % uniaxial strain in the a(b) direction of the NbOBrI monolayer helps to increase the reduction potential and provide sufficient power for the HER, resulting in a solar-to-hydrogen (STH) efficiency of 8.9 % (9.3 %).

Unveiling the synergistic potential of g-C3N4-MWCNT/In2O3 nanocomposite for enhanced organic pollutant degradation and cancer cell inhibition under visible light irradiation

The surge in industrial activities and a substantial increase in antibiotic usage, has led to the further deterioration of global water pollution problems. Focusing on this current scenario, we synthesize the g-C3N4-MWCNT/In2O3 (GMI) ternary composite to utilize for the photocatalytic degradation of levofloxacin (LF) antibiotic and crystal violet (CV) dye under visible light. The photocatalytic degradation of CV (15 mgL⁻1) and LF (40 mgL⁻1) was 99.7 % and 87.4 % respectively, in just 15 and 100 min of irradiation with GMI-0.2 nanocomposite. The removal rates of CV and LF with GMI-0.2 nanocomposite were 14.61 and 4.85 times more rapid than those observed with In2O3. Similarly, compared to g-C3N4, the removal rates for CV and LF were 7.34 and 3.98 times higher when using GMI-0.2 nanocomposite. The trapping experiments and ESR measurements indicated that O2•⁻ was the predominant active species responsible for the photocatalytic degradation processes. In order to explain the degradation processes, a feasible photocatalytic mechanism for GMI ternary composite was proposed. The mechanism was based on the calculations of the band gaps and edge potentials of the synthesised materials as well as the findings of the quenching experiments. The GMI-0.2 nanocomposite was also used to treat human lung cancer cells, and it was discovered that cell viability with 100 µg/mL of the photocatalyst was lowest in both dark (36 %) and in visible light (20 %).

Ligand-Engineered Structural and Physiochemical Properties of 1D Molybdenum-MOFs: A Seldom Explored System for Photocatalytic Applications.

As one of the seldom explored systems, molybdenum-based metal-organic frameworks (Mo-MOFs) with different ligands such as terephthalic acid (Mo-TA), 2-aminoterephthalic acid (Mo-ATA), benzenetricarboxylic acid (Mo-BTC), 2-methylimidazole (Mo-2MI), 2-bipyridine (Mo-2bpy), and 4-bipyridine (Mo-4bpy) were developed in this study. X-ray diffraction (XRD), Raman, and attenuated total reflectance-infrared (ATR-IR) analyses confirmed the ligand-dependent crystal structure of the Mo-MOFs along with the characteristic functional groups present in the respective systems. Interestingly, the morphology of all of these the developed Mo-MOFs was found to be a one-dimensional rod-like structure, which was attributed to the binding nature of the ligands onto the growing Mo-frameworks. Optical analysis indicated that all these Mo-MOFs exhibit ultraviolet (UV) light absorption properties with band gap energy in the range of 3.47-3.03 eV. Among the various Mo-MOFs developed, Mo-4bpy MOF degraded a maximum of ∼76 and 62% of malachite green and Congo red dyes, respectively, under sunlight irradiation. The observed improved photocatalytic efficiency of Mo-4bpy MOF was attributed to its appropriate band edge potential, confirmed by Mott-Schottky analysis, improved carrier lifetime (∼34.6 ns) estimated using the time-resolved photoluminescence (TRPL) spectrum, presence of elements with stable oxidation states in the system confirmed by X-ray photoelectron spectroscopy (XPS), improved charge transfer characteristics, and decreased recombination resistance, as confirmed by impedance and PL analyses, respectively. The degradation of Mo-4bpy MOFs mediated by superoxide (•O2-) and hydroxyl radicals (OH•) was further confirmed by scavenger studies. Cyclic studies performed for up to 5 cycles suggested that the degradation efficiency of the Mo-4bpy MOF was stable, attributed to its excellent structural, optical, and morphological features confirmed via postcharacterization of the recycled photocatalyst.

Electronic Structure and Functions of Carbon Nitride in Frontier Green Catalysis.

ConspectusGraphitic carbon nitride-based materials have emerged as promising photocatalysts for a variety of energy and environmental applications owing to their "earth-abundant" nature, structural versatility, tunable electronic and optical properties, and chemical stability. Optimizing carbon nitride's physicochemical properties encompasses a variety of approaches, including the regulation of inherent structural defects, morphology control, heterostructure construction, and heteroatom and metal-atom doping. These strategies are pivotal in ultimately enhancing their photocatalytic activities. Previous reviews with extensive examples have mainly focused on the synthesis, modification, and application of carbon nitride-based materials in photocatalysis. However, there has been a lack of straightforward and in-depth discussion to understand the electronic characteristics and functions of various engineered carbon nitrides as well as their precise tailoring strategies and ultimately to explain the regularity and specificity of their improved performance in targeted photocatalytic systems. In the past ten years, our group has conducted extensive investigations on carbon nitride-based materials and their application in photocatalysis. These studies demonstrate the close yet intricate relationship between the electronic structure of carbon nitride materials and their photocatalytic reactivity. Understanding the electronic structure and functions of carbon nitride, as well as different engineering strategies, is essential for the improvement of photocatalytic processes from fundamental study to practical applications.To this end, in this Account, we first delve into the nature of the electronic properties of carbon nitride, highlighting the electronic structures, including band structure, density of states, molecular orbitals, and band center, as well as its electronic functions, such as the charge distribution, internal electric field, and external electric force. Subsequently, based on recent research in our group, we present a detailed discussion of the strategic modifications of carbon nitride and the consequential impacts on the physicochemical properties, particularly the optical properties and intrinsic electronic characteristics, for enhancing the photocatalytic performance. These modifications are categorized as follows: (i) component changing, which involves intralayer and interface heterojunctions as well as homojunctions, to modulate the band-edge potentials and reactivity of photoinduced electrons and holes toward surface redox reactions; (ii) dimensional tuning, which engineers the dimensional structure of carbon nitride, to influence the electron transfer direction; (iii) defect and heteroatom modification, which introduces a symmetry break in the carbon nitride framework, to promote charge redistribution for altering the charge density and electronic structure; and (iv) anchoring of single-atom metals to facilitate orbital hybridization and charge transfer enhancement through the unique metal-N coordination configurations. Finally, we propose an appraisal of the prospects and challenges in the precise manipulation and characterization of the electronic structure and functions of carbon nitride. The integration of in situ electronic structure analysis, theoretical calculation based on machine learning, and precise mechanism study may propel its substantial development in the light-driven circular economy. We hope this Account aspires to offer novel insights and perspectives into the operational mechanisms and tailored structure of carbon nitride-based materials in photocatalysis.

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.

Enhanced photocatalytic hydrogen production of Ag and N-doped NaTaO3 perovskite nanocubes

In the current study, a simple hydrothermal method was used to successfully synthesize NaTaO3 and Ag, N doped NaTaO3 catalysts. The band edge potential was accessible through UV–visible spectroscopic analysis, and the diffraction peak was easily indexed as an orthorhombic structure. The values of the predicted crystallite sizes for the undoped NaTaO3, Ag-doped, and N-doped NaTaO3 nanoparticles are 61.03 nm, 48.9 nm, and 53.50 nm, respectively. Pure, Ag, and N doped NaTaO3 nanocubes were discovered to exhibit band gap energies of 3.62, 3.60, and 3.57 eV, respectively, based on the UV-Vis examination. Moreover, a Field Emission Scanning Electron Microscopy study confirmed the presence of cubic (3-D) shape. An HRTEM examination verified that the material is polycrystalline. The Ta, Na, N, and O are present at binding energies of 26.09, 1073, 405.7, and 526.6 eV, respectively, according to the XPS spectra. The pure, silver (Ag), and nitrogen (N) doped NaTaO3 photocatalysts have photocatalytic H2 evolution rates of 556 µmolh−1, 2834 µmolh−1 and 3266 µmolh−1, respectively. Without a co-catalyst, the maximal rate of H2 generation under UV light has not yet been attained for the N-doped NaTaO3 perovskite with its cubic (3-D) structure. Furthermore, even after three days, the improved photocatalyst demonstrates 87 % of photocatalytic activity in the reliability test.

Polyimide/Ag2WO4 Z-Scheme Heterojunction for Efficient Photocatalytic Degradation of Tetracycline.

It is of great significance to construct a Z-scheme heterojunction for improving solar light harvesting and achieving efficient separation of photogenerated carriers and then enhancement of the photocatalytic performance of semiconductor photocatalysts. Herein, the direct Z-scheme PI/Ag2WO4 heterojunction was designed and prepared according to the band edge potentials of the semiconductor. Due to the fact that the Z-scheme structure not only endowed the PI/Ag2WO4 composites with efficient separation of photogenerated electron-hole pairs but also reserved the redox ability of the valence band and conduction band of monophase catalysts, the 50% PI/Ag2WO4 heterojunction exhibited excellent photocatalytic activity, which were 2.9 and 1.5 times those of the PI and Ag2WO4 photocatalysts, respectively. The photocatalytic reaction mechanism of PI/Ag2WO4 composites was confirmed by the results of TEM, UV-vis, XPS, and EPR experiments. This work provides a feasible strategy to design high-performance photocatalysts in the field of practice purification of wastewater.

Effective prediction of SnO2 conduction band edge potential: The key role of surface oxygen vacancies.

Several theoretical studies at different levels of theory have attempted to calculate the absolute position of the SnO2 conduction band, whose knowledge is key for its effective application in optoelectronic devices such us, for example, perovskite solar cells. However, the predicted band edges fall outside the experimentally measured range. In this work, we introduce a computational scheme designed to calculate the conduction band minimum values of SnO2, yielding results aligned with experiments. Our analysis points out the fundamental role of encompassing surface oxygen vacancies to properly describe the electronic profile of this material. We explore the impact of both bridge and in-plane oxygen vacancy defects on the structural and electronic properties of SnO2, explaining from an atomistic perspective the experimental observables. The results underscore the importance of simulating both types of defects to accurately predict SnO2 features and provide new fundamental insights that can guide future studies concerning design and optimization of SnO2-based materials and functional interfaces.

Cu-doped CdS-TiO2 combined with upconverting particles for NIR-induced photocatalytic CO2 reduction

The influence of copper doping of cadmium sulfide on the activity in composites with TiO2 (anatase) for photocatalytic CO2 reduction was examined. CdS and (Cu,Cd)S were synthesized by the hydrothermal method and characterized using XRD, XPS, SEM, EDS, and XRF methods. It was found that copper doping is responsible for the shift of band edge potentials. The mechanisms of photocatalytic performance of the created heterojunctions were elucidated with photoelectrochemical, spectroelectrochemical and surface photovoltage techniques. The S-scheme heterojunction was recognized for both examined systems. The obtained composites were examined under Xe-lamp radiation in the gas phase revealing CO2 reduction to CO. Moreover, the photocatalytic performance under NIR irradiation was demonstrated with the use of the upconverting nanoparticles (UCPs) added to the photocatalytic system. It was found that Cu doping improved the photocatalytic performance of CdS/TiO2 in CO2 to CO conversion mainly through the increase of the photostability of the sulfide system.

Catalytic photo-degradation of brilliant green and bacterial disinfection of Escherichia coli by the action of Y2Ti2O7/AgO films

In this study, we evaluated the photocatalytic efficacy of pure Y2Ti2O7 films incorporating varying AgO ratios (1.0, 3.0, and 5.0 mol%) in the degradation process of brilliant green dye and in the bacterial disinfection of Escherichia coli under UV–visible illumination. The films were prepared utilizing a photochemical methodology involving β-diketonate complexes of Y(dbm)3, Ti(dbm)4, and Ag(acac) as starting materials. Following synthesis, the photo-deposits underwent calcination at 900 °C for 2 h and were subsequently analyzed using Fourier Transform Infrared Spectroscopy, X-Ray diffraction, Scanning Electron Microscopy - Energy Dispersive X-ray Spectroscopy, and X-ray Photoelectron Spectroscopy. The outcomes of these characterizations indicate the formation of a pyrochlore Y2Ti2O7 cubic phase, with the emergence of AgO in the doped samples. Photocatalytic performance yielded significant results, with a 94.9 % degradation of brilliant green observed for Y2Ti2O7 samples doped at 3.0 mol%, and a 98.4 % inhibition of Escherichia coli cultures observed for Y2Ti2O7 samples doped at 1.0 mol%. Theoretical calculations were employed to determine the band edge potentials of both oxides, supporting the establishment of a type I heterojunction between the Y2Ti2O7 phase and AgO. A degradation mechanism has been postulated based on assays involving the blocking of reactive oxygen species and charge carriers through the use of specific inhibitors.

Ab-initio study of strain-tunable g-GaN/BN nanoheterostructure for optoelectronic and photocatalytic applications.

Two-dimensional (2D) nanoheterostructures of materials, integrating various phase or materials into a single nanosheet have stimulated large-scale research interest for designing novel two dimensional devices. In contemporary analysis present work, we examined the structural and electronic properties of the isolated 2D BN and GaN monolayers. We have investigated the structural stability and optoelectronic and photocatalytic response of the g-GaN/BN nanoheterostructure along with its response to strain. Nanoheterostructure g-GaN/BN is predicted to be a direct bandgap semiconductor with wide gap of 4.45eV, whose value can be effectively modulated by applied strain ( , ranging from 4.55 ( = - 4%) to 3.58eV ( = 8%). We also discovered that the tensile strain of 8% can substantially tune the direct bandgap of nanoheterostructure to indirect band gap nature. Even more important, the biaxial tensile strain engineering accentuates an enhancement of optical absorption in the UV region, broadening the light harvesting of the g-GaN/BN nanoheterostructure with the shifting of first absorption peak from 4.64 ( = - 4%) to 3.71eV ( = 8%). Furthermore, strain-tuned band edge potentials arrangement perfectly fits the water reduction and oxidation redox potentials. Our findings portend that the g-GaN/BN nanoheterostructure has application in prospective nanoscale optoelectronic devices and photocatalytic hydrogen evolution system. First principles calculations in this study are performed using density functional theory. Generalized gradient approximation within PBEsol functional employed to address the electron-electron exchange-correlation effects. For avoiding periodic interactions between the layers, we have inserted a vacuum region of thickness 10Å in the z-direction. For ensuring the convergence accuracy of the computed results, convergence criteria of the iteration process is set to be 0.0001eV. Local modified Becke-Johnson, a semi local functional, is applied for calculating electronic and optical properties for more accuracy of results. As in layered 2D nanoheterostructure, a factual depiction of the van der Waals interactions cannot be provided by conventional DFT techniques. Accordingly, in order to incorporate these interactions, we had employed the dispersion correction method of Grimme's.

Tunable Interfacial Electronic and Photoexcited Carrier Dynamics of an S-Scheme MoSi2N4/SnS2 Heterojunction.

Exploring and designing an efficient S-scheme heterojunction photocatalyst for water splitting are crucial. Herein, we report the interfacial electronics, photoexcited carrier dynamics, and photocatalytic performance for water splitting of the MoSi2N4/SnS2 van der Waals heterojunction under the modulation of an electric field and biaxial strain. Our results show that the MoSi2N4/SnS2 heterojunction has a direct band gap of 0.41 eV and obeys the S-scheme charge transfer mechanism. Further calculations of the photoexcited carrier dynamics demonstrate that the interfacial carrier recombination time is 7.22 ps, which is shorter than the electron (hole) transfer time of 39.5 ps (566 ps). Moreover, under the effect of a positive electric field and tensile strain, the S-scheme MoSi2N4/SnS2 heterojunction exhibits excellent visible-light absorption, satisfactory band-edge potentials, tunable interfacial charge transfer, and spontaneous hydrogen evolution reaction activity. The calculated STH efficiency indicates that a tensile strain of 2% is the most effective means of improving the photocatalytic performance of the S-scheme MoSi2N4/SnS2 heterojunction.

Effect of silver doping on the band gap tuning of tungsten oxide thin films for optoelectronic applications

In the cutting-edge world, semiconductor metal oxides usually tend to have a high optical band gap (>3.0 eV), significantly acceptable for potential optoelectronic applications. The present study discusses the synthesize of pristine tungsten trioxide (WO3) and Silver (Ag) doped WO3 (Ag: WO3) thin films onto a glass substrate at 450 °C, with varying concentrations of Ag doping (2, 4, 6, 8 and 10 at.%) using a simple Spray Pyrolysis Technique. Field emission scanning electron microscopy (FESEM) analysis showed the presence of particles in the WO3 and Ag: WO3 materials. The X-ray diffraction (XRD) pattern confirmed that the samples' hexagonal structure remained intact. In addition, Rietveld refinement was used for the samples to study the crystal structure meticulously. Because of the surface plasmon resonance effect, the samples' distinguishing characteristics were visible in their optical nature. For pristine WO3, the experimental band gap was determined to be 3.20 eV, and for varying doping concentrations, it was found to be 3.15 eV–2.90 eV, respectively. Furthermore, the fracture has remained imperceptible at elevated concentrations, resulting in a substantial influence on the optical characteristics of 10% Ag: WO3 thin films. The estimated redox potential for 2% Ag: WO3 shows a considerable influence of the band edge potential of the Conduction Band (CB) and Valance Band (VB). The activation energy was determined using temperature-dependent electrical resistivity and exhibited an ohmic nature. The synthesized material exhibited a negative temperature coefficient (NTC) effect at higher concentrations of doping, suggesting its potential applicability as a thermistor. A comprehensive analysis of this present study indicates that Ag can be a viable candidate for doping on WO3 thin films for use in optoelectronic devices.

Two-Dimensional SiH/g-C3N4 van der Waals Type-II Heterojunction Photocatalyst: A New Effective and Promising Photocatalytic Material

The two-dimensional layered heterostructure have been demonstrated as an effective method for achieving efficient photocatalytic hydrogen production. In this work, we propose, for the first time, the creation of van der Waals heterostructures from monolayers of SiH and g-C3N4 using first-principle calculations. We also systematically investigated additional properties for the first time, such as the electronic structure and optical behavior of van der Waals heterostructures composed of SiH and g-C3N4 monolayers. The results of this study show that the SiH/g-C3N4 heterostructure is categorized as a type-II heterostructure, which has a bandgap of 2.268 eV. Furthermore, the SiH/g-C3N4 heterostructure interface was observed to efficiently separate and transfer photogenerated charges, resulting in an enhanced photocatalytic redox performance. Moreover, the calculation of HOMO (Highest occupied molecular orbital) and LUMO (Least unoccupied molecular orbital) and charge density difference can further confirm that the SiH/g-C3N4 heterojunction is a type-II heterojunction, which has excellent photocatalytic hydrogen production and water decomposition performance. In addition, the SiH/g-C3N4 heterostructure exhibited excellent HER (Hydrogen evolution reaction) efficiency. This is essential for the process of photocatalytic water splitting. In SiH/g-C3N4 heterojunctions, the redox potential required for water splitting is spanned by the band edge potential. Calculating the absorption spectra, it was discovered that the SiH/g-C3N4 heterostructure possesses outstanding optical properties within the visible-light range, implying its high efficiency in photocatalytic hydrogen production. This research provides a broader research direction for the investigation of novel efficient photocatalysts and offers effective theoretical guidance for future efficient photocatalysts.

Stabilizing the dopability of chalcogens in BaZrO3 through TiZr co-doping and its impact on the opto-electronic and photocatalytic properties: A meta-GGA level DFT study

Band structure engineering of large band gap perovskite oxides allows enhancing their optical absorption capabilities in the visible region of the electromagnetic spectrum which enables their use in green energy technologies harnessing solar radiations. Since introducing isovalent cation and anion co-dopants in ABO3 perovskite can facilitate tuning of their band gaps, in the present work we examine the synthesis feasibility of Ti and X (where X = S, Se and Te) dopants at zirconium and oxygen-sites, respectively, of BaZrO3 using first-principles density functional theory calculations. For an accurate determination of thermodynamic, structural and energetic properties of the pristine, mono-doped and TiZr + XO co-doped BaZrO3, we have employed semi-local SCAN meta-GGA functional. Moreover, the TB-mBJ meta-GGA potential functional was used to circumvent the band gap underestimation of the electronic and optical properties made by SCAN. Our results indicate that introducing TiZr as a co-dopant in XO-doped BaZrO3 not only improves the thermodynamics of introducing an chalcogen atom at oxygen-site under optimal chemical environment, it also allows tuning the band gap of cubic BaZrO3 for absorption of radiation in the visible spectrum. We also perform a side-by-side comparison of the photocatalytic water molecule dissociation efficiency of pristine, XO-doped, TiZr-doped and TiZr +XO co-doped BaZrO3 to examine their potential application in hydrogen evolution process. Based on our computed optical properties and band-edge potentials, we propose TiZr+TeO co-doped BaZrO3 as the best candidate for photocatalytic water molecule dissociation under solar irradiation.

Dual functionality of the BiN monolayer: unraveling its photocatalytic and piezocatalytic water splitting properties.

To achieve scalable and economically viable green hydrogen (H2) production, the photocatalytic and piezocatalytic processes are promising methods. The key to successful overall water splitting (OWS) for H2 production in these processes is using suitable semiconductor catalysts with appropriate band edge potentials, efficient optical absorption, higher mechanical flexibility, and piezoelectric coefficients. Thus, we explore the bismuth nitride (BiN) monolayer using density functional theory simulations, revealing intriguing catalytic properties. The BiN monolayer is a semiconductor with an indirect electronic bandgap (Eg) of 2.08 eV and displays excellent visible light absorption (approximately 105 cm-1). Detailed analyses show that the band edges satisfy the redox potential for photocatalytic OWS via biaxial strain engineering and pH variation. Notably, the solar to hydrogen conversion efficiency (ηSTH) for the BiN monolayer can reach 17.18%, which exceeds the 10% efficiency limit of photocatalysts for economical green H2 production. The obtained in-plane piezoelectric coefficient of e11 = 16.18 Å C m-1 is superior to widely studied 2D materials. Moreover, the generated piezopotential under oscillatory strain stands at 28.34 V, which can initiate the water redox reaction via the piezocatalytic mechanism. This originates from the mechanical flexibility coupled with higher piezoelectric coefficients. The result highlights the BiN monolayer's potential application in photocatalytic, piezocatalytic, and photo-piezo-catalytic OWS.