Band Positions Research Articles

A practical stability/instability chart analysis for slope large deformations using the material point method

Slope instability and failure may lead to severe geological disasters, which are a primary concern of geotechnical engineering. To estimate the safety of a slope, Taylor (1937) proposed a stability chart that evaluates the factor of safety (FOS) of a homogeneous slope using several simple geometric and material parameters. This study extends the stability chart further into the field of failure, summarising and discussing the failure mode and affected area. A few hundred slope failure simulations have been conducted using the material point method (MPM), which reproduces similar FOSs to traditional stability charts. Three major failure modes, i.e., face failure, toe failure, and base failure, are categorized according to the different positions of the failure bands, and a failure mode distribution spectrum chart is established according to the material parameters of the slope. The affected area of slope failure is characterized by four indicators: the influence distance, run-out distance, sliding depth, and sliding volume. An instability chart is proposed to describe the affected area of slope failure based on simple geometry and material parameters. Further analysis indicates that the internal friction angle plays the most prominent role in the failure modes and slope failure volumes.

Selective removal of single-layer graphene over double-layer graphene on SiO2 by remote oxygen plasma irradiation

Graphene sheet transferred onto the SiO2 substrate has various types at different regions such as single-layer graphene (SLG), double-layer graphene (DLG), and multi-layer graphene (MLG). These layers were identified by Raman analysis of 2D band position around 2700 cm−1 and full width at half maximum (FWHM). The transferred graphene sheets on SiO2 were remotely irradiated by oxygen plasma without energetic ions at a room temperature. At the beginning of the oxygen plasma irradiation, the carbons on the surface of the graphene sheets were oxidized and the 2D-FWHMs were broadened due to an increase of defects on the basal plane. By controlling the plasma irradiation time up to 120 min, selectively stripping away the SLG regions on the SiO2 surface was observed while leaving the other DLG and MLG regions. The difference in attractive forces resulted in favorable desorption of carbon atoms occurred in the oxidized SLG regions on SiO2 surface by the remote oxygen plasma irradiation.

SEM/Raman spectroscopy of clathrites as analogs of authigenic carbonates in ocean worlds

AbstractThere is evidence from the near‐infrared observations of space missions of the presence of carbonates on the surface of several ocean worlds. However, their genesis remains unresolved. We investigate the hypothesis that these carbonates may be in the form of clathrites assuming that clathrate hydrates are stable phases in the crust and ocean of these ocean worlds. In order to support this, we studied a sample of a potential clathrite from the Hydrate Ridge cold seep (Cascadia Subduction Zone), the carbonate rock fossil of clathrate hydrates, as a terrestrial analogue. We characterised the mineralogy and texture of the sample by using a coupled confocal Raman microscope and scanning electron microscopy instrument with the aim of identifying possible geo‐ and biosignatures, which could be relevant for future missions of exploration to ocean worlds and Mars. Our results show that aragonite is the dominant mineral phase in the clathrite sample, but Mg‐calcite and dolomite were also identified. These three carbonates constitute a pattern related to clathrate hydrate formation and dissociation processes. Dolomite was defined as a biosignature of gas hydrate microbiomes because it was integrated within Mg‐calcite grains precipitated after clathrate hydrate dissociation. Nevertheless, no spectral changes were observed in Raman bands of carbonate minerals that would indicate the influence of clathrate hydrates in their genesis. We also observed that Raman band positions of the associated framboidal pyrites are a characteristic signature of the associated framboid‐like texture because its potential as biosignature may only be attributed by biochemical analysis.

Monolayer BiOI doped with nonmetals (B, C, N, Si, P, S) to enhance photocatalytic hydrogen precipitation performance

Efficient photocatalysts play a crucial role in producing green and clean hydrogen energy. BiOI is a good material for photocatalytic hydrogen generation. However, the low position of the conduction band also affects its redox ability. We studied the electronic structure and hydrogen evolution reaction (HER) catalytic performance of six nonmetals doped BiOI based on the first principles calculation. The relationship between doping elements and catalytic performance was explained. We used the DFT + U method to find that the band gap values of X-BiOI (X = B, C, N, Si, P, S) are 1.99 eV, 1.23 eV, 1.73 eV, 2.08 eV, 1.40 eV and 1.77 eV, respectively. After nonmetal doping, the bottom position of the conduction band of BiOI rises, which enhances the reduction ability. Specifically, the impurity energy levels generated in the band gap of B and Si doped BiOI reduce the recombination rate of photogenerated carriers, and lower the work function to 5.62 eV and 5.45 eV, respectively. Studies on hydrogen production performance show that B-doped BiOI has the strongest reduction ability and the best catalytic effect, with the lowest ΔGH* (1.57 eV). This research provides some ideas for understanding nonmetal doped materials for the photocatalytic hydrogen evolution system.

Effect of Metal d Band Position on Anion Redox in Alkali-Rich Sulfides.

New energy storage methods are emerging to increase the energy density of state-of-the-art battery systems beyond conventional intercalation electrode materials. For instance, employing anion redox can yield higher capacities compared with transition metal redox alone. Anion redox in sulfides has been recognized since the early days of rechargeable battery research. Here, we study the effect of d-p overlap in controlling anion redox by shifting the metal d band position relative to the S p band. We aim to determine the effect of shifting the d band position on the electronic structure and, ultimately, on charge compensation. Two isostructural sulfides LiNaFeS2 and LiNaCoS2 are directly compared to the hypothesis that the Co material should yield more covalent metal-anion bonds. LiNaCoS2 exhibits a multielectron capacity of ≥1.7 electrons per formula unit, but despite the lowered Co d band, the voltage of anion redox is close to that of LiNaFeS2. Interestingly, the material suffers from rapid capacity fade. Through a combination of solid-state nuclear magnetic resonance spectroscopy, Co and S X-ray absorption spectroscopy, X-ray diffraction, and partial density of states calculations, we demonstrate that oxidation of S nonbonding p states to S2 2- occurs in early states of charge, which leads to an irreversible phase transition. We conclude that the lower energy of Co d bands increases their overlap with S p bands while maintaining S nonbonding p states at the same higher energy level, thus causing no alteration in the oxidation potential. Further, the higher crystal field stabilization energy for octahedral coordination over tetrahedral coordination is proposed to cause the irreversible phase transition in LiNaCoS2.

Optical characterization and thermal analysis of rare earth-doped PbO-GeO2-Ga2O3 glasses embedded with gold nanoparticles

This study investigated the optical properties of PbO-GeO2-Ga2O3 glasses doped with Er3+ and Yb3+ rare earth ions, deposited with gold nanoparticles and annealed at different times (1 h, 12 h, 28 h, and 52 h). By varying the annealing times, we can understand how these thermal processes influence the position of the energy bands, which in turn affects the material’s optical properties such as the energy gap and Urbach energy. The study found that the sample annealed for 52 h had the lowest Eg value and the highest Eu value, indicating significant structural changes due to prolonged thermal treatment. The study aimed to determine the energy gap (Eg) and Urbach energy (EU), Judd-Ofelt parameters (Ω2, Ω4, Ω6), oscillator strength (fexp and fcal), and root mean square (RMS) deviation. Additionally, the study reports on the linear absorption and heat transfer results, which were used to evaluate temperature changes during Z-scan experiments. The data obtained indicate that the sample subjected to 52-hour annealing has the smallest Eg value, suggesting that intense thermal processes and crystallisation affect the positions of the material’s energy bands, increasing its ability to absorb light. Consequently, the EU value for this sample is the highest at 0.312 eV, decreasing to 0.203 eV for the sample annealed for 1 h. This indicates that longer annealing times result in more significant structural changes in the glass matrix, thereby modifying its optical properties. The analysis of the obtained results, leads to the conclusion that the lowest values of both experimental (fexp) and calculated (fcal) oscillator strength occur at 546 nm and 811 nm, indicating the potential energy properties of the 4S3∕2 and 4I9∕2 levels in the atomic structure. It was observed that the J-O parameters did not exhibit significant changes with increased annealing time, suggesting that short-term thermal processes may be sufficient to achieve a stable energy configuration. This finding is of significant practical importance, as it indicates that the material can maintain its optical properties even with shorter annealing times, thereby enhancing the efficiency of the production process.

Anchored MoS2 co-catalysts on ZnxCd1-xS solid solution for photocatalytic reduction of U(VI)

In recent years, a great deal of attention has focused on achieving higher photocatalytic performance by modifications. However, external modification methods, such as heterojunction, defect engineering and doping, bring the disadvantage of mismatch of energy band positions or uncontrollable defects and doping positions, resulting in different photocatalytic efficiencies for different batches of materials. As a result, the search for new modification methods is currently the focus of photocatalytic reduction of U(VI). In this work, the modification method of forming a solid solution between Zn, Cd and S by adjusting the ratio of Zn /Cd precursors, i.e., the internal modification method, is proposed to solve the problem of matching the energy band structure, keeping the conduction band in the right position and facilitating efficient charge separation, and complexing with MoS2 co-catalysts to improve the catalytic performance of the catalyst. A novel complex, MoS2/Zn0.2Cd0.8S, has been designed and synthesized. And the photocatalytic reduction of U(VI) by Zn0.2Cd0.8S was 27 and 373 times higher than that of pure CdS and ZnS, respectively, and MoS2/Zn0.2Cd0.8S was 24.45 % higher than that of Zn0.2Cd0.8S (74.75 %), with a reduction rate of 99.20 % under 60 min of illumination. Gladly, its photocatalytic activity remained above 95.67 % after five cycles, and there was no difference in the performance of catalysts synthesised in different batches, showing excellent stability and reproducibility. Moreover, the mechanism of U(VI) reduction was investigated by MoS2/Zn0.2Cd0.8S. This study provides a new strategy to guarantee the preparation of photocatalysis with stable performance and improve photocatalytic performance.

Elucidation of the optical, electronic, and photoelectrochemical properties of p-type CuFe2O4 photocathodes

High-quality thin films of p-type CuFe2O4 photocathode were prepared for the first time on FTO-coated glass substrates by a novel nonaqueous solution using spray pyrolysis method. The films' critical physical and photophysical properties, including morphology, optical properties, carrier transport properties, band position, and photoelectrochemical (PEC) characteristics, were analyzed and estimated. The feasibility of PEC water splitting was systematically evaluated. The prepared reddish-brown CuFe2O4 film exhibits a compact and uniform morphology. Its optical bandgap is approximately 1.42 eV, and it possesses a suitable conduction band position, indicating its capability to facilitate solar-driven water splitting and absorb visible light. Under AM 1.5 simulated solar illumination, the photocurrent density of 12 μA/cm2 was attained in a 1 mol NaOH solution. However, the prepared CuFe2O4 films demonstrate instability under constant light in the electrolyte owing to the copper reduction reaction. These research results offer a fresh insight into the potential application of CuFe2O4 as a photocathode semiconductor in PEC water splitting.

Effect of Al Substitution on Visible Short-Wave Infrared Reflectance Spectroscopy (VSWIR) of Goethite and Ferrihydrite

Goethite and ferrihydrite are the two major iron hydroxides, essential mineral constituents in the terrestrial surface system. Aluminum (Al) is the most common substituent in iron hydroxides, and it may significantly change the bulk and surficial physicochemical properties of iron hydroxides. Consequently, a practical and convenient approach is needed to efficiently identify the Al substitution degrees of iron hydroxides in natural occurrences. This study presents a comprehensive investigation of the VSWIR characteristics of laboratory-synthesized Al-substituted goethite and ferrihydrite, to establish diagnostic VSWIR parameters for the identification and quantification of Al substitution levels in iron hydroxides. The findings revealed that Al substitution can affect the band positions (P) of goethite and ferrihydrite at ~650 nm, ~900 nm, and ~1400 nm. The relationships between the Al substitution of ferrihydrite and VSWIR parameters can be expressed as P900 = −0.43 × Al(%) + 931 and P1400 = −0.07 × Al(%) + 1428, while that of goethite can be expressed as P650 = 0.42 × Al(%) + 657 and P900 = 2.29 × Al(%) + 936. The peak fitting results showed that the absorption intensity at 480–550 nm linearly decreases with increased Al substitution. The obtained VSWIR spectra of Al-substituted goethite and ferrihydrite provide a critical supplement to the spectral library for (Al) iron hydroxides, and these VSWIR parameters can be utilized for the semi-quantitative determination of Al substitution in natural iron hydroxides

Controlled humidity synthesis of surface sulfate functionalized CdS for enhanced visible light photocatalysis

At present, the pollution of antibiotic wastewater is serious, which has a potential impact on the survival of organisms. In this study, SO42- functionalized small-sized flower-like CdS is successfully synthesized by utilizing H2S at various levels of relative humidity. The CdS catalyst is then employed for the degradation of tetracycline hydrochloride (TC) through photocatalytic processes. Experimental findings indicate that CdS-8 %RH exhibits the highest photocatalytic efficiency, degrading 98.6 % of TC within 80 min, which is 1.5 times more efficient than CdS alone. HPLC-MS analysis is used to identify degradation intermediates and pathways, and to evaluate the toxicity and mutagenicity of these intermediates. The photocatalytic mechanism is elucidated through species capture experiments, electrochemical tests, KPFM tests, and conduction valence band position analysis.

Micro-FTIR reflectance spectroscopy of Ryugu, CI chondrites and volatile-rich clasts – Comparing spectral features in the Mid-IR (2.5–16.5 μm) region

Although C1 clasts in carbonaceous chondrites are usually mineralogically similar to CI chondrites, they often exhibit distinct chemical or isotope characteristics, indicating that the diversity of carbonaceous matter is larger than represented by currently known meteorites. Samples returned by the Hayabusa2 mission provide an excellent opportunity to directly compare remote sensing data with laboratory spectra and elaborate on meteorite-asteroid links.We obtained reflectance spectra from 10 carbonaceous samples of extraterrestrial origin to identify spectral differences in the wavelength region between 2.5 and 16.5 μm. We investigated seven volatile-rich clasts, two CI chondrites, and a fragment from the asteroid Ryugu, recently returned by the Hayabusa2 mission. To obtain representative spectra from a lithology, we performed multiple analysis with an aperture size of 100 μm × 100 μm. Subsequently, spectral features were correlated with petrographic and chemical data.The phyllosilicate composition of the investigated C1 and C2 clasts is on average more Fe-rich compared to bulk CI chondrites, which is spectrally reflected in lower Christiansen feature (CF)/Reststrahlenband (RB) ratios. Our results confirm previous studies that indicate that the band area of the OH absorption band at 2.7 μm is dependent on the phyllosilicate composition. A high Mg abundance in phyllosilicates leads to a stronger OH absorption band. Varying degrees of aqueous alteration cause mineralogic differences that are observable in the reflectance spectra. Either in form of a band center shift towards smaller or longer wavelengths, depending on the metal cation giving rise to the M-OH absorption band, and/or a generally weaker OH absorption band, and a broad Reststrahlen band (RB) at 10 μm, with two minor RBs emerging at 11.3 and 12 μm. In contrast, most C1 clasts show a single RB at ≈10 μm, and a constant OH band position at 2.70 μm. The abundance of minor constituents, such as sulfides and carbonates, can also affect the spectrum. Dolomite produces two diagnostic bands at 6.5 and 11.3 μm, whereas pyrrhotite, devoid of diagnostic bands in this wavelength region, increases the background while decreasing the RB intensity.Our findings indicate that within a laboratory framework, subtle mineralogic differences among hydrated carbonaceous materials can be spectroscopically detected. The spectra of Ryugu sample A0008 show a distinctive OH absorption band, as seen in the globally retrieved data by the NIRS3 instrument for Ryugu (Kitazato et al., 2019). Under specific circumstances, micro-FTIR reflectance spectra can be qualitatively compared to remote sensing spectra, and help to further elaborate on meteorite-asteroid links.

Variable Doppler Starting Point Keystone Transform for Radar Maneuvering Target Detection

The Doppler band compensated by the keystone transform (KT) is limited. Therefore, it needs to be used in conjunction with the Doppler ambiguity compensation function to correct the range migration (RM) caused by maneuvering targets with Doppler ambiguity. However, the KT implemented by sinc interpolation suffers from significant performance loss at boundaries of compensation Doppler bands. Additionally, in a multi-target scenario, KT implementation methods occupy high complexity when the Doppler range of targets spans over two compensation Doppler bands. To address the aforementioned issues, this study presents a variable Doppler starting point keystone transform (VDSPKT) method, where a new form of ambiguity compensation function is constructed, turning the Doppler starting point of the compensation band in KT variable. Firstly, the position of the compensation Doppler band is changed from fixed to adjustable as needed, enhancing the flexibility of KT. Crucially, the connection points of the compensation Doppler bands in sinc interpolation are reset, avoiding performance loss at their boundaries. Also, the compensation band is adjusted to cover the narrow Doppler frequency range caused by targets, significantly improving computational efficiency. Finally, the simulation and real data experiments demonstrate that the proposed approach effectively addresses the performance degradation and high computational complexity of KT in the aforementioned scenarios, resulting in a computational load reduced by approximately 50% compared to traditional methods.

In Situ Electrochemical Cobalt Doping in Perovskite-Structured Lanthanum Nickelate Thin Film Toward Energy Conversion Enhancement of Polymer Solar Cells.

This study demonstrates that the electrochemical doping of lanthanum nickelate (LNO) with cobalt ions is a promising strategy for enhancing its physical and electrochemical properties, which are critical for energy storage and conversion devices. LNO emerges as a promising hole transport layer (HTL) in solar cells due to its stability, large band gap, and high transparency. Nevertheless, its low conductivity and improperly aligned band positions are persistent problems. Here, in a pioneering endeavor, Co-doped LNO thin films were synthesized electrochemically and applied as the HTL in polymer solar cells (PSCs). Characterization revealed the impact of Co doping on the electrochemical, structural, morphological, and optical properties of LNO thin films. Depending on the Co doping level, PSCs based on 10 mol % Co-doped LNO outperformed pure LNO, achieving a champion efficiency of 6.11% with enhanced short-circuit current density (12.84 mA cm-2), fill factor (68%), open-circuit voltage (0.70 V), and external quantum efficiency (82.6%). This enhancement resulted from decreased series resistance, refined surface morphology, minimized trap-assisted recombination, enhanced conductivity, increased charge carrier production, favorable energy level alignment, and improved current extraction facilitated by LNC0.10O HTL. Moreover, the unencapsulated PSC-LNC0.10O long-term stability notably improved and retained 86% of its initial PCE after 450 h storage in ambient air, 82% after being continuously heated to 85 °C for 300 h, and 80% after operating at maximum power point for 300 h. These findings offer a straightforward approach to enhancing PSC performance through Co doping of LNO, supported by density functional theory (DFT) calculations that validate the experimental results and confirm the improvement in optical properties and stability of PSCs as an HTL.

Spectrophotometric adsorption isotherms of paraquat and methylene blue on montmorillonite: Unveiling adsorption modes without filtration or centrifugation

Measuring adsorption isotherms in a single experimental run is important for designing environmentally friendly adsorption experiments, reducing resources usage and contamination risks. In this study, one-pot adsorption isotherms of the divalent cation paraquat (PQ) and the monovalent cation methylene blue (MB) on montmorillonite were directly measured by UV-Vis spectrophotometry, with no need for separation of the solid phase from the aqueous phase by filtration or centrifugation. PQ adsorption resulted in a bathochromic shift (red shift) in the absorption band position, moving from 258 nm to 277 nm, and only one adsorbed species was detected. MB adsorption induced a hypsochromic shift (blue shift) from 664 nm to lower wavelengths, and at least three different adsorbed species were identified. In the case of PQ, the spectrophotometric isotherm coincided with a regular isotherm, saturating at the cation exchange capacity (CEC) of the solid, 9.1×10−4 Eq/g. In the case of MB, the spectrophotometric isotherm also saturated at the CEC, but the regular isotherm saturated at a higher adsorption extent, 1.2×10−3 Eq/g. In both cases, the presence of negative structural charges of the clay and the planar environment of the interlayer space were crucial for inducing the observed spectral changes. PQ neutralizes the charges of montmorillonite adsorbing as a monomer and undergoing rigidification and planarization in the clay interlayer. On the contrary, MB is forced to form dimers to accomplish the same charge neutralization.

Mechanisms of formation of heteroassociates of ATP with ag+ ions

Emission and excitation spectra of fluorescence (FL) were studied for aqueous solutions of ATP with AgNO3 salt at different concentrations of silver nitride and temperatures. It is shown that with increasing Ag+ content and temperature, a complex nature of FL quenching occurs due to the formation of ATP - Ag+ complexes. This quenching occurs when the position of the emission bands and FL excitation of the ATP fluorophore is preserved, and the quenching corresponds to the Stern-Volmer linear dependence. At the same time, the values of KSV and kq and their dependence on the temperature indicate a static quenching mechanism. The binding parameter n indicates that the metal–ligand complexes have a stoichiometric ratio of 1:1, and KA decreases with increasing temperature. In the heteroassociates, energy is transferred by the FRET mechanism, and binding of components is mainly realized due to electrostatic and van der Waals interaction.

Recent Advances in Metal Oxide Electron Transport Layers for Enhancing the Performance of Perovskite Solar Cells.

Perovskite solar cells (PSCs) have attracted considerable interest owing to their low processing costs and high efficiency. A crucial component of these devices is the electron transport layer (ETL), which plays a key role in extracting and transmitting light-induced electrons, modifying interfaces, and adjusting surface energy levels. This minimizes charge recombination in PSCs, a critical factor in their performance. Among the various ETL materials, titanium dioxide (TiO2) and tin dioxide (SnO2) stand out due to their excellent electron mobility, suitable band alignment, high transparency, and stability. TiO2 is widely used because of its appropriate conduction band position, easy fabrication, and favorable charge extraction properties. SnO2, on the other hand, offers higher electron mobility, better stability under UV illumination, and lower processing temperatures, making it a promising alternative. This paper summarizes the latest advancements in the research of electron transport materials, including material selection and a discussion of electron collection. Additionally, it examines doping techniques that enhance electron mobility and surface modification technologies that improve interface quality and reduce recombination. The impact of these parameters on the performance and passivation behavior of PSCs is also examined. Technological advancements in the ETL, especially those involving TiO2 and SnO2, are currently a prominent research direction for achieving high-efficiency PSCs. This review covers the current state and future directions in ETL research for PSCs, highlighting the crucial role of TiO2 and SnO2 in enhancing device performance.

Probing the mesophase formation in thermotropic liquid crystal HBDBA using temperature-dependent Raman spectroscopy and DFT method

Liquid crystalline properties of the synthesized liquid crystal (LC) N-(o-hydroxybenzylidene)-N′-(4-n-alkoxybenzylidene) azines (HBDBA) are probed thoroughly using the comprehensive array of techniques e.g. differential scanning calorimetry (DSC), differential thermal analysis (DTA), polarizing optical microscopy (POM), temperature-dependent Raman spectroscopy and density functional theory (DFT) method. In this study, intricate molecular interactions crucial for mesophase formation of liquid crystalline system HBDBA and molecular rearrangement that occurs during LC transitions are unravelled comprehensively. Remarkably, at the Cr → SmA phase transition, the peak position, linewidth, and intensity of signature Raman bands are prominently changed. A thorough analysis of Raman marker bands and DFT calculation confirm the disruption of intramolecular hydrogen bonds in HBDBA at the Cr → SmA transition. The conclusion of the present study enriches the understanding of the underlying mechanisms of mesophase formation and intricate molecular interactions and arrangement at the molecular level of the thermotropic LC.

Low-frequency broadband valley transport for acoustic topology based on extended resonance

This paper proposes an extended resonant structure to solve the problem that topological acoustic waveguides have a narrow bandwidth at low frequencies. This acoustic structure consists of a two-dimensional structure and a resonant cavity in the three-dimensional direction, and its essence is to extend the resonant cavity in the two-dimensional structure to the three-dimensional direction. The problem that the size of the resonant cavity is limited by the size of the two-dimensional structure can be solved by this special extension. At the same time, the resonant cavity can be maximized in the three-dimensional direction. The topological properties of the original structure are not affected as long as the radius of the resonant cavity is widened without changing the symmetry of the overall composite structure. The rotating scatterer remains a reliable method for realizing topological phase transitions. The effect of the resonant cavity length on the band position is obtained using the finite element method, and it is demonstrated that the topological acoustic waveguide has a wide operating band at low frequencies. Simulation results show that this structure still has a bandgap width of 100 Hz at a low frequency of 350 Hz. The topological acoustic waveguide structure proposed in this paper can provide a new idea for the study of low-frequency broadband acoustic topology, which promotes the control of low-frequency acoustic waves by the topological acoustic waveguide.

Coproduction of hydrogen peroxide and formic acid as potential hydrogen-carrier through photocatalytic reformation of sacrificial chemical

This study explores the challenges to photo-reforming sacrificial chemicals into beneficial by-products while improving photocatalytic activity in H2O2 production by addressing several issues. The resorcinol-formaldehyde/graphitic carbon nitride composite (RF0.2GCN) with nanosheet-like RF morphology achieved a higher degree of surface-to-surface contact through -C-NH-CH2- and -NH-CH-OH than the nanosphere (RF0.8GCN). The RF0.2GCN produced H2O2 at 325.2 µg g−1 s−1 in the presence of oxalic acid (OA) at pH 2.1 with apparent quantum yield (AQY) of 12.7 %. The conduction band position potential was +0.54 VNHE, which is thermodynamically unfavorable for H+/H2 (E°: 0.00 VNHE) and O2/·O2- (E°: −0.046 VNHE) reaction and also inhibits the decomposition of H2O2 (H2O2/·OH, E°: +0.39 VNHE). Furthermore, the decomposition of OA formed formic acid (FA) at 82 % selectivity and concurrent CO2·- formation could promote electron density in the conduction band via its electron-donating ability·H2O2 was purified by isolating FA using anion exchange resin, and FA was recovered by desorption from the resin using HCl (pH 3).

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.