High Visible Light Absorption Research Articles

Mesoporous TiO2 enhanced by anchoring Mn3O4 for highly efficient photocatalyst toward photo-oxidation of ciprofloxacin

We describe the synthesis of mesoporous Mn3O4/TiO2 nanocomposites in the occurrence soft template. TEM images exhibited the Mn3O4/TiO2 nanocomposites homogeneous morphology with a particle size of ∼10–15 nm with close contact between TiO2 anatase and Mn3O4 crystals. The mesoporous Mn3O4/TiO2 nanocomposites were assessed toward degradation of ciprofloxacin (CIP) under visible illumination, which achieved 98.6% CIP degradation within 120 min. The degradation efficiency over porous 3% Mn3O4/TiO2 was greater 18 fold than that bare TiO2. The apparent degradation rate of the optimum 3% Mn3O4/TiO2 photocatalyst was fostered 22 folds higher than that of bare TiO2 NPs. Interestingly, the enhanced photocatalytic ability for Mn3O4/TiO2 heterojunction was significantly referred to the high absorption of visible light, synergistic effect and the unique structure with large surface area, which improved the CIP adsorption on porous Mn3O4/TiO2. Besides, the Mn3O4/TiO2 photocatalysts displayed stability and recyclability toward degradation of CIP for 10 h illumination. The photoelectrochemical and photoluminescence measurements of Mn3O4/TiO2 nanocomposites revealed an enhanced light-harvesting and effective electron-holes separation compared with bare TiO2. The prospective mechanism for degradation of CIP over Mn3O4/TiO2 heterojunction was presented.

First-principles study of the crystal structure, electronic and optical properties of Cu2O1-xMx (M = S, Se, Te)

Cu2O has the advantages of low price, stable chemical properties, and high visible light absorption rate. It is a very promising hole transport material in solar cells. However, the pure phase Cu2O has a low hole transport rate, which can be improved it by means of doping or something else. In this paper, based on the first-principles, the performance of different amounts of S, Se, and Te doped Cu2O are calculated, it is found that the Te-doped Cu2O performance is pronounced, with the energy gap reduction (1.871 eV), there appear free electron generating, the valence band maximum enables energy level is matched (−5.463 eV), and the absorption coefficient in the ultraviolet and visible range improved, nearly 103.07% at 3.26 eV, the reflectance increased to, for the point 11.7 eV, 76%, and the loss function value is very small in the visible light region (less than 0.1).

Z-Scheme Heterojunction of 3-Dimensional Hierarchical Bi3O4Cl/Bi5O7I for a Significant Enhancement in the Photocatalytic Degradation of Organic Pollutants (RhB and BPA).

In this study, we report the synthesis of a 3-dimensional (3D) hierarchical Bi3O4Cl/Bi5O7I (BOC/BOI) heterostructure for the photocatalytic degradation of Rhodamine-B (RhB) dye and colorless Bisphenol-A (BPA) pollutant under visible light. The heterostructure was prepared using in situ solvothermal and calcination methods. BOC/BOI exhibits a 3D hierarchical structure constructed with thin nano-platelets. The photocatalytic performance of the BOC/BOI photocatalyst demonstrated that the degradation efficiencies of RhB and BPA were 97% and 92% after light illumination within 90 and 30 min, respectively. In comparison, bare BOC and BOI efficiencies were only 20% and 10% for RhB dye, respectively, and 2.3% and 37% for BPA aqueous pollutants, respectively. Moreover, radical trapping measurements indicated that •O2− and •OH radicals played prominent roles in RhB and BPA degradation into mineralization. Analysis of band structures and photochemical redox reactions of BOC/BOI revealed a Z-scheme charge transfer between BOC and BOI by an internal electric field formed at the interface. Therefore, the highly improved photocatalytic performance of the BOC/BOI heterostructure is attributed to the synergetic effects of large surface area, high visible-light absorption, and the enhanced separation and transport of photo-excited electron–hole pairs induced by the hierarchical and Z-scheme heterojunction of the BOC/BOI.

Synergistic S-Scheme mechanism insights of g-C3N4 and rGO combined ZnO-Ag heterostructure nanocomposite for efficient photocatalytic and anticancer activities

The g-C3N4/rGO/ZnO-Ag (GCRZA) composite photocatalyst (PC) prepared by the facile hydrothermal method was effectively studied. The structural, morphological and optical, properties of as-synthesized materials were characterized by various characterization techniques. Photocatalytic activity of the as-prepared composite was examined using rhodamine B and methylene blue mixed (RhB+MB) aqueous dye under UV–visible light irradiation for 100 min. The GCRZA composite displayed a better photocatalytic performance against MB dye (90.04%) and RhB dye (83.45%) degradation performance. Moreover, the GCRZA composite PCs exhibited higher photocatalytic activity than pristine g-C3N4. The ultimate photocatalytic property was attained by implementating of g-C3N4/rGO in ZnO-Ag heterostructure, which could effectively decrease the optical bandgap and high visible-light absorption ability with suppressed e−/h+ recombination rate. After the five consecutive photocatalytic recycles, the GCRZA composite PC showed good stability without structural changes. Furthermore, the IC50 values showed that GCRZA nanocomposite (NC) has a higher cytotoxicity effect than g-C3N4/ZnO-Ag, g-C3N4/rGO and g-C3N4 against both HeLa and MCF-7 cell lines. As a result, this combination of nanocomposite has proven to exhibit higher photocatalytic and anticancer activity. Eventually, it may prove to be an effective tool for eradicating dye pollution from wastewater, and a way to prevent cancer mediated diseases in the cosmetics and pharmaceutical industries.

Photo-electrochemical and ozonation process to degrade ciprofloxacin in synthetic municipal wastewater, using C, N-codoped TiO2 with high visible-light absorption

Carbon, nitrogen-codoped TiO2 nanoroughness surfaces (CN-TiNRS) are successfully synthesized through electrochemical anodization at 50, 70 and 90 V (50 V-CN-TiNRS, 70 V-CN-TiNRS, and 90 V-CN-TiNRS, respectively), with the aim of shifting their absorption capacities to the visible-light region. The analysis by X-ray diffraction (XRD) and scanning electron microscopy (SEM) indicate that a TiO2 film with a major proportion of crystalline anatase and nanoroughness morphology is formed on the entire surface of all photoelectrodes. Carbon and nitrogen elements are detected by X-ray photoelectron spectroscopy (XPS) analysis for all samples, obtaining similar weight percentages. The best photoelectrochemical performance is reached for the 70 V-CN-TiNRS electrode subjected to Xe lamp radiation. Accordingly, this photocatalyst is chosen to perform all the ciprofloxacin (CIP) degradation tests in distilled water, involving the following methods: photocatalysis (PC), photoelectrocatalysis (PEC), Ozone (O3), photocatalytic ozonation (PCO) and photoelectrocatalytic ozonation (PECO). Degradation tests are additionally conducted in synthetic municipal wastewater (SWW) using PECO, to analyze its oxidation capacity in a real scenario (i.e. organic composition matrix). All techniques revealed that the highest CIP removal occurs with PECO, decreasing TOC by almost 86.79% (95% degradation by HPLC) after 90 min of treatment, thus, exploiting the intrinsic advantages of single PEC and O3. The radical trapping technique reveals that superoxide radicals (O2-•), holes (h+) and hydroxyl radicals (OH•) are responsible of the CIP abatement in the PECO. Reaction mechanisms are proposed for the production of these oxidants, while the CIP degradation pathway is rationalized using HPLC experiments. A toxicity test of the treated water is carried out after the process with PECO by means of germination with sativa lettuce seeds.

Facile synthesis of a novel photocatalyst with integrated features for industrial effluents treatment

Faster charge transport, excellent charge separation, narrow bandgap energy, lower electron-hole pair recombination rate, and high visible light absorption are the key features of an ideal photocatalyst material. Undoubtedly, semiconductor-based photocatalysts having remarkable charge separation efficiency have attracted considerable attention for degrading hazardous organic pollutants from contaminated water. So herein, a novel composite of reduced graphene oxide (rGO) supported by gadolinium doped bismuth yttrium oxide (Gd-BiYO3/rGO) was prepared by simple precipitation and ultrasonication method. The photocatalytic efficiency of the Gd-BiYO3/rGO composite was examined comparatively with pure BiYO3 and Gd-BiYO3 samples to degrade Methylene Blue (MB) dye under visible light irradiation. The Gd doping and rGO incorporation into BiYO3 increased the conductivity, improved the charge transfer efficiency, and impeded the charge recombination, resulting in superior photocatalytic activity of Gd-BiYO3/rGO. The kinetic studies exhibited the 96.2%, 61.5%, and 48.3% degradation of MB after 80 min irradiation of 1 SUN visible light under Gd-BiYO3/rGO, Gd-BiYO3, and BiYO3, respectively. The Gd-BiYO3/rGO composite degraded the MB dye at a rate (k = 0.0328 min-1) that is 5.05 and 2.68-fold higher than pure BiYO3 and Gd-BiYO3, correspondingly. The transient photocurrent response of Gd-BiYO3/rGO was comparatively 4.7 and 2.8 times greater than that of BiYO3 and Gd-BiYO3 photocatalysts, respectively. The dominant photocatalytic performance of Gd-BiYO3/rGO is primarily ascribed to the formation of heterojunctions between rGO nanosheets and Gd-BiYO3, which facilitate higher visible light absorbance, effective charge separation, and transfer through interfacial layers, more dye adsorption, lower charge transfer resistance, and hamper electron-hole pair recombination. Overall, the electrochemical results suggest that the current study provides an effective way to synthesize a heterostructure photocatalyst for removing organic pollutants from industrial effluents.

W:BiVO4-WO3-V2O5 heterostructures increase light absorption and charge transport in photoanodes for water splitting

Efficient light absorption and charge separation and transfer are the main obstacles that still need to be addressed to increase the performance of photoanodes for the water oxidation reaction. Here, we show that the combination of W:BiVO4, WO3, and V2O5 can simultaneously improve light absorption and the separation and transport of electrons and holes in the photoanode and consequently its photoelectrochemical performance for the water oxidation reaction. The high photoelectrochemical activity of the photoanode is due to the different bandgap energies of W:BiVO4 (2.44 eV), WO3 (2.90 eV), and V2O5 (2.27 eV), which provide higher absorption of visible light and improved charge transport in the heterojunction: V2O5 facilitates the transport of holes while WO3 increases electron mobility. As a result, the W:BiVO4-WO3-V2O5 photoanode produces a photocurrent density as high as 8.2 mA cm−2 at 1.23 V vs. RHE in sodium sulfate electrolyte (pH 6.96). By modifying the surface of the W:BiVO4-WO3-V2O5 photoanode with an electrocatalyst for water oxidation, the photocurrent can reach 12.1 mA cm−2. Thus, the multiple ternary heterojunctions of W:BiVO4-WO3-V2O5 proved an efficient strategy for producing high-performance photoanodes for photoelectrochemical applications.

High-performance and high-stability LaVO3/Si solar cells through employing thickness-controlled LaVO3 and a titanium oxide passivation layer

LaVO3 is well known as a promising material for use in photovoltaic devices because of its high absorption of visible light. Here, we report on the photovoltaic parameters and photostability of LaVO3/Si/TiOx solar cell devices. In this work, the photovoltaic parameters of the device are controlled via the thickness (t) of the LaVO3 layer; such control is possible because the transmittance, absorbance, and reflectance of this layer are dependent on its thickness. TiOx passivation is also used to reduce the recombination loss at the back surface. Furthermore, TiOx passivation improves the power conversion efficiency (PCE) by blocking recombination at the Si/metal interface. The LaVO3/Si/TiOx cells exhibit a maximum PCE of 6.78% at t = 70 nm. The PCE of the device shows only a 9% decrease after continuous 500 h irradiation at an intensity of 100 mW cm−2 at a temperature of 60 °C and 30–35% relative humidity, suggesting excellent long-term stability.

Organic amine surface modified one-dimensional CdSe0.8S0.2-diethylenetriamine/two-dimensional SnNb2O6 S-scheme heterojunction with promoted visible-light-driven photocatalytic CO2 reduction

Achieving a strong redox ability and high visible-light absorption ability in a single semiconductor material is difficult. Designing a heterojunction between two semiconductor materials is a feasible method. The new step (S-scheme) heterojunction can effectively promote the separation and transfer of photogenerated electron-hole pairs and retain strong redox ability. We designed and prepared a CdSe0.8S0.2-diethylenetriamine (DETA)/SnNb2O6 heterostructure material via the solvothermal method. When CdSe0.8S0.2-DETA and SnNb2O6 form an S-scheme heterojunction, 30%CdSe0.8S0.2-DETA/SnNb2O6 exhibits the highest CO production rate (17.31 μmol·g–1·h–1), which is factors of 2.8 and 4.8 higher than that of traditional solvothermal SnNb2O6 (6.2 μmol·g–1·h–1) and CdSe0.8S0.2-DETA (3.6 μmol·g–1·h–1), respectively. X-ray photoelectron spectroscopy characterization data provided evidence that the transfer pathway of space charge in the CO2 reduction process was in accordance with the S-scheme. This research provides a simple strategy through which one can optimize the band structure to promote the separation of photogenerated carriers and achieve a high efficiency of CO2 reduction.

Study on Challenges and Solutions for Enhancing Photocatalytic Activities of Ag3PO4 Nanoparticles for Degradation of Organic Dyes from Wastewater

Improper management of discharged waste material such as toxic organic dyes from industries causes severe health and economic problems because contaminated water with organic dyes is harmful to human being and aquatic ecosystems. The photocatalyst is a preferable wastewater treatment method because it is environmentally benign, cost‐wise, and more efficient in degrading dyes. Most metal oxide semiconductors are photocatalytic materials, but nowadays, Ag3PO4 nanoparticles have attracted enormous attention due to their low bandgap and high absorption of visible light. However, Ag3PO4 nanoparticles have low performance due to photocorrosion, high recombination rate, and instability in the solution. Thus, in this review article, the mechanism to enhance the photocatalytic activities of Ag3PO4 nanoparticles was discussed, and the future perspective of the silver phosphate was also stated.

Tunable type-II lateral MoSi2N4/WSi2N4 heterostructures for photocatalytic applications

Combining various two-dimensional crystals has emerged as an exciting way to tailor the properties of lateral heterostructures for new-generation optoelectronic devices. Herein, a seamless lateral heterostructure based on MoSi2N4 and MoSi2N4 monolayers along armchair interfaces is predicted, and its electronic and optical properties are investigated by using first principles calculations. Our calculations indicate that the MoSi2N4/WSi2N4 lateral heterostructures (HSs) possess excellent stability due to the very small lattice mismatch. In contrast to their parent monolayers with wide indirect band gaps, all (MoSi2N4)m(WSi2N4)n lateral HSs are direct gap semiconductors, and their direct gap nature is independent of compositions and strains. The band alignment of (MoSi2N4)m(WSi2N4)16-m lateral HSs undergoes a quasi-type-I to type-II to quasi-type-II to quasi-type-I band transition with an increase in m. (MoSi2N4)8(WSi2N4)8 is a type-II semiconductor, and the band arrangement changes from type-II to quasi-type-I upon applying tensile strain. Compared with pristine materials, the band edges of MoSi2N4/WSi2N4 lateral HSs are more favorable for photocatalytic water splitting. Furthermore, MoSi2N4/WSi2N4 lateral HSs exhibit higher visible light absorption. These results greatly expand the optoelectronic applications of Mxenes in the 2D realm.

Novel 2D HfTeS4 for water splitting with high visible-light absorption

Currently, photocatalysts have got much attention due to its promising application prospect in clean and reusable resources. In this paper, we have disclosed a novel monolayer HfTeS4 through first-principles calculations and the great stability of the HfTeS4 monolayer has been proved based on the formation energy, phonon spectrum and ab initio molecular dynamics. The HfTeS4 monolayer displays a remarkable absorbance capacity of up to 7.5 × 105 cm−1 in visible light region and a high carrier mobility of 864 cm−2 V−1 s−1. Both visible light absorbance capacity and carrier mobility are about 4 times larger than these properties of MoS2. Meanwhile, the anisotropy of carriers is beneficial to improve the photo-catalytic efficiency. Furthermore, tunable bandgaps under biaxial strain engineering are also provided. The results show that HfTeS4 monolayer can meet the conditions of photocatalysis in the strain range from -5% to 1%. Moreover, we surprisingly find that the HfTeS4 multilayers have proper band edges and much better light absorption ability than the monolayer, which ismore suitable for practical application. Our research reveals that all these fascinating properties make both monolayer and multilayer HfTeS4 a promising candidate for photocatalytic applications.

Electronic and optical properties of nitrogen and sulfur doped strontium titanate as efficient photocatalyst for water splitting: A DFT study

One of the most effective option of photocatalysts for water splitting is doped strontium titanate, SrTiO3. It has a high rate of photo-generated charge transfer and limited photocatalytic activity for water splitting. The search of an appropriate photocatalyst having a high visible light absorption as well as fast charge transportation is extremely needed, however it is a difficult task. The structural, electronic and optical properties of sulfur-doped SrTiO3 and nitrogen-doped SrTiO3 are investigated using calculations based on density functional theory (DFT). According to the band structure calculations, the O-2p states represented the higher levels of the valence band of pure SrTiO3. When S and N atoms are introduced into the SrTiO3 structure on the O site, electronic structure findings indicate that doping the Sulfur (S) atoms reduced the band gap significantly, whereas doping of N atoms increased the bandgap of SrTiO3. According to our results, the N-doped SrTiO3 has a sufficient band gap of 2.03 eV, as well as suitable high visible light absorption and charge carrier transportation. The optical properties showed that N-doped SrTiO3 has good photosensitivity for visible light. In addition, we have found a significant impurity state that differs from O 2p-states, which can increase photocatalytic efficiency. The results of studies of electronic band structure showed that electron-hole transportation was well consistent with the experimental data. Thus, the N-doped SrTiO3 in this study is indeed an attractive candidate for hydrogen evolution throughout the visible light range, providing a logical base for the establishment of innovative photocatalysts.

Thermal, microstructural, optical, magnetic and magnetocaloric studies for Ni0.5Mn0.5Cr2O4 chromite spinel prepared using sol-gel method

• The Ni 0.5 Mn 0.5 Cr 2 O 4 chromite spinel was prepared using sol-gel method. • The phase transformation for the sample was confirmed using TGA and DSC analyses. • The sample crystallizes in the cubic spinel structure with F d 3 ¯ m space group. • The prepared material has higher absorption of visible light in the photocatalytic reactions. • Magnetocaloric properties for the sample are quite comparable to several literature values found for other chromite spinels. In this work, the properties of the Ni 0.5 Mn 0.5 Cr 2 O 4 chromite spinel prepared using sol-gel method were investigated. The TGA and DSC analyses were used to study the spinel phase formation and the weight loss during the synthesis process for the sample. The XRD and TEM characterizations confirmed the development of the cubic spinel structure. From the FTIR spectrum, the characteristics vibrational modes corresponding to the spinel structure were observed. From the room temperature UV–Vis optical absorbance, the synthesized chromite sample shows a significantly lower direct band gap ( E gd = 1.90 eV) and has an appropriate absorption rate in the visible light region. Magnetization ( M - T curve) shows a second order magnetic phase transition from the ferrimagnetic (FiM) behavior to the paramagnetic (PM) behavior at the Curie temperature T C = 40 K. By comparing our results to those previously found for the NiFe 2 O 4 spinel, we can conclude that the substitution of Mn for NiFe 2 O 4 increases its magnetization and decreases its coercivity. The magnetocaloric performances achieved for Ni 0.5 Mn 0.5 Cr 2 O 4 sample are quite comparable to several literature values found for other chromite spinels.

Amplified detection signal at a photoelectrochemical aptasensor with a poly(diphenylbutadiene)-BiOBr heterojunction and Au-modified CeO2 octahedrons

A major aspect of this work is the synergistic application of a poly(diphenylbutadiene)-BiOBr composite and a gold nanoparticle-linked CeO2 octahedron to develop a photoelectrochemical aptasensor with an easily measurable detection signal change. Specifically, poly(diphenylbutadiene) nanofiber-immobilised BiOBr flower-like microspheres were developed as a hybrid material with a heterojunction that facilitates high visible light absorption and efficient photo-generated charge separation, which are essential features for sensitive photoelectrochemical sensors. The model analyte acetamiprid was attached via its specific aptamer on the aptasensor. Separately, a gold nanoparticle-linked CeO2 octahedron was strategically used to significantly diminish the photocurrent by impeding electron transfer at the aptasensor surface. After acetamiprid binding, the CeO2 octahedrons were displaced from the aptasensor. This caused a weakened quenching effect and restored the photocurrent to accomplish an "on-off-on" detection mechanism. This photoelectrochemical aptasensor exhibited a detection limit of 0.05 pM over a linear range of 0.1 pM–10 μM acetamiprid. The use of an aptamer has provided good specificity to acetamiprid and anti-interference. In addition, an ∼5.8% relative standard deviation was estimated as the reproducibility of the photoelectrochemical aptasensor. Furthermore, nearly 90% of the initial photocurrent was still measurable after storing these aptasensors at room temperature for 4 weeks, demonstrating their stability.

Photocatalytic Degradation of Sulfamethoxazole, Nitenpyram and Tetracycline by Composites of Core Shell g-C3N4@ZnO, and ZnO Defects in Aqueous Phase.

The synthesis of photocatalysts with high charge separation and transfer efficiency are of immense significance in the process of using photocatalysis technology for wastewater treatment. In this study core shell g-C3N4@ZnO, and ZnO defects photocatalysts presented an improved morphology in its characterization using techniques such as SEM, DRS, PL, MS, EIS, and XRD, and enhanced photodegradation of sulfamethoxazole, Nitenpyram and Tetracycline. Different composites were obtained as confirmed by the various characterization techniques studied, including core shell g-C3N4@ZnO, and ZnO defects photocatalyst. The synthesized photocatalysts showed high visible light absorption efficiency within a range of ~655 to 420 nm. Core shell g-C3N4@ZnO, and ZnO defects photocatalysts demonstrated high photocatalytic activity ascribed to high load separation and transition as shown in PL, Photocurrent reaction and EIS. It is understandable that core shell g-C3N4@ZnO, and ZnO defects photocatalysts have been confirmed to be one of the ultimate promising entrants for photocatalyst scheming.

MoS2 (1T/2H)/g-C3N4 heterojunctions created via Mo seed growth in situ towards high photo- and electro-chemical performance

• MoS 2 /g-C 3 N 4 (MSCN) composite was prepared via Mo as seeds by a solvothermal synthesis. • The improved MoS 2 /g-C 3 N 4 interface enhanced photo- and electro-chemical performance. • The composite revealed the degradation rate of 2,4-dichlorophenol up to 84.1%. • The photocatalytic hydrogen production rate of the composite was 1683.9 μmol/g/h. It is an effective way to construct graphic carbon nitrate (g-C 3 N 4 ) based heterostructures with strong interfacial effect for improving their photocatalytic performance. In this paper, Mo was introduced into g-C 3 N 4 nanosheets as seeds to create MoS 2 /g-C 3 N 4 (MSCN) composite material by a solvothermal synthesis at low temperature. The interface between MoS 2 and g-C 3 N 4 was therefore improved, in which MoS 2 exhibited 1T and 2H phases. Compared with pure CN, the MSCN composite material broadened the light absorption range, enhanced the charge transfer kinetics and reduced the recombination of photogenerated carriers. The photo- and electro-chemical characterization indicated that sample MSCN-6 revealed the best photocatalytic performance, in which the degradation rate of 2,4-dichlorophenol was up to 84.1% and the photocatalytic hydrogen production rate was 1683.9 μmol/g/h, which were 1.67 and 3.61 times of those of pure g-C 3 N 4 , respectively. The quenching experiment of the active substance demonstrated that h + was the contributing active substances. The result provides new idea for designing composite photocatalysts with high efficiency, high visible light absorption and strong interface coupling.

Revealing the stability of CuWO4/g-C3N4 nanocomposite for photocatalytic tetracycline degradation from the aqueous environment and DFT analysis

Graphitic carbon nitride (g-C3N4) is an emerging metal-free photocatalyst, however, engineering the photocatalytic efficiency for the effective degradation of hazardous molecules is still challenging. An unstable and low bandgap CuWO4 was composited with g-C3N4 to achieve synergistic benefits of tuning the visible light responsiveness and stability of CuWO4. CuWO4/g-C3N4 nanocomposite exhibited a relatively high visible light absorption region and the bandgap was modified from 2.77 to 2.53 eV evidenced via UV-DRS. Moreover, the fast electron transfer rate was observed with CuWO4/g-C3N4 nanocomposite as confirmed using PL and photocurrent studies. XRD, FT-IR, and HR-TEM analyses signified the formation of CuWO4/g-C3N4 nanocomposite. CuWO4/g-C3N4 nanocomposite showed enhanced photocatalytic degradation of Tetracycline (TC) about ∼7.4 fold greater than pristine g-C3N4 in 120 min. Notably, the OH• and •O2− radicals played a most significant role in photocatalytic TC degradation. Furthermore, the energy band structure, density of state, and Bader charge analyses of these molecules were performed.

Perovskite semiconductor-engineered cascaded molecular energy levels in naturally-sensitized photoanodes

Naturally-sensitized photoanodes in dye-sensitized solar cells (DSSCs) are promising alternatives to enhance photoabsorption, electron excitation/injection, but voltage loss remains a challenge. Here, we focus on understanding the cascading of energy levels in perovskite semiconductor cosensitized naturally-sensitized photoanodes to leverage forward charge transport addressing the voltage loss arising from ITO/TiO2 heterojunction's built-in potential. The β-carotene-sensitized TiO2 photoanode modified with methylammonium lead iodide (MAPbI3) co-sensitizer causes an upward shifting in TiO2 Fermi level (EF). This phenomenon is predominantly attributed to increased initially injected electrons due to low MAPbI3 bandgap and high visible-light absorption. Enhanced charge separation and injection mechanisms at the TiO2/MAPbI3 interface increase the effective density-of-states (DOS >2.46 × 1021 cm−3) in the TiO2 conduction band (CB) and hence decrease its work function to 4.82 eV. The decrease in TiO2 work function suppressed CB bending at ITO/TiO2 heterojunction, which minimized the photoinduced electrostatic potential barrier up to 13.1%. The reduced Schottky barrier (φSBH<0.52 eV) only allows electrons tunneling, while inhibited back-electron transport reduced both current leakage and voltage loss yielding in high open-circuit voltage (Voc increase by 120%) and power conversion efficiency (PCE increase by 240%). The MAPbI3 incorporation also broadened photoanode absorbance by 2-fold, paving the way towards perovskite semiconductor cosensitization to avoid voltage loss from bio-integrated photoanodes for photovoltaic and other optoelectronic and photonic applications. Future works will focus on studying the series resistance, cathode electrode coating uniformity, recombination kinetics, solid electrolytes, as well as other aspects typically related to increasing the photocurrent levels of this β-carotene-sensitized solar cell.

Role of Interfacial Defects in Photoelectrochemical Properties of BiVO4 Coated on ZnO Nanodendrites: X-ray Spectroscopic and Microscopic Investigation.

Synchrotron-based X-ray spectroscopic and microscopic techniques are used to identify the origin of enhancement of the photoelectrochemical (PEC) properties of BiVO4 (BVO) that is coated on ZnO nanodendrites (hereafter referred to as BVO/ZnO). The atomic and electronic structures of core-shell BVO/ZnO nanodendrites have been well-characterized, and the heterojunction has been determined to favor the migration of charge carriers under the PEC condition. The variation of charge density between ZnO and BVO in core-shell BVO/ZnO nanodendrites with many unpaired O 2p-derived states at the interface forms interfacial oxygen defects and yields a band gap of approximately 2.6 eV in BVO/ZnO nanocomposites. Atomic structural distortions at the interface of BVO/ZnO nanodendrites, which support the fact that there are many interfacial oxygen defects, affect the O 2p-V 3d hybridization and reduce the crystal field energy 10Dq ∼2.1 eV. Such an interfacial atomic/electronic structure and band gap modulation increase the efficiency of absorption of solar light and electron-hole separation. This study provides evidence that the interfacial oxygen defects act as a trapping center and are critical for the charge transfer, retarding electron-hole recombination, and high absorption of visible light, which can result in favorable PEC properties of a nanostructured core-shell BVO/ZnO heterojunction. Insights into the local atomic and electronic structures of the BVO/ZnO heterojunction support the fabrication of semiconductor heterojunctions with optimal compositions and an optimal interface, which are sought to maximize solar light utilization and the transportation of charge carriers for PEC water splitting and related applications.