Decreased Charge Recombination Research Articles

Enhancing electrochemical performance of Co3O4/ZnO composite nanostructures through interface engineering for oxygen evolution reaction

Co3O4/ZnO composite nanostructures were successfully synthesized via a simple hydrothermal method followed by air-based calcination at 500°C. The resulting hexagonal heterostructure composite with a large interfacial area demonstrates exceptional oxygen evolution electrocatalytic activity with an overpotential of 288 mV at 10 mA cm-², and a low Tafel slope (80 mV dec⁻¹). This enhanced activity is attributed to the Co3O4/ZnO p-n junction, where ZnO (an n-type semiconductor) and Co3O4 (a p-type semiconductor) meet, which is crucial for boosting catalytic activity. This interface enables swift electron movement between the two materials, resulting in better charge separation and decreased charge recombination. Additionally, the high active surface area, confirmed by cyclic voltammetry measurements, further contributes to the improved OER performance. The well-defined interfaces within the Co3O4/ZnO heterostructures provide abundant active sites, facilitating efficient charge transfer kinetics. This research highlights the potential of composite heterostructures as promising electrocatalysts for water-splitting applications.

Rational design of ZnO/SrTiO3 S-scheme heterojunction for photo-enhanced piezocatalytic hydrogen production

Photopiezocatalysis have been frequently investigated for hydrogen evolution reactions in recent years. Herein, ZnO, SrTiO3 and ZnO/SrTiO3 S-scheme heterojunction were investigated for photo/piezocatalytic hydrogen production. Piezocatalytic hydrogen production under ultrasonic vibration by using ZnO, SrTiO3 and ZnO/SrTiO3 was obtained as 270 µmol g-1h−1, 200 µmol g-1h−1 and 1265 µmol g-1h−1, respectively. In addition, ZnO/SrTiO3 S-scheme heterojunction showed 2200 µmol g-1h−1 photopiezocatalytic hydrogen production under simultaneous exposure to white LED light and ultrasonic sound. ZnO/SrTiO3 heterojunction displayed significantly higher hydrogen production rate due to the decreased charge recombination, increased charge transfer with strong piezoelectric polarization and internal electrical field. The piezoelectric effect of ZnO/SrTiO3 heterojunction is also confirmed by piezoresponse force microscope technique with butterfly and phase hysteresis loops. Also, piezoelectric coefficient of ZnO/SrTiO3 found about 2-folds higher than those of their pristine forms. Electron transfer and reaction mechanism of ZnO/SrTiO3 and activity differences are confirmed by advanced optical and electrochemical techniques such as diffuse reflectance spectroscopy, electronic impedance spectroscopy, Mott-Schottky calculation and chronoamperometry. The whole electrochemical measurements have been performed with or without mechanical stress and light irradiation, which signify their band bending properties, electron transfer mechanism and catalytic activities.

The Development of Metal-Free Porous Organic Polymers for Sustainable Carbon Dioxide Photoreduction.

A viable tactic to effectively address the climate crisis is the production of renewable fuels via photocatalytic reactions using solar energy and available resources like carbon dioxide (CO2) and water. Organic polymer material-based photocatalytic materials are thought to be one way to convert solar energy into valuable chemicals and other solar fuels. The use of porous organic polymers (POPs) for CO2 fixation and capture and sequestration to produce beneficial compounds to reduce global warming is still receiving a lot of interest. Visible light-responsive organic photopolymers that are functionally designed and include a large number of heteroatoms and an extended π-conjugation allow for the generation of photogenerated charge carriers, improved absorption of visible light, increased charge separation, and decreased charge recombination during photocatalysis. Due to their rigid structure, high surface area, flexible pore size, permanent porosity, and adaptability of the backbone for the intended purpose, POPs have drawn more and more attention. These qualities have been shown to be highly advantageous for numerous sustainable applications. POPs may be broadly categorized as crystalline or amorphous according to how much long-range order they possess. In terms of performance, conducting POPs outperform inorganic semiconductors and typical organic dyes. They are light-harvesting materials with remarkable optical characteristics, photostability, cheap cost, and low cytotoxicity. Through cocatalyst loading and morphological tweaking, this review presents optimization options for POPs preparation techniques. We provide an analysis of the ways in which the preparative techniques will affect the materials' physicochemical characteristics and, consequently, their catalytic activity. An inventory of experimental methods is provided for characterizing POPs' optical, morphological, electrochemical, and catalytic characteristics. The focus of this review is to thoroughly investigate the photochemistry of these polymeric organic photocatalysts with an emphasis on understanding the processes of internal charge generation and transport within POPs. The review covers several types of amorphous POP materials, including those based on conjugated microporous polymers (CMPs), inherent microporosity polymers, hyper-crosslinked polymers, and porous aromatic frameworks. Additionally, common synthetic approaches for these materials are briefly discussed.

Alkyl effects on charge recombination in copper electrolyte-based dye-sensitized solar cells: Insights for targeted molecular design towards high performance

Two quinoxaline dyes utilized in copper-electrolyte-based dye-sensitized solar cells (Cu-DSSCs) are theoretically investigated to analyze the impact of alkyl chains on dye performance. The investigation shows that ZS4, known for its record efficiency of up to 13.2 %, exhibits higher electron coupling and fewer binding sites for dye-[Cu(tmby)2]2+ interaction compared to ZS5. Contrary to common belief, alkyl chains are found to not only provide shielding but also hinder the interaction between dye and [Cu(tmby)2]2+ by influencing the optimal conformation of dyes, thereby impeding the charge recombination process. It is crucial to consider the influence of alkyl chains on dye conformation when discussing the relationship between dye structure and performance, rather than oversimplifying it as often done traditionally. Building on these findings, eight dyes are strategically designed by adjusting the position of the alkyl chain to further decrease charge recombination compared to ZS4. Theoretical evaluation of these dyes reveals that changing the alkyl chain on the nitrogen atom from 2-ethylhexyl (ZS4) to 1-hexylheptyl (D3-2) not only reduces the charge recombination rate but also enhances light harvesting ability. Therefore, D3-2 shows potential as a candidate for experimental synthesis of high-performance Cu-DSSCs with improved efficiency.

Morphologic and microstructural modulation of graphitic carbon nitride through EDTA-2Na mediated supramolecular self-assembly route: Enhanced visible-light-driven photocatalytic activity for antibiotic degradation

Photocatalysis technology is a promising green route to eliminate antibiotic residues, but current performance still cannot satisfy the practicality. Herein, an EDTA-2Na mediated supramolecular self-assembly strategy was employed to modulate the morphology and microstructure of graphitic carbon nitride (GCN). The obtained EDTA-2Na mediated supermolecule-based GCN (ESGCN) was proved to possess ultrathin flake-like morphology with developed porous structure and Na/O dopants to enhance visible light harvesting. Compared to the pristine GCN and the supermolecule-based GCN (SGCN) without the EDTA-2Na mediation, the ESGCN has more photogenerated charges, decreased charge recombination and accelerated transport/transfer rate, which thus greatly improved photocatalytic activity for degrading tetracycline hydrochloride (TC) and the apparent rate constant is 37.3 and 6.0 times higher than those of the GCN and the SGCN. Additionally, it exhibits excellent universality in degrading various tetracycline antibiotics with a wide pH range and good stability/durability. A possible mechanism of photocatalytic degradation of TC by the ESGCN was elaborated. And the toxicity assessments and mung bean germination experiments also indicate the photocatalytic process can effectively decrease the toxicity and the potential risk of TC to the environment. This work provides a feasible and effective approach to enhance photocatalytic activity of graphitic carbon nitride, which has prominent potentials for elimination of antibiotic residues in environment.

Correlation between phase composition and physicochemical properties in Cu-, Mo-, and W- doped bismuth vanadate

We report a detailed study about the correlation between the physicochemical properties of solvothermally synthesized pristine and 1 %, 2.5 %, and 5 % Cu, Mo, and W-doped bismuth vanadate (BiVO4, BVO) with its phase composition. The effect of the dopant and the duration of synthesis (8 h and 20 h) on the physicochemical properties of BVO allowed us to tune the ratio of monoclinic scheelite to tetragonal zircon phase in BVO powders. This approach helped us to establish the relationship between the presence of monoclinic scheelite or tetragonal zircon phase with structural, morphological and optical properties of BVO powders, obtained by different physicochemical methods (e.g. X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Raman spectroscopy, X-ray Photoelectron Spectroscopy (XPS), Diffuse Reflectance Spectroscopy (DRS) and Photoluminescence spectroscopy (PL)). The results indicated that, in addition to XRD, Raman, and DRS, several other methods could distinguish between the two phases. For example, SEM analysis revealed that monoclinic scheelite BVO exhibits either elongated assemblies of cube-like particles or prismatic particles with sizes ∼500 nm. In contrast, tetragonal zircon BVO exclusively exhibited porous spherical particles with diameter ∼2 μm. DRS and Raman spectroscopy indicated that there is a possibility of distinguishing between the two phases if their shares are large enough. For instance, monoclinic BVO showed band gap values in the range of 2.35–2.52 eV, while tetragonal zircon BVO exhibited values in the range of 2.80–3.00 eV. XPS showed a correlation between phase composition and surface chemistry of BVO only for Cu-doped samples, revealing the presence of Cu+ in monoclinic BVO and the presence of both Cu+ and Cu2+ in tetragonal zircon BVO. PL showed that monoclinic scheelite BVO displayed decreased charge recombination compared to tetragonal zircon BVO. Deeper insight into the correlation between the physicochemical properties and phase composition of Cu, Mo, and W-doped bismuth vanadate (BiVO4, BVO) was based on water/pentanol medium (2:1 vol%) as a novel synthesis pathway. This may open new avenues for the broader methodological exploration of surface chemistry, particle size, and morphology of BVO particles through the use of diverse functionalization agents. Finally, the established links between phase composition and structural, morphological, and other physicochemical properties provide new and more predictable opportunities for further improvement of BVO properties for various applications.

Green Synthesis of Pristine and Ag-Doped TiO2 and Investigation of Their Performance as Photoanodes in Dye-Sensitized Solar Cells.

Dye-sensitized solar cells (DSSCs) have emerged as a potential candidate for third-generation thin film solar energy conversion systems because of their outstanding optoelectronic properties, cost-effectiveness, environmental friendliness, and easy manufacturing process. The electron transport layer is one of the most essential components in DSSCs since it plays a crucial role in the device's greatest performance. Silver ions as a dopant have drawn attention in DSSC device applications because of their stability under ambient conditions, decreased charge recombination, increased efficient charge transfer, and optical, structural, and electrochemical properties. Because of these concepts, herein, we report the synthesis of pristine TiO2 using a novel green modified solvothermal simplistic method. Additionally, the prepared semiconductor nanomaterials, Ag-doped TiO2 with percentages of 1, 2, 3, and 4%, were used as photoanodes to enhance the device's performance. The obtained nanomaterials were characterized using XRD, FTIR, FE-SEM, EDS, and UV-vis techniques. The average crystallite size for pristine TiO2 and Ag-doped TiO2 with percentages of 1, 2, 3, and 4% was found to be 13 nm by using the highest intensity peaks in the XRD spectra. The Ag-doped TiO2 nanomaterials exhibited excellent photovoltaic activity as compared to pristine TiO2. The incorporation of Ag could assist in successful charge transport and minimize the charge recombination process. The DSSCs showed a Jsc of 8.336 mA/cm2, a Voc of 698 mV, and an FF of 0.422 with a power conversion efficiency (PCE) of 2.45% at a Ag concentration of 4% under illumination of 100 mW/cm2 power with N719 dye, indicating an important improvement when compared to 2% Ag-doped (PCE of 0.97%) and pristine TiO2 (PCE of 0.62%).

Over 19.1% efficiency for sequentially spin-coated polymer solar cells by employing ternary strategy

Series of sequentially spin-coated polymer solar cells (SS-PSCs) are fabricated with donor layers containing PM1, D18 or PM1:D18 and sequentially spin-coated L8-BO acceptor layer. Photon harvesting of donor layers could be enhanced by optimizing the weight ratios of PM1 to D18 due to their distinct optical band-gap. The optimized ternary SS-PSCs exhibit a power conversion efficiency of 19.13%, resulting from the simultaneously enhanced short-circuit-current density (JSC) of 27.20 mA/cm2, open-circuit voltage (VOC) of 0.90 V and fill factor of 78.53% in comparison to those of PM1/L8-BO based SS-PSCs. The increased JSCs of ternary SS-PSCs is due to the enhanced photon harvesting and efficient exciton utilization assisted by an additional channel from D18 to PM1 through energy transfer. The increased VOC of optimal ternary SS-PSCs benefits from the little larger VOC of binary SS-PSCs with D18 as donor layer. The donor/acceptor interfacial energy is slightly increased by incorporating D18 in donor layer, which is conducive to form the optimized vertical phase separation to decrease charge recombination loss. This work indicates that ternary strategy is also a versatile and effective method in improving the performance of SS-PSCs.

Photoluminescence and enhanced photocatalytic activity of mechanically activated graphite-zinc oxide composites

In this work, we show evidence of enhanced photocatalytic activity in mechanically activated graphite-zinc oxide (ZnO) composites using time-resolved photoluminescence (TRPL) and time-integrated photoluminescence (TIPL) spectroscopy. The graphite-ZnO composites were synthesized through facile mixing and grinding of graphite and ZnO precursors without any heat treatment. The precursors were ground at room temperature with varying graphite to ZnO mass ratios of 3:1, 2:2, and 1:3 for 0, 2, and 4 h. Raman spectroscopy and x-ray diffractometry confirm the presence of both graphite and ZnO and corroborate the graphite-to-ZnO ratio. XRD results also show a hexagonal wurtzite ZnO crystal structure. To determine the photocatalytic activity of the composites, the degradation of methylene blue (MB) under UV light was measured with a UV–vis spectrophotometer. Nearly full degradation was achieved within a half hour for all composite samples. The kinetic rates of 0.10 min−1 were also estimated for mixed and unground samples and samples ground for 2 h. Time-resolved photoluminescence (TRPL) and time-integrated photoluminescence (TIPL) spectroscopy reveal longer lifetimes and more intense UV emissions, respectively, for composite samples compared to pure ZnO. We propose that the even agglomeration of zinc oxide particles on graphite due to grinding enhances the photocatalytic degradation by the zinc oxide. TRPL and TIPL spectroscopy implies the excellent binding between ZnO and graphite, which greatly contributes to the decreased charge recombination resulting in the superior photocatalytic activity observed with our samples.

Organic bromide solutions-processed all-inorganic perovskite for efficient and stable photovoltaics

All-inorganic CsPbI3-x Br x perovskites with appropriate band gap is an attractive semiconductor material for solar applications, whereas their phase stability plays a key role in high-efficiency perovskite solar cells (PSCs). Their device performance was severely constrained by defects, here we found that the promising phenylpropylamine bromide (PPABr) as a simple additive can effectively influence the crystallization kinetics and produce a bifunctional treatment of perovskite, Br ion doping, and organic cation surface passivation. The PPABr treatment has essentially little influence on the light absorption capacity of CsPbI3-x Br x , the band gap is somewhat widened, and the surface hydrophobicity and phase stability are enhanced. CsPbI3-x Br x perovskites treated with PPABr have altered interfacial properties and obtained better interfacial contact, resulting in improved charge extraction and decreased charge recombination. Furthermore, 2.5 mol% PPABr treated CsPbI3-x Br x -based PSCs exhibited repeatable photovoltaic performance with a maximum efficiency of 13.14%. Within 150 h under air circumstances, the PCE attenuation is controlled to within 5% during the test. Hence, passivating inorganic perovskite using organic bromides PPABr is a novel and promising strategy for developing stable, high-performance solar cells.

Alkynyl carbon functionalized N-TiO2: Ball milling synthesis and investigation of improved photocatalytic activity

Herein, a series of alkynyl carbon functionalized N-TiO2 is fabricated by ball milling of CaC2 and pre-prepared N-TiO2. Based on the X-ray diffraction, X-ray photoelectron spectroscopy, and high-resolution transmission electron microscopy techniques, it is confirmed that the alkynyl carbon materials are successfully doped into N-TiO2. The visible light catalytic performance of the alkynylated N-TiO2 (CNT-0.1) for degradation of Rhodamine B, methylene blue, levofloxacin, and p-nitrophenol is higher than that of the N-TiO2. Further, the photocatalytic NH3 production over the alkynylated N-TiO2 is 83.11 μmol·h−1·g−1 in the presence of CH3OH as the proton source, which is 2.41 folds higher than that of the N-TiO2 under UV-Visible light irradiation. The dominant active species for the photodegradation of Rhodamine B are determined to be h+ and O2·- radicals. The photocatalytic stability is verified by the recyclable tests, demonstrating a little decrease in the Rhodamine B photodegradation performance. It can be concluded from the photo-current, photo-voltage, electrochemical impedance spectroscopy, photoluminescence spectra, UV–vis absorption spectra, and Mott-Schottky plots that modification of alkynyl carbon materials can decrease charge recombination and improve the visible light response capacity of the photocatalyst, finally resulting in the enhanced photocatalytic performance. This work illustrates that the introduction of alkynyl carbon into semiconductor materials is a very promising modification strategy for promoting their photocatalytic properties.

Optimizing the charge migration pathways via embedding Pd NPs in porous TiO2 for boosting photocatalytic H2 production

A well designed cocatalyst loading structure is one of the crucial factors for photocatalytic H2 production. The effectiveness of embedded cocatalyst for the enhancement of photocatalysis still needs to be confirmed. Herein, the porous titanium dioxide embedded with Pd (Pd@TiO2) was successfully obtained by calcination of Pd@MIL-125 as precursor, which was prepared in situ by solvothermal reaction. The characterization results showed that ∼78% of Pd nanoparticles were successfully encapsulated in the catalyst with good dispersion. The surface area of Pd@TiO2 increased from 96.0 to 131.7 m2/g compared with surface loading catalyst Pd/TiO2. Photocatalytic hydrogen production reactions showed that the activity of Pd@TiO2 reached 4.065 mmol/h/g with the apparent quantum efficiency of 22% at 350 nm, which was 2.5 times that of the external loading Pd/TiO2 catalyst prepared by traditional impregnation method and 4.8 times that of the commercial catalyst Pd/P25. The dynamic characterizations showed that Pd@TiO2 exhibited enhanced charge separation efficiency, decreased charge recombination rate, and decreased charge transfer resistance, which promoted the charge utilization and made Pd@TiO2 an excellent photocatalyst. This study provided an effective strategy for the design of Pd embedded porous TiO2 photocatalyst and confirmed that the embedding of cocatalyst is an effective strategy for the design of H2 production photocatalyst.

Morphology modulated brookite TiO2 and BaSnO3 as alternative electron transport materials for enhanced performance of carbon perovskite solar cells

Designing alternatives to TiO2 electron-transport layers (ETLs) for facile electron extraction and transport to enhance the efficiency of n-i-p structured carbon perovskite solar cells (CPSC) is still a less explored research interest. In this work, the combined effect of the phase and morphology of BaSnO3 (BSO) and brookite TiO2 (BTO) nanostructured materials are explored as alternative electron transport layers (ETLs) instead of dominating anatase TiO2 in CPSC. The highest power-conversion efficiencies (PCEs) of CPSCs with rod-shaped BTO and BSO were recorded at ∼15.02% and ∼13.4%, respectively, which claims the highest efficiency for BTO and BSO CPSCs in ambient conditions to the best of our knowledge. In addition, our findings indicate that the CPSC's with rod structured BTO and BSO exhibited decreased charge recombination and improved efficiency compared to concerning spherical morphologies (12.5% for BSO nanoparticles) and cubic particles (14% for BTO nanocubes) due to the superior photogenerated charge-carrier extraction and enhanced interface quality. This research will open the door for various morphologies of alternative ETL materials and their physicochemical understanding toward achieving high-efficiency ambient CPSCs.

Anion-Doped Thickness-Insensitive Electron Transport Layer for Efficient Organic Solar Cells.

In organic solar cells, interfacial materials play essential roles in charge extraction, transportation, and collection. Currently, highly efficient and thickness-insensitive interfacial materials are urgently needed in printable large area module devices. Herein, water/alcohol-soluble conjugated polyelectrolyte PFNBT-Br, with medium bandgap based on benzothiadiazole, are doped by two alkali metal sodium salts, NaH2 PO2 , Na2 C2 O4 with different counter anions, to pursue high efficiency and thickness-insensitive electron-transport layers. Results show that the doping of electron-transport material can effectively promote the performance of the devices. Moreover, electron-transport layers doped by these salts with different counter anions show different behaviors in performances. Among which, the salt with oxalate anion C2 O4 2- (also named Ox2- ) shows much better device performance than the salt with hypophosphite anion (H2 PO2 - ), especially under the thick film condition (e.g., 50 nm). The greatly enhanced performances of interfacial material doped by Ox2- are due to reduced series resistance between the active layer material and the electrode, reduced dark-current, improved charge transport, and extraction efficiency, and decreased charge recombination for the devices at thick-film condition. These results demonstrated that n-doping could be a great potential strategy for making thickness-insensitive interfacial layers, besides, the performances can be further improved by carefully selecting salts.

Exploring the influence of Zn2SnO4/ZIF-8 nanocomposite photoelectrodes on boosting efficiency of dye sensitized solar cells

It is imperative to develop innovative efficient photoelectrode materials for high-performance dye-sensitized solar cells (DSSCs). In this work, cubic spinel Zn2SnO4 (ZTO)+(5, 10, 15, 20%) zeolite imidazole framework-8 (ZIF-8) nanoparticles were applied as photoanode materials of DSSC devices. The Zn2SnO4 was effectively synthesized in a simple and cost-effective manner by carefully controlling the hydrothermal conditions. The Zn2SnO4/ZIF-8 nanocomposite photoelectrodes were coated over the TiO2 compact layer to decrease charge recombination at the transparent conductive oxide/mesoporous interface. The X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDS), diffuse reflectance spectroscopy (DRS), photoluminescence (PL), Brunauer–Emmett–Teller (BET) isotherms, Fourier transform infrared spectroscopy (FT-IR) and electrochemical impedance spectroscopy (EIS) analysis methods were used to study the properties of all nanostructured photoanodes. In addition, the effects of Zn2SnO4/ZIF-8 nanocomposites were evaluated on DSSCs performances. The results clearly showed that adding ZIF-8 to Zn2SnO4 improved the photovoltaic performance of the fabricated DSSCs. Furthermore, compared to pure Zn2SnO4 NPs, Zn2SnO4+15% ZIF-8 increased open circuit voltage (VOC) from 0.64 to 0.77 V and short current density (JSC) from 6.89 to 11.27 mA/cm2. The Zn2SnO4+15% ZIF-8 photoanodes increased the power conversion efficiency (PCE) of DSSC by about 195% (from 2.02 to 3.94%) relative to the pure ZTO photoanode. This was due to the fact that the Zn2SnO4+15% ZIF-8 nanocomposite had the quickest electron transport rate, the best electron collecting efficiency, and the greatest charge recombination resistance, all of which are extremely advantageous to improve device efficiency.

Investigation on the Mechanism of Radical Intermediate Formation and Moderate Oxidation of Spiro-OMeTAD by the Synergistic Effect of Multisubstituted Polyoxometalates in Perovskite Solar Cells.

Conventional oxidation of 2,2',7,7'-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9'-spirobifluorene (Spiro-OMeTAD) by air would bring various drawbacks for perovskite solar cells (PSCs), such as low power conversion efficiency (PCE) and poor stability. Here, a series of heteroatom-substituted Keggin-type polyoxometalates (POMs), H4PMo11VO40 (PMo11V), H5PMo10V2O40 (PMo10V2), and H6PMo9V3O40 (PMo9V3) are prepared and applied as p-type dopants to realize quantitative and controllable oxidation of Spiro-OMeTAD under an inert condition. The possible mechanism and electron donor regions in the oxidation of Spiro-OMeTAD are investigated using two-dimensional nuclear magnetic resonance (NMR) spectra and the relationship between POM structures and the oxidation degree of Spiro-OMeTAD is proposed. In addition, the synergistic effect of heteroatoms makes V2-substituted PMo10V2 exhibit appropriate oxidation of Spiro-OMeTAD and promoted the highest efficient hole extraction as well as the decreased charge recombination. Therefore, the champion device doped with PMo10V2 shows a PCE of 20.41% and a superior open circuit voltage (Voc) of 1.133 V, surpassing that of the pristine device (18.61%). This work presents a fresh perspective to the controllable oxidation of Spiro-OMeTAD employing economical inorganic POM dopants, which would promote the commercialization of PSCs.

Electron acceptor design for 2D/2D iodinene/carbon nitride heterojunction boosting charge transfer and CO2 photoreduction

Harvesting value-added products by CO2 reduction through photocatalysis is a sustainable approach. Against halogen-doping treatment, few-layer iodinene (FLI2) was used innovatively to construct 2D/2D van der Waals heterojunction with carbon nitride nanosheets (CNNS) for CO2 reduction under visible light irradiation. The photocatalyst achieved an enhanced CO production rate of 34.22 μmol g-1h−1, which was 7.76 times as pristine CNNS. Improved activity was attributed to FLI2/CNNS maintained tri-s-triazine crystal structure and polymeric framework of CNNS. FLI2/CNNS formed a contact interface by van der Waals force, where FLI2 served as an electron acceptor and CNNS acted as an electron donor, beneficial for electron transfer. This carrier migration tendency in FLI2/CNNS was confirmed by the DFT calculation of Fermi level and electron density distribution, which led to increased charge separation and decreased charge recombination. This work proposes the novel 2D/2D FLI2/CNNS and highlights the potential of metal-free heterojunction for efficient photocatalysis.

Enhancing the photocurrent response of cesium bismuth iodide perovskite using a CuO nanocones array as the hole collecting layer

A CuO nanocones array (NCA) is introduced as a hole collecting layer for a top light-incident Cs3Bi2I9 perovskite photodetector. Its photocurrent response (i-t) shows that the photocurrent of the CuO-NCA/Cs3Bi2I9 device, and its responsivity, are one order of magnitude higher than that of the CuO thin film/Cs3Bi2I9 based device. Moreover, the increased interfacial area between the Cs3Bi2I9 and CuO-NCA facilitates hole collecting. While the transfer of the photogenerated holes is more effective and straightforward in aligned nanocones, which contributes to a larger photocurrent. The dynamics of the photo-generated charge transport also indicates a significantly improved charge transfer and a decreased charge recombination in the CuO-NCA/Cs3Bi2I9 based device.

Simultaneous doping of sulfur and chloride ions into ZnO nanorods for improved photocatalytic properties towards degradation of methylene blue

In this study, we have successfully doped sulfide (S−2) and chloride (Cl−1) simultaneously into ZnO by hydrothermal method. The structure, morphology, composition, and optical properties of the prepared S–Cl doped ZnO nanostructures were investigated by x-ray diffraction (XRD), scanning electron microscopy (SEM), scanning transmission electron microcopy (STEM), energy dispersive spectroscopy (EDX) and UV–visible (UV–Vis) spectroscopy techniques. After, doping of both S and Cl into ZnO no significant alteration in the nanorod morphology was noticed. The wurtzite crystal structure of ZnO was retained with a red shift in the 2Ɵ towards high angle. The XRD results are supported by the high-resolution transmission electron microscopy. The elemental analysis revealed a successful doping of S and Cl into ZnO structure. Importantly, the optical band gap of ZnO was decreased 2.9 eV upon doping of S and Cl ions. Thus, the nonmetal doping via S and Cl has significantly enhanced the photocatalytic properties of ZnO towards methylene blue (MB) due to high density of active sites and decreased charge recombination rate of electron-hole pairs. The photo-degradation efficiency towards MB reached 99.64% upon using S and Cl doped ZnO photocatalyst using optimum dose of 15 mg and initial dye concentration of 1.87 × 10−6 M. The use of simultaneous nonmetal doping concept could of great importance for the preparation of other nanostructured materials and their use in potential applications like solar cells, and photoelectrochemical water splitting.

A Comprehensive Review of Graphitic Carbon Nitride (g-C3N4)-Metal Oxide-Based Nanocomposites: Potential for Photocatalysis and Sensing.

g-C3N4 has drawn lots of attention due to its photocatalytic activity, low-cost and facile synthesis, and interesting layered structure. However, to improve some of the properties of g-C3N4, such as photochemical stability, electrical band structure, and to decrease charge recombination rate, and towards effective light-harvesting, g-C3N4–metal oxide-based heterojunctions have been introduced. In this review, we initially discussed the preparation, modification, and physical properties of the g-C3N4 and then, we discussed the combination of g-C3N4 with various metal oxides such as TiO2, ZnO, FeO, Fe2O3, Fe3O4, WO3, SnO, SnO2, etc. We summarized some of their characteristic properties of these heterojunctions, their optical features, photocatalytic performance, and electrical band edge positions. This review covers recent advances, including applications in water splitting, CO2 reduction, and photodegradation of organic pollutants, sensors, bacterial disinfection, and supercapacitors. We show that metal oxides can improve the efficiency of the bare g-C3N4 to make the composites suitable for a wide range of applications. Finally, this review provides some perspectives, limitations, and challenges in investigation of g-C3N4–metal-oxide-based heterojunctions.