Formation Of Heterostructures Research Articles

Photoelectrothermocatalytic reduction of CO2 to glycol via Cu2S/MoS2-Vs octahedral heterostructure with synergistic mechanism

The defects and interface engineering are efficient approaches to adjust the physical and chemical properties of nanomaterials to enhance catalytic performance. In this study, we report a new MOFs-driven porous Cu2S/MoS2-Vs octahedral semiconductor with heterostructure and photothermal effect. The introduction of sulfur vacancies directly improves the adsorption performance of CO2, and the formation of heterostructure significantly increases the charge transfer rate. The C-penetrating material obtained from MOFs not only acts as an octahedral skeleton support, but also gives photothermal effects under photoelectric conditions. The formation rate of sole C2 products in photoelectrocatalytic CO2 reduction by using Cu2S/MoS2-Vs heterostructure is up to 52 μM·h−1·cm−2 equal to the total electron transfer rate of 541 μM·h−1·cm−2. The carbene mechanism and reaction pathways were proposed and verified by 13CO2 isotopic labelling and operando Fourier transform infrared (FT-IR) spectra. The important intermediates of *CO2−, *CO, *CHO and *CHO-CHO were identified by operando FT-IR spectra. In the comparative experiments, the photothermal electrons are beneficial to C2 products. DFT calculations indicate that the presence of S vacancies (Vs) reduces the energy barrier for product generation.

Zn-assisted low-temperature reconstruction of NiCo heterogeneous catalysts for lithium-oxygen batteries

Developing catalysts with high catalytic activity and durability is an effective strategy for improving the electrochemical performance of lithium-oxygen batteries (LOBs). Metal atom doping and heterostructure construction have shown great potential in catalysis and are expected to be widely used in energy storage. In this study, a Zn-doped NiCo2O4/NiO heterostructured complex catalyst is designed and prepared as a cathode catalyst for LOBs. This metal-doped heterostructured complex catalyst, prepared at a lower annealing temperature, retains the most active sites. Additionally, the three-dimensional hollow structure of the catalyst not only facilitates mass transfer but also provides active sites through doping and heterostructure formation. The Zn-doped NiCo2O4/NiO catalyst exhibits excellent catalytic performance, resulting the generation of a silky Li2O2 discharge product film, and the higher adsorption energy for the intermediate product LiO2 also allows the discharge product to be tightly bound to the catalyst. The improved contact between the discharge products and the catalyst's active sites, along with the increased surface area, enhances charge transport and decomposition properties, leading to good reversibility of the LOB. Consequently, the LOB based on Zn-doped NiCo2O4/NiO heterostructure complex catalyst features high discharge capacity (12160 mAh/g at 200 mA g−1) and excellent durability (353 cycles, ∼1765 h). Furthermore, theoretical calculations show that the Zn-doped complex heterostructures have enhanced reaction kinetics of OER and ORR. This straightforward method of producing metal-doped heterostructured complex catalysts that induce uniform Li2O2 deposition valuable insights for enhancing the performance of LOBs.

Rational design of covalent organic frameworks/NaTaO3 S-scheme heterostructure for enhanced photocatalytic hydrogen evolution

As a typical perovskite material, NaTaO3 has been regarded as a potential catalyst for photocatalytic hydrogen evolution (PHE) process, due to its excellent photoelectric property and superior chemical stability. However, the photocatalytic activity of pure NaTaO3 was largely restricted by its poor visible-light absorption ability and rapid recombination of photogenerated charge carriers. Therefore, a covalently bonded TpBpy covalent organic framework (COF)/NaTaO3 (TpBpy/NaTaO3) heterostructure was designed and synthesized by the post modification strategy with (3-aminopropyl) triethoxysilane (APTES) and the in situ solvothermal process. Benefiting from the enhanced built-in electric field by the interfacial covalent bonds and the formation of S-scheme heterostructure between TpBpy and NaTaO3, which were proved by the Ar+-cluster depth profile and X-ray photoelectron spectroscopy (XPS), as well as density functional theory (DFT) calculation results, both the charge transfer efficiency and the PHE performance of the TpBpy/NaTaO3 composites were significantly improved. Additionally, the composites exhibited an excellent absorption performance in the visible region, which was also beneficial for the photocatalytic process. As expected, the optimal TpBpy/20%NaTaO3 composite achieved a remarkable hydrogen evolution rate of 17.3 mmol·g−1·h−1 (10 mg of catalyst) under simulated sunlight irradiation, which was about 173 and 2.4 times higher than that of pure NaTaO3 and TpBpy, respectively. This work provided a novel strategy for constructing highly effective and stable semiconductor/COFs heterostructures with strong interfacial interaction for photocatalytic hydrogen evolution.

ZnxFe3-xO4–ZnO heterojunction interfaced with poly(L-DOPA) electron transfer mediator layer for enhanced visible light photocatalytic activity

Z-scheme heterojunctions comprising ZnxFe3-xO4@poly(L-DOPA)@ZnO (ZF@PD@ZnO) were synthesized using solvothermal and precipitation techniques. The study aimed to investigate the impact of the poly(L-DOPA) electron transfer mediator on the photocatalytic performance of ZnxFe3-xO4@ZnO (ZF@ZnO) nanocomposites under visible light irradiation. X-ray diffraction (XRD) and HRTEM analysis confirmed the formation of heterostructures, identifying the crystalline phases of both ZnO and zinc ferrite. BFTEM images revealed a polyhedral shape for all samples, with a tendency toward mild agglomeration. The partial inversion of the zinc ferrite cubic spinel structure was evidenced by FT-IR, XPS, and VSM analyses. Zinc ferrite was found to be ferromagnetic, with cation distributions between tetrahedral (A) and octahedral (B) positions as [Zn0.62+Fe0.43+]A[Fe0.42+Fe1.63+]BO4. The samples exhibited notable photocatalytic activity against Rhodamine B, serving as a model contaminant. Furthermore, the stability and reusability of the samples were examined. Additionally, the study elucidated the photocatalytic mechanism produced by the ternary Z-scheme ZF@PD@ZnO, involving spin-polarized charge carriers. Energy band alignment was evaluated by combining ultraviolet photoelectron spectroscopy (UPS) with UV-Vis spectroscopy. The interplay between band alignment and reactive oxygen species (ROS) generation was discussed in correlation with EPR results. Enhanced ROS generation under visible light illumination, observed in the ZF@PD@ZnO nanocomposite, is mainly due to the addition of the conductive poly(L-DOPA) layer, acting as an electron transfer mediator in the Z-scheme heterojunction, ensuring enhanced charge separation.

Growth Processing and Strategies: A Way to Improve the Gas Sensing Performance of Nickel Oxide-Based Devices

The review paper provides a comprehensive analysis of nickel oxide (NiO) as an emerging material in environmental monitoring by surveying recent developments primarily within the last three years and reports the growth processing and strategies employed to enhance NiO sensing performance. It covers synthesis methods for pristine NiO, including vapor-phase, liquid-phase, and solution-processing techniques, highlighting advantages and limitations. The growth mechanisms of NiO nanostructures are explored, with a focus on the most recent research studies. Additionally, different strategies to improve the gas sensing performance of NiO are discussed (i.e., surface functionalization by metallic nanoparticles, heterostructure formation, carbon-based nanomaterials, and conducting polymers). The influence of these strategies on selectivity, sensitivity, response time, and stability of NiO-based sensors is thoroughly examined. Finally, the challenges and future directions that may lead to the successful development of highly efficient NiO-based gas sensors for environmental monitoring are introduced in this review.

Cu2O-based trifunctional catalyst for enhanced alkaline water splitting and hydrazine oxidation: Integrating sulfurization, Co incorporation, and LDH heterostructure

Developing an efficient electrocatalyst capable of working for multiple catalytic reactions in the same pH environment is a challenging task. In this work, we aimed to address this challenge by employing a systematic approach including sulfurization, Co incorporation, and heterostructure formation with layered double hydroxide (LDH) to unveil the potential of Cu2O for driving multiple catalytic reactions. The systematically modified Cu2O-electrocatalyst demonstrated remarkable efficiency in promoting the hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and hydrazine oxidation reaction (HzOR). The LDH-modified Cu2O_S_Co_CoFe sample exhibited an outstanding catalytic activity with low overpotentials of 280 mV for HER and 307 mV for OER at 100 mA cm−2 current density. The same sample also exhibited a remarkably reduced potential of only 0.343 V vs. RHE (VRHE) for HzOR at 100 mA cm−2 as compared to that of 1.53 VRHE for OER. Moreover, in a two-electrode setup for overall water splitting, the electrocatalyst achieved a significantly low cell voltage of 1.64 V to attain a current density of 20 mA cm−2 and further reduced to just 0.36 V during HzOR.

Synergy of Mo doping and heterostructures in FeCo2S4@Mo-NiCo LDH/NF as durable and corrosion-resistance bifunctional electrocatalyst towards seawater electrolysis at industrial current density

Electrolysis of seawater to produce hydrogen is a replenished way to utilize sustainable hydrogen energy. However, it remains a challenge to develop electrocatalysts with high chloride corrosion resistance and meet the industrial-required low overpotential at large current density. Here, a heterostructure FeCo2S4@Mo-NiCo LDH/NF (FCS@M-NC LDH/NF) catalyst consisting of Mo-doped NiCo LDH nanosheets on FeCo2S4 nanorods grown on nickel foam is demonstrated as a large-current–density electrocatalyst for seawater electrolysis. The hierarchical structure endows FCS@M-NC LDH/NF with abundant active sites and hydrophilic and aerophobic surfaces, which promotes the adsorption of OH− and accelerates gas-release capabilities during water electrolysis. Moreover, the incorporation of high-valence Mo species and the presence of heterostructures contribute to the outstanding corrosion resistance, selectivity, and activity of FCS@M-NC LDH/NF, which only requires 314 mV (HER) and 307 mV (OER) overpotential to achieve a large current density of 1000 mA cm−2 in alkaline electrolysis of seawater. Impressively, it maintains stable operation for 140 h at a current density of 500 mA cm−2 without the production of hypochlorite. Furthermore, density functional theory calculations demonstrate that Mo doping and formation of heterostructures decrease the adsorption energy barrier for intermediate on FCS@M-NC LDH/NF, which promotes electrocatalytic activity. The robust electronic interaction between FCS and M-NC LDH/NF promotes the redistribution of charges on the interface, boosting electrical conductivity and charge transfer in the FCS@M-NC LDH/NF. This study offers a mild way to create a bifunctional electrocatalyst with exceptional corrosion resistance and stability in industrial high-alkaline natural seawater electrolysis.

Construction of plasmonic CuS/attapulgite nanocomposites toward photothermal reforming of biomass for hydrogen production

As a naturally abundant resource, biomass holds significant potential as an alternative to non-renewable fossil feedstock for producing value-added chemicals and fuels. However, its applications are limited by low conversion efficiency and product selectivity. In this study, we synthesized plasmonic CuS/phosphoric acid-modified attapulgite (P-ATP) nanocomposites using a microwave hydrothermal approach. The formation of an S-type heterostructure between CuS and P-ATP markedly improved the separation of electrons and holes. Additionally, the CuS/P-ATP nanocomposites featured numerous acidic sites, significantly enhancing the conversion of 5-hydroxymethylfurfural (HMF) into furan-2,5-dicarbaldehyde (DFF). CuS-induced localized surface plasmon resonance (LSPR) extended the absorption spectrum into the near-infrared region, raising the surface temperature and substantially improving photocatalytic activity. The 30 % CuS/P-ATP exhibited the highest hydrogen evolution rate of 286 μmol g−1 h−1 and the highest DFF generation rate of 31 μmol g−1 h−1, while maintaining a 95 % selectivity for DFF. This study demonstrates the commercial potential of clay minerals for biomass valorization coupled with hydrogen production.

Phase-selective in-plane heteroepitaxial growth of H-phase CrSe2

Phase engineering of two-dimensional transition metal dichalcogenides (2D-TMDs) offers opportunities for exploring unique phase-specific properties and achieving new desired functionalities. Here, we report a phase-selective in-plane heteroepitaxial method to grow semiconducting H-phase CrSe2. The lattice-matched MoSe2 nanoribbons are utilized as the in-plane heteroepitaxial template to seed the growth of H-phase CrSe2 with the formation of MoSe2-CrSe2 heterostructures. Scanning tunneling microscopy and non-contact atomic force microscopy studies reveal the atomically sharp heterostructure interfaces and the characteristic defects of mirror twin boundaries emerging in the H-phase CrSe2 monolayers. The type-I straddling band alignments with band bending at the heterostructure interfaces are directly visualized with atomic precision. The mirror twin boundaries in the H-phase CrSe2 exhibit the Tomonaga-Luttinger liquid behavior in the confined one-dimensional electronic system. Our work provides a promising strategy for phase engineering of 2D TMDs, thereby promoting the property research and device applications of specific phases.

Construction of bayberry-like Cu2O/CuO and detection of trace Cl2 at low temperature

The effective detection of toxic and harmful gases is of great significance for protecting the environment and human health. The construction of heterostructures plays a crucial role in improving gas sensing performance of sensitive materials. In this study, an one-step solvothermal method was used to directly synthesize ∼2 μm bayberry-like Cu2O/CuO. Due to the formation of heterostructures, the gas sensing performance of the material is effectively improved. The optimal sensor based on Cu2O/CuO exhibits good gas sensing performance (S=45) to 10 ppm Cl2 at 50 ℃, with a detection limit as low as 300 ppb (S=1.33), good selectivity and reproducibility. Its excellent gas sensing performance can be attributed to the presence of oxygen vacancies in the material and the synergistic effect between Cu2O/CuO heterostructure components. The presence of oxygen vacancies increases the adsorption of oxygen ions on the material surface. The formation of heterostructures not only regulates the electronic structure of CuO, but also provides more adsorption sites for the target gas. Therefore, the bayberry-like Cu2O/CuO material can be used as a candidate sensitive material for low-temperature Cl2 gas detection.

Diethanolamine-functionalized BiOI hollow microspheres with negative conduction bands maximize the visible light photocatalytic performance for CO2 reduction

Bismuth iodide oxides have a wide range of applications as visible light photocatalysts in CO2 reduction reactions. While formation of heterostructures between semiconductors has been actively used to enhance catalytic reduction performance, the functional groups used to improve the separation ability of electron/holes (e-/h+) and surface energy band positions of BiOI surfaces have been rarely mentioned. Here, a new modification strategy was reported to improve the photocatalytic performance using solvents with hydroxyl functional groups to change the surface structure of BiOI hollow microspheres. Intriguingly, the BiOI hollow microspheres functionalized using diethanolamine have a larger negative surface conduction band than BiOI. Thus the photogenerated electron reduction capacity of the diethanolamine-functionalized BiOI is greatly enhanced, which can be obtained from the yield of reduction reaction testing and characterization results. This hydroxyl functional group modified BIOI provides a new strategy for improving photocatalytic performance. The DFT simulation provides a theoretical basis for photocatalytic CO2 reduction.

Interfacial Electron Transfer in PbI2@Single-Walled Carbon Nanotube van der Waals Heterostructures for High-Stability Self-Powered Photodetectors.

Acquiring a deep insight into the electron transfer mechanism and applications of one-dimensional (1D) van der Waals heterostructures (vdWHs) has always been a significant challenge. Herein, through direct observation using aberration-corrected transmission electron microscopy (AC-TEM), we verify the stable formation of a high-quality 1D heterostructure composed of PbI2@single-walled carbon nanotubes (SWCNTs). The phenomenon of electron transfer between PbI2 and SWCNT is elucidated through spectroscopic investigations, including Raman and X-ray photoelectron spectroscopy (XPS). Electrochemical testing indicates the electron transfer and enduring stability of 1D PbI2 within SWCNTs. Moreover, leveraging the aforementioned electron transfer mechanism, we engineer self-powered photodetectors that exhibit exceptional photocurrent and a 3-order-of-magnitude switching ratio. Subsequently, we reveal its unique electron transfer behavior using Kelvin probe force microscopic (KPFM) tests. According to KPFM, the average surface potential of SWCNTs decreases by 80.6 mV after filling. Theoretical calculations illustrate a charge transfer of 0.02 e per unit cell. This work provides an effective strategy for the in-depth investigation and application of electron transfer in 1D vdWHs.

Construction of nickel phosphide/iron oxyhydroxide heterostructure nanoparticles for oxygen evolution

Active and stable oxygen evolution electrocatalysts are essential in increasing the efficiency of water electrolyzers. The Ni2P/Fe(O)OH heterostructure nanoparticles are prepared via solvothermal phosphidization of Ni metal-organic frameworks (MOF) followed by immersing in Fe3+ aqueous solution. Characterizations reveal that the Ni2P/Fe(O)OH heterostructure nanoparticles are 12.83 nm in size averagely, and the heterointerface induces electron interactions between the Ni2P and Fe(O)OH phases. When used to catalyze OER in alkaline solutions, the Ni2P/Fe(O)OH-40/nickel foam (NF) is the most active and exhibits 240 mV overpotential to reach 10 mA cm−2 oxygen evolution (OER) current densities, which is significantly better than the Ni2P/NF. Lower apparent activation energy, charge transfer resistance, and Tafel slope, along with higher electron rate constant are observed at Ni2P/Fe(O)OH-40/NF, which suggests that the OER kinetics is more facile at the surface of heterostructure nanoparticles. The OER mechanistic pathways of both Ni2P/Fe(O)OH-40/NF and Ni2P/NF involve decoupled electron and proton transfer processes, and higher degree of lattice oxygen oxidation mechanism (LOM) participation is observed at Ni2P/Fe(O)OH-40/NF, which results from the increased acidity of the Ni sites. Density functional theory calculations prove that the formation of heterostructure with Fe(O)OH alters the band structure and the adsorption energies of OER intermediates, which leads to lower energy barrier in the rate-determining step. The Ni2P/Fe(O)OH-40/NF is also stable towards OER in alkaline solutions.

PdSe2/MoSe2: a promising van der Waals heterostructure for field effect transistor application

The field-effect transistor (FET) is a fundamental component of semiconductors and the electronic industry. High on-current and mobility with layer-dependent features are required for outstanding FET channel material. Two-dimensional materials are advantageous over bulk materials owing to their higher mobility, high ON/OFF ratio, low tunneling current, and leakage problems. Moreover, two-dimensional heterostructures provide a better way to tune electrical properties. In this work, the two distinct possibilities of PdSe2/MoSe2 heterostructure have been employed through mechanical exfoliation and analyzed their electrical response. These diffe approaches to heterostructure formation serve as crucial components of our investigation, allowing us to explore and evaluate the unique electronic properties arising from each design. This work demonstrates that the heterostructure possesses a better ON/OFF ratio of ∼5.78 × 105, essential in switching characteristics. Moreover, MoSe2 provides a defect-free interface to PdSe2, resulting in a higher ON current of ∼10 μA and mobility of ∼63.7 cm2V−1s−1, necessary for transistor applications. In addition, comprehending the process of charge transfer occurring at the interface between transition metal dichalcogenides is fundamental for advancing next-generation technologies. This work provides insights into the interface formed between the PdSe2 and MoSe2 that can be harnessed in transistor applications.

Sulfur Vacancy Related Optical Transitions in Graded Alloys of MoxW1‐xS2 Monolayers

AbstractEngineering electronic bandgaps is crucial for applications in information technology, sensing, and renewable energy. Transition metal dichalcogenides (TMDCs) offer a versatile platform for bandgap modulation through alloying, doping, and heterostructure formation. Here, the synthesis of a 2D MoxW1‐xS2 graded alloy is reported, featuring a Mo‐rich center that transitions to W‐rich edges, achieving a tunable bandgap of 1.85 to 1.95 eV when moving from the center to the edge of the flake. Aberration‐corrected high‐angle annular dark‐field scanning transmission electron microscopy showed the presence of sulfur monovacancy, VS, whose concentration varied across the graded MoxW1‐xS2 layer as a function of Mo content with the highest value in the Mo‐rich center region. Optical spectroscopy measurements supported by ab initio calculations reveal a doublet electronic state of VS, which is split due to the spin‐orbit interaction, with energy levels close to the conduction band or deep in the bandgap depending on whether the vacancy is surrounded by W atoms or Mo atoms. This unique electronic configuration of VS in the alloy gave rise to four spin‐allowed optical transitions between the VS levels and the valence bands. The study demonstrates the potential of defect and optical engineering in 2D monolayers for advanced device applications.

All-carbon heterostructures self-assembly during field electron emission from diamond nanotip

In this study we demonstrate formation of all-carbon heterostructures induced by field electron emission from diamond needle-shaped crystallites with nanoscale tips. We show that at certain experimental conditions a carbon nanoprotrusion can be formed at the apex of a diamond emitter. Staircase-like current-voltage curves observed for such emitters indicated the presence of the Coulomb blockade effect in the self-assembled all-carbon heterostructures. The mechanism of nanoprotrusion formation via the field-induced surface diffusion of carbon atoms is revealed by observing the structural transformation of the emitter material using transmission electron microscopy. We also explore how the properties of the formed heterostructures evolve with the field emission current, and show that the characteristic size of the formed nanoprotrusion depends on the dimensions of the diamond nanotip. The developed approach offers a way to reproducible fabrication of heterostructured emitters which can be applied as coherent single-electron sources in vacuum nanoelectronics and electron quantum optics.

Tunable electronic properties and optoelectronic characteristics of MoGe2N4/SiC van der Waals heterostructure

The assembly of van der Waals (vdW) heterostructure with easily regulated electronic properties provides a new way for the expansion of two-dimensional materials and promotes the development of optoelectronics, sensors, switching devices and other fields. In this work, a systematic investigation of the electronic properties of MoGe2N4/SiC heterostructures using density functional theory has been conducted, along with the modulation of electronic properties by vertical strain and the potential application prospects in optoelectronic devices. The results show that MoGe2N4/SiC heterostructure has excellent dynamic and thermal stability and belongs to type-II band alignment semiconductors. This is extremely beneficial for the separation of photo-generating electron-hole pairs, so it has important significance for the development of photovoltaic materials. In addition, under the control of vertical strain, the semiconductor-metal transition occurs in the MoGe2N4/SiC heterostructure when the compressive strain reaches 6%. In the case of compressive strain less than 6% and tensile strain, the MoGe2N4/SiC heterostructure maintains the type-II band alignment semiconductor characteristics. Meanwhile, we find that the MoGe2N4/SiC heterostructure has optical absorption coefficients of up to 105 in the visible and ultraviolet light ranges, which can improve the absorption coefficients of the MoGe2N4 and SiC monolayer in some visible light regions. Finally, the optical conductivity of the MoGe2N4/SiC heterostructure exhibits significant anisotropy, with the armchair direction displaying higher conductivity within the orange light range. In conclusion, the formation of vdW heterostructure by vertically stacking MoGe2N4 and SiC monolayers can effectively improve their electronic and optical properties, which provides a valuable reference for the future development of electronic devices and photovoltaic materials.

Langmuir-Blodgett organic films deposition for the formation of conformal 2D inorganic-organic heterostructures

2D inorganic materials offer the opportunity to design and build heterostructures with unprecedented atomic control down to a monolayer. Integrating inorganic 2D layered materials, with the unlimited variety of organic molecules, provides a good platform for basic research and the formation of functional 2D organic-inorganic heterostructures, with tailored optoelectronic properties. In this work, we propose to employ a Langmuir-Blodgett (LB) monolayer deposition technique for the large-scale assembly of 2D inorganic-organic heterostructures. First, the transition-metal dichalcogenidemonolayers (TMDCs), MoS2 and WSe2, are grown by a chemical vapor deposition (CVD)-based method. This is followed by the LB deposition of a monolayer(s) of Zn(II)-5-(4-aminophenyl)-10,15,20-(triphenyl)porphyrin (Zn-TPP(1f)). The morphology, optical and electrical properties were systematically studied for the two TMDC systems. Despite the similarities between both TMDCs, their heterostructures with Zn-TPP(1f) monolayers show a very different optical response; a strong quenching of the photoluminescence intensity is measured for the Zn-TPP(1f)/MoS2 system, an opposite trend, PL enhancement, is obtained for the WSe2 based heterostructure. These results are explained by the differences within their electronic band diagrams, as elucidated using a wide variety of spectroscopic methodologies. The orthogonal impact on the PL emission may serve as a general platform for the formation of 2D organic-inorganic heterostructures, with controlled optical properties.

Tuning the Activity and Stability of CoCr-LDH by Forming a Heterostructure on Surface-Oxidized Nickel Foam for Enhanced Water-Splitting Performance.

The development of low-cost, efficient catalysts for electrocatalytic water splitting to generate green hydrogen is a hot topic among researchers. Herein, we have developed a highly efficient heterostructure of CoCr-LDH on NiO on nickel foam (NF) for the first time. The preparation strategy follows the simple annealing of a cleaned NF without using any Ni salt precursor, followed by the growth of CoCr-LDH nanosheets over the surface-oxidized NF. The CoCr-LDH/NiO/NF catalyst shows excellent electrocatalytic activity and stability toward oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in a 1 M KOH solution. For OER, only 253 mV and for HER, only 185 mV overpotentials are required to attain a 50 mA cm-2 current density. Also, the long-term stability of both the OER and HER for 60 h proves its robustness. The turnover frequency value for the OER increased 1.85 times after the heterostructure formation compared to bare CoCr-LDH. The calculated Faradaic efficiency values of 97.4 and 94.75% for the OER and HER revealed the high intrinsic activity of the heterostructure. Moreover, the heterostructure only needs 1.57 V of cell voltage when acting as both the anode and the cathode to achieve a 10 mA cm-2 current density. The long-term stability of 60 h for the total water-splitting process proves its excellent performance. Several systematic pre- and post-experiment characterizations prove its durable nature. These excellent OER and HER activities and stabilities are attributed to the surface-modified electronic structure and thin nanosheet-like surface morphology of the heterostructure. The thin, wide, and modified surface of the catalyst facilitates the diffusion of ions (reactants) and gas molecules (products) at the electrode/electrolyte interface. Furthermore, electron transfer from n-type CoCr-LDH to p-type NiO results in enhanced electronic conductivity. This study demonstates the effective design of a self-supported heterostructure with minimal synthetic steps to generate a bifunctional electrocatalyst for water splitting, contributing to the greater cause of green hydrogen economy.

Heterostructure of TiO2 and SnS for enhancing the structural, optical and photovoltaic properties of solar cells

In this article a novel heterostructure of TiO2@SnS has been prepared by sol-gel technique for increase the current density and performance of solar cells. The main objective of this study is to prepare efficient solar cell materials with a simple chemical technique. XRD confirmed orthorhombic structure of SnS and tetragonal structure of TiO2 Raman analysis confirm the formation of heterostructure. Heterostructure TiO2@SnS showed large grain size (38 nm), small d-spacing (3.50 Å), and low value of Eg (2.7 eV). Photoluminesence show that peaks are shifted due to heterostructures and defects are remove. These materials' solar cells are created using the configuration glass/FTO/TiO2/SnS/P3HT/Au. TiO2@SnS based solar cell has high values of open circuit voltage (0.66 V), short circuit current density (4.57 mA cm−2), fill factor (0.79), and efficiency η (2.37 %). These findings reveals that heterostructure of TiO2@SnS could be a promising materials for improving the efficiency of solar cells.