Heterojunction Arrays Research Articles

Construction and performance of novel organic/inorganic p-n heterojunction array photoelectrodes for light-assisted seawater batteries

Construction and performance of novel organic/inorganic p-n heterojunction array photoelectrodes for light-assisted seawater batteries

Investigation of a visible-light-driven molecularly imprinted photoelectrochemical sensing platform for ultrasensitive and selective detection of diflubenzuron utilizing an in-situ grown 3D hierarchical structure

An ultrasensitive molecularly imprinted polymer-photoelectrochemical (MIP-PEC) sensing platform has been successfully fabricated for the detection of diflubenzuron (DBZ) under visible-light irradiation. The noval photoactive material was a ternary Bi2S3/BiVO4/TiO2 nanotube arrays (BVT) heterojunction, grown in-situ on a Ti substrate. The distinct architecture of BVT featured BiVO4 nanoparticles anchored onto TiO2 nanotube arrays and wrapped by Bi2S3 nanofibers. This innovative design, coupled with the aligned energy bands of BVT, significantly boosted visible-light absorption, and photo-induced charge separation and transfer, leading to an enhanced photocurrent response surpassing that of binary and single-component systems. The sensing platform displayed remarkable sensitivity and a broad detection range for DBZ with a linear range of 0.01–1000 ng mL−1 and a limit of detection of 1.25 pg mL−1. Its selectivity was further validated by comparable photocurrent responses in the presence of interfering substances, highlighting its accuracy in detecting DBZ in complex matrices. Additionally, the sensing platform demonstrated excellent stability and reproducibility, ensuring reliable results over multiple measurements. Evaluation of the sensing platform in real samples, including tap water and apples, has confirmed its high accuracy with recovery rates between 94.4 % and 103.4 %. Therefore, this visible-light-driven MIP-PEC sensing platform exhibits considerable potential for application in ultrasensitive detection of DBZ. This work offers novel insights into the in-situ preparation of high-performance sensors for applications in food safety and environmental monitoring.

Strong Covalent Coupling in Vertically Layered SnSe2/PTAA Heterojunctions Enabled High Performance Inorganic-Organic Hybrid Photodetectors.

Controllable large-scale integration of two-dimensional (2D) materials with organic semiconductors and the realization of strong coupling between them still remain challenging. Herein, we demonstrate a wafer-scale, vertically layered SnSe2/PTAA heterojunction array with high light-trapping ability via a low-temperature molecular beam epitaxy method and a facile spin-coating process. Conductive probe atomic force microscopy (CP-AFM) measurements reveal strong rectification and photoresponse behavior in the individual SnSe2 nanosheet/PTAA heterojunction. Theoretical analysis demonstrates that vertically layered SnSe2/PTAA heterojunctions exhibit stronger C-Se covalent coupling than that of the conventional tiled type, which could facilitate more efficient charge transfer. Benefiting from these advantages, the SnSe2/PTAA heterojunction photodetectors with an optimized PTAA concentration show high performance, including a responsivity of 41.02 A/W, an external quantum efficiency of 1.31 × 104%, and high uniformity. The proposed approach for constructing large-scale 2D inorganic-organic heterostructures represents an effective route to fabricate high-performance broadband photodetectors for integrated optoelectronic systems.

Unique sandwich-cookie-like nanosheet array heterojunction bifunctional electrocatalyst towards efficient overall water/seawater splitting

Construction of multi-component heterostructures is an effective strategy for electrocatalysts to improve both the hydrogen evolution reaction (HER) at the cathode and the oxygen evolution reaction (OER) activity at the anode. Herein, an efficient bifunctional electrocatalyst towards overall water/seawater splitting (OW/SS) is reported with strategy of heterostructure construction (ruthenium/nickel phosphorus) on nickel hydroxide (Ni(OH)2). With the unique hydrolysis layer (Ni(OH)2), the processes of H2O hydrolysis and the adsorption/desorption of H*/O-containing intermediates (OH, O, OOH) were greatly boosted by Ru and P sites, which acted as the catalytic active centers of OER and HER, respectively. In addition, the electronic structure reconfiguration was realized through the strong interaction between multi-interfaces. For alkaline HER at the current density of 10 mA cm−2, the overpotential of Ru-P-Ni(OH)2/NF (denoted as RNPOH/NF) was 98 mV, whereas just 230 mV of overpotential was essential to stimulate alkaline OER at the current density of 20 mA cm−2. Specifically, as a bifunctional electrocatalyst towards overall water splitting, RNPOH/NF deserves cell voltages of 1.7/1.92 V and 1.75/1.94 V, respectively, to activate current densities of 50/100 mA cm−2 in alkaline water/seawater systems, together with a good durability of 12 h. This work contributes insights to the development of bifunctional electrocatalysts for overall water/seawater splitting.

Ternary BiOI/Bi2S3/Au Nanosheet Arrays as a Photoelectrochemical Signal Converter for the Detection of Cardiac Troponin I.

Nanosheet arrays with stable signal output have become promising photoactive materials for photoelectrochemical (PEC) immunosensors. However, an essential concern is the facile recombination of carriers in one-component nanoarrays, which cannot be readily prevented, ultimately resulting in weak photocurrent signals. In this study, an immunosensor using gold nanoparticle-anchored BiOI/Bi2S3 nanosheet arrays (BiOI/Bi2S3/Au) as a signal converter was fabricated for sensitive detection of cardiac troponin I (cTnI). The ternary nanosheet arrays were prepared by a simple method in which Bi2S3 was well-coated on the BiOI surface by in situ growth, whereas the addition of Au further improved the photoelectric conversion efficiency and could link more antibodies. The three-dimensional (3D) ordered sheet-like network array structure and BiOI/Bi2S3/Au ternary nanosheet arrays showed stable and high photoelectric signal output and no significant difference in signals across different batches under visible light excitation. The fabricated immunosensor has a sensitive response to the target detection marker cTnI in a wide linear range of 500 fg/mL to 50 ng/mL, and the detection limit was 32 fg/mL, demonstrating good stability and selectivity. This work not only shows the great application potential of ternary heterojunction arrays in the field of PEC immunosensors but also provides a useful exploration for improving the stability of immunosensors.

Construction of Cobalt Porphyrin-Modified Cu2O Nanowire Array as a Tandem Electrocatalyst for Enhanced CO2 Reduction to C2 Products.

Here, the molecule-modified Cu-based array is first constructed as the self-supporting tandem catalyst for electrocatalytic CO2 reduction reaction (CO2RR) to C2 products. The modification of cuprous oxide nanowire array on copper mesh (Cu2O@CM) with cobalt(II) tetraphenylporphyrin (CoTPP) molecules is achieved via a simple liquid phase method. The systematical characterizations confirm that the formation of axial coordinated Co-O-Cu bond between Cu2O and CoTPP can significantly promote the dispersion of CoTPP molecules on Cu2O and the electrical properties of CoTPP-Cu2O@CM heterojunction array. Consequently, as compared to Cu2O@CM array, the optimized CoTPP-Cu2O@CM sample as electrocatalyst can realize the 2.08-fold C2 Faraday efficiency (73.2%vs 35.2%) and the 2.54-fold current density (‒52.9vs ‒20.8mAcm-2) at ‒1.1V versus RHE in an H-cell. The comprehensive performance is superior to most of the reported Cu-based materials in the H-cell. Further study reveals that the CoTPP adsorption on Cu2O can restrain the hydrogen evolution reaction, improve the coverage of *CO intermediate, and maintain the existence of Cu(I) at low potential.

Efficient WO3 Nanoplate Arrays Photoanode Modified by ZnO Nanosheets for Enhanced Charge Separation and Transfer to Promote Photoelectrochemical Performances

AbstractA key factor in the photoelectrochemical (PEC) performance of photoelectrodes is the efficient separation and transfer of photogenerated charges. Herein, a novel photoanode comprising three‐dimensional (3D) WO3 nanoplate@ZnO nanosheet hierarchical type‐II heterojunction arrays (3D WO3@ZnO HHAs) is designed and constructed via modification of the WO3 nanoplate arrays with ZnO nanosheets. The synthesized materials are characterized viaX‐ray diffraction (XRD), ultraviolet and visible spectrophotometry (UV–vis), scanning electon microscopy (SEM), transmission electron microscopy (TEM), and X‐ray photoelectron spectroscopy (XPS) analyses. Photoelectrochemical (PEC) test results reveal that the synthesized 3D WO3@ZnO HHAs photoanode exhibits reduced charge transfer resistance, improved electron‐hole pair life, and enhanced photocurrent density (≈4.5 times increase in comparison to that of the bare WO3). The increased light capture and high surface area in contact with the electrolyte as well as the enhanced charge transfer through the synergy between morphology and band structures may be responsible for the improved PEC characteristics.

2D Lateral Heterojunction Arrays with Tailored Interface Band Bending.

Two-dimensional (2D) lateral heterojunction arrays, characterized by well-defined electronic interfaces, hold significant promise for advancing next-generation electronic devices. Despite this potential, the efficient synthesis of high-density lateral heterojunctions with tunable interfacial band alignment remains a challenging. Here, a novel strategy is reported for the fabrication of lateral heterojunction arrays between monolayer Si2Te2 grown on Sb2Te3 (ML-Si2Te2@Sb2Te3) and one-quintuple-layer Sb2Te3 grown on monolayer Si2Te2 (1QL-Sb2Te3@ML-Si2Te2) on a p-doped Sb2Te3 substrate. The site-specific formation of numerous periodically arranged 2D ML-Si2Te2@Sb2Te3/1QL-Sb2Te3@ML-Si2Te2 lateral heterojunctions is realized solely through three epitaxial growth steps of thick-Sb2Te3, ML-Si2Te2, and 1QL-Sb2Te3 films, sequentially. More importantly, the precisely engineering of the interfacial band alignment is realized, by manipulating the substrate's p-doping effect with lateral spatial dependency, on each ML-Si2Te2@Sb2Te3/1QL-Sb2Te3@ML-Si2Te2 junction. Atomically sharp interfaces of the junctions with continuous lattices are observed by scanning tunneling microscopy. Scanning tunneling spectroscopy measurements directly reveal the tailored type-II band bending at the interface. This reported strategy opens avenues for advancing lateral epitaxy technology, facilitating practical applications of 2D in-plane heterojunctions.

Interfacial Electronic Modulation of Mo5N6/Ni3S2 Heterojunction Array Boosts Electrocatalytic Alkaline Overall Water Splitting.

Bifunctional electrocatalysts with excellent activity and durability are highly desirable for alkaline overall water splitting, yet remain a significant challenge. In this contribution, palm-like Mo5N6/Ni3S2 heterojunction arrays anchored in conductive Ni foam (denoted as Mo5N6-Ni3S2 HNPs/NF) are developed. Benefiting from the optimized electronic structure configuration, hierarchical branched structure and abundant heterogeneous interfaces, the as-synthesized Mo5N6-Ni3S2 HNPs/NF electrode exhibits remarkably stable bifunctional electrocatalytic activity in 1m KOH solution. It only requires ultralow overpotentials of 59 and 190mV to deliver a current density of 10mAcm-2 for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in 1m KOH solution, respectively. Importantly, the overall water splitting electrolyzer assembled by Mo5N6-Ni3S2 HNPs/NF exhibits an exceptionally low cell voltage (1.48V@10mAcm-2) and outstanding durability, surpassing most of the reported Ni-based bifunctional materials. Density functional theory (DFT) further confirms the heterostructure can optimize the Gibbs free energies of H and O-containing intermediates (OH, O, OOH) during HER and OER processes, thereby accelerating the catalytic kinetics of electrochemical water splitting. The findings provide a new design strategy toward low-cost and excellent catalysts for overall water splitting.

Optical Microlithography of Perovskite Quantum Dots/Organic Semiconductor Heterojunctions for Neuromorphic Photosensors

AbstractHeterojunctions of perovskite quantum dots (QDs) and organic semiconductors (OSCs) can synergistically leverage the unique optoelectronic properties of different functional components to fabricate advanced optoelectronic devices, such as neuromorphic photosensors, by low‐cost solution processes. However, a long‐lasting challenge remains in micropatterning high‐density perovskite QDs/polymer OSCs heterojunction array with high yield and reliability due to the fragility of functional layers to organic solvents. High‐density and micro‐structure patterned organic neuromorphic photosensor arrays based on OSCs and QDs are thus rarely reported. Here, an effective cross‐linking microlithography strategy is reported to fabricate perovskite QDs/OSCs microstructure arrays. The fabricated CsPbBr3 QDs/(poly(2,5‐(2‐octyldodecyl)−3,6‐diketopyrrolopyrrole‐alt‐5,5‐(2,5‐di(thien‐2‐yl) thieno [3,2‐b] thiophene) (DPPDTT) planer heterojunctions phototransistor array presents minor device‐to‐device variation, high density (6500 devices cm−2), and high yield (almost 100%). The device array exhibits impressive merits as a neuromorphic photosensor, including a photosensitivity of 3.02 × 107, a responsivity up to 1.92 × 104 A W−1, a detectivity exceeding 1014 Jones, and a persistent photoconductivity. Moreover, an energy consumption as low as 27.9 aJ is achieved at an operating voltage of −0.0001 V. The potential application of the heterojunction neuromorphic photosensor array in motion perception is demonstrated in conjunction with a neural network.

Preparation of Surface Dispersed WO3/BiVO4 Heterojunction Arrays and Their Photoelectrochemical Performance for Water Splitting.

In this work, a surface dispersed heterojunction of BiVO4-nanoparticle@WO3-nanoflake was successfully prepared by hydrothermal combined with solvothermal method. We optimized the morphology of the WO3 nanoflakes and BiVO4 nanoparticles by controlling the synthesis conditions to get the uniform BiVO4 loaded on the surface of WO3 arrays. The phase composition and morphology evolution with different reaction precursors were investigated in detail. When used as photoanodes, the WO3/BiVO4 composite exhibits superior activity with photocurrent at 3.53 mA cm-2 for photoelectrochemical (PEC) water oxidation, which is twice that of pure WO3 photoanode. The superior surface dispersion structure of the BiVO4-nanoparticle@WO3-nanoflake heterojunction ensures a large effective heterojunction area and relieves the interfacial hole accumulation at the same time, which contributes to the improved photocurrents together with the stability of the WO3/BiVO4 photoanodes.

Piezopotential and vacancies co-enhanced sonodynamic response of a ZnO-TiO2-x heterojunction array for osteointegration in MRSA-infected osteomyelitis

Preventing multidrug-resistant bacteria-related osteomyelitis and simultaneously improving osseointegration are in great demand for orthopedic implants. Herein, an ultrasound (US)-responsive array of nanorod-like core–shell heterojunctions is developed on Ti substrate, in which oxygen vacancies (OVs) and residual compressive stresses are respectively introduced into TiO2 shells and ZnO cores via annealing in argon and ice cooling. The OVs narrow TiO2 band gap to enhance the formation of US-excited electron-hole pairs, while the ZnO-generated piezoelectric field by the residual compressive stress efficiently separates these electron-hole pairs. The combination of these two effects in the array leads to much more generation of reactive oxygen species than either under US irradiation, in which the piezoelectric field-derived separation of electron-hole pairs plays a crucial role. Consequently, the array exhibits high bacteria-killing and biofilm-eradicating efficacy of methicillin-resistant Staphylococcus aureus (MRSA), possessing strong osseointegration in MRSA-infected osteomyelitis of rat.

Flexible, self-powered, and polarization-sensitive photodetector based on perovskite lateral heterojunction microwire arrays

The fabrication of different perovskite materials with superior properties into lateral heterostructures can greatly improve device performance and polarization sensitivity. However, the sensitivity of perovskites to solvents and environmental factors makes the fabrication of lateral heterojunctions difficult. Here, we realize high-quality perovskite microwire crystal heterojunction arrays using regioselective ion exchange. Photodetectors with responsivity and detectivity up to 748 A W−1 and 8.2×1012 Jones are fabricated. The photodetector exhibits responsivity as high as 13.5 A W−1 at 0 V bias. In addition, the device exhibits ultra-high polarization sensitivity with a dichroic ratio of 5.6, and 81% of its performance was maintained after 144 days of exposure to air.

Effects of TiO2 thin films on silicon nanowire arrays in heterojunction solar cells

In recent years, the energy crisis has gained increasing attention, with greater emphasis being placed on renewable energy. Currently, solar power is regarded as the most developed form of renewable energy. Many materials have been used in solar cells. Radiofrequency (RF) magnetron sputtering is an effective technique used to produce large-area, easy-to-process thin films. In this study, we fabricated p-layer silicon nanowire (SiNW) arrays by using electroless etching to replace previous multilayer films. TiO2-SiNW array heterojunctions were fabricated by preparing TiO2 as an N layer through magnetron sputtering. Subsequently, the Grey–Taguchi method was used to analyze and optimize p–n heterojunctions with TiO2 films. After the effects of the sputtering parameters (RF power, process pressure, deposition temperature, and deposition time) on surface morphology, material structure, photoelectric conversion efficiency, and reflectivity were investigated, an aluminum-doped zinc oxide (AZO) window layer was added and annealed. Grey correlation analysis revealed a decrease in reflectivity from 8.02225 % to 7.72081 % and an increase in photoelectric conversion efficiency from 0.01915 % to 0.082 %. During the confirmation runs, the TiO2 film was found to be amorphous and wrapped around an array of SiNWs. After the AZO window layer was added, reflectivity increased to 18.04712 %, and the efficiency of photoelectric conversion increased to 0.124 %. In addition, according to the results of the confirmation runs, the AZO film was polymorphic. These experimental results confirm the effectiveness of RF magnetron sputtering, which provides high reflectivity and photoelectric conversion efficiency.

Dual-mode Conversion of Photodetector And Neuromorphic Vision Sensor via Bias Voltage Regulation on A Single Device.

For optoelectronic devices that convert optical signal to electrical signal, they can have a fast photoresponse speed to function as a photodetector, or possess the ability to perceive, memorize and process images to act as a neuromorphic vision sensor (NVS). However, the simultaneous implementation of photodetector and NVS on a single device faces a great challenge, due to the contradiction of photoresponse speed. In this work, to simultaneous achieve this complex function in a single device, trench-bridged GaN/Ga2 O3 /GaN back-to-back double heterojunction array device is fabricated. Interestingly, the device shows fast photoresponse and persistent photoconductivity behavior at low and high voltages, respectively, through the modulation of oxygen vacancy ionization and de-ionization processes in Ga2 O3 . Consequently, the role of the optoelectronic device can be altered between photodetector and NVS by simply adjusting the bias voltage. As a photodetector, the device is able to realize fast optical imaging and optical communication functions. On the other hand, the device exhibits outstanding image sensing, image memory, and neuromorphic visual pre-processing as a NVS. The utilization of NVS for image pre-processing leads to a noticeable enhancement in both the recognition accuracy and efficiency. The results presented in this work not only offer a new avenue to obtain complex functionality on a single optoelectronic device, but also provide the opportunities to implement advanced robotic vision systems and neuromorphic computing. This article is protected by copyright. All rights reserved.

Interface-induced enhancement of paired electrolysis in 5-hydroxymethylfurfural-H2O system on symbiotic nickel/molybdenum nitride heterostructure

Pairing the hydrogen evolution reaction (HER) with the thermodynamics-friendly electrooxidation reaction (EOR) is a powerful way to maximize the energy/economic effectiveness, but still a challenge. Herein, the symbiotic Ni/MoN heterojunction arrays were constructed on foam (Ni/MoN/NF) by the nitridation-induced in situ reduction/conversion strategy. The fascinating interfacial electronic structure and surface reconstruction of Ni/MoN/NF heterojunction are responsible for the enhanced HMF-H2O paired electrolysis. Ni/MoN/NF only requires a low overpotential of 53 mV to reach the HER current density of 10 mA cm−2, as well as the good durability; and NiOOH derived on the anode are electronically activated by MoN to achieving high-efficiency conversion from HMF to FDCA (∼100 % conversion, 97.5 % yield and 97.4 % Faradaic efficiency). For the HMF-H2O paired electrolysis, the assembled Ni/MoN/NF||Ni/MoN/NF electrolyzer only requires a low potential of 1.391 V to yield the current density of 10 mA cm−2, ranking at the forefront in the reported coupling catalysts. Theoretical calculations manifest that the upshift of d-band center of the NiOOH/MoN heterojunction contributes to HMF chemisorption and activation, thereby enhancing its catalytic activity towards HMFEOR. Our study sheds light on the significance of designing the paired electrolysis with low voltage input for renewable energy applications.

Preparation and application of Au nanoparticles modified p-CuO/n-ZnO heterojunction arrays for promoting photoelectrochemical water splitting

Preparation and application of Au nanoparticles modified p-CuO/n-ZnO heterojunction arrays for promoting photoelectrochemical water splitting

Novel trifunctional electrocatalyst of nickel foam supported Co2P/NiMoO4 heterostructures for overall water splitting and urea oxidation

The process of electrocatalytic water splitting for hydrogen generation is significantly limited by sluggish kinetics of the anodic oxygen evolution reaction (OER). The efficiency of H2 electrocatalytic generation can be improved by reducing the anode potential or substituting urea oxidation reaction (UOR) for oxygen evolution process. Here, we report a robust catalyst based on Co2P/NiMoO4 heterojunction arrays supported on nickel foam (NF) for water splitting and urea oxidation. In the hydrogen evolution reaction in alkaline media, the optimized catalyst Co2P/NiMoO4/NF displayed a lower overpotential (169 mV) at a large current density (150 mA cm−2) compared to 20 wt% Pt/C/NF (295 mV@150 mA cm−2). In the OER and UOR, the potentials were as low as 1.45 and 1.34 V. These values surpass (for OER), or compare favorably to (for UOR), the most advanced commercial catalyst RuO2/NF (at 10 mA cm−2). This outstanding performance was attributed to the addition of Co2P, which has a significant effect on the chemical environment and electron structure of NiMoO4, while increasing the number of active sites and promoting charge transfer across the Co2P/NiMoO4 interface. This work proposes a high-performance and cost-effective electrocatalyst for water splitting and urea oxidation.

0D/1D CuFeO2/CuO nanowire heterojunction arrays for improved photoelectrocatalytic reduction of CO2 to ethanol

CuO material with a bandgap of 1.2–1.9 eV and suitable energy level is a promissing material for photoelectrocatalytic reduction of CO2. However, the serious photocorrosion limits its performance improvement. Herein, an in-situ synthesis route is designed to fabricate 0D/1D CuFeO2/CuO nanowire heterojunction arrays with large specific surface. The nanowire heterojunction arrays presented excellent activity for photoelectrochemical reduction of CO2 to ethanol with an optimal faradaic efficiency of 66.73% at - 0.6 V (vs. Ag/AgCl). A heterojunction is formed between CuFeO2 and CuO, and the enhanced charge transfer mechanism is proposed based on the measurement of energy band structures. Under the action of interfacial built-in electric field of heterojunction, photogenerated holes are transferred from the valence band of CuO to CuFeO2, and photogenerated electrons are transferred from the conduction band of CuFeO2 to CuO with high selective reduction of CO2 to ethanol.

Electrocatalytic Overall Water Splitting Induced by Surface Reconstruction of an Iron-Modified Ni2P/Ni5P4 Heterojunction Array Encapsulated into a N-Doped Carbon Layer

Reasonable development of high-efficiency and robust electrocatalysts for efficient electrocatalytic water splitting at high current density is hopeful for renewable energy, but the real challenge is substituting the precious metal catalysts. Herein, ultrathin Fe-modified Ni2P/Ni5P4 nanosheet arrays hybridized with N-doped carbon grown on Ni foam (Fe-Ni2P/Ni5P4@N-C) were synthesized via a solvothermal-pyrolysis strategy. Theoretical calculations and in situ Raman characterizations confirm that the Fe sites can facilitate the surface reconstruction of highly active NiOOH species and significantly lower the energy barrier for the formation of the *OOH intermediate owing to the electron coupling effect between Fe and the Ni2P/Ni5P4 heterostructure. On account of the structural advantages and compositional synergy, the optimized Fe-Ni2P/Ni5P4@N-C exhibits superior hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) activities with an overpotential of 105 and 280 mV to reach 10 and 50 mA cm-2, respectively, and can work stably for 60 h at 100 mA cm-2. Impressively, the electrolyzer with Fe-Ni2P/Ni5P4@N-C only needs 1.56 V to achieve 10 mA cm-2 current density for water splitting. This protocol not only provides inspiration for designing transitional metal electrocatalysts for water splitting but also puts forward a pathway for practical application.