Heterojunction Electrode Research Articles

Bilayer Boost to UV Assisted Supercapacitors: Enhanced Performance with Transparent TiO2/MoO3 Heterojunction Electrode

Photo‐assisted supercapacitor is a promising smart device component for achieving both energy conversion and storage. The photo‐assisted functionality in a supercapacitor is realized through the choice of photo responsive electrode material under suitable illumination conditions. The well‐known electrochemically active electrode materials are wide band gap semiconductors which absorb strongly in UV light. However, most of the prior studies on photo‐assisted supercapacitors used visible light. Herein, we present a transparent TiO2/MoO3 bi‐layer heterojunction made by simple solution process as an efficient electrode for photo‐assisted supercapacitors under UV light illumination. The electrochemical performance of the electrode is significantly enhanced even with a less intense (0.05mW/cm2) UV light, compared to dark as well as the single layer electrode under same illumination condition. The highest areal capacitance of 63.25 mF/cm2 at 0.1 mA/cm2 is achieved, that surpasses most of the recent relevant reports. The synergetic effect of UV illumination and the built‐in potential at the type II heterojunction interface encourages ion insertion and better collection of the photo‐generated carriers. The unique bi‐layer design also leads to better rate capability features. Thus, the work presents a new prospect for the development of transparent energy storage devices to be used in future smart technologies.

Electrocatalytic reduction of nitrate by Cu valence-regulated heterojunction electrode: A key role of Cu(I/II) composites and high nitrate reduction efficiency

Electrocatalytic reduction of nitrate by Cu valence-regulated heterojunction electrode: A key role of Cu(I/II) composites and high nitrate reduction efficiency

Poole-Frenkel conduction in CdS single-layered and CdS/SnS2 heterojunction electrode system

In this communication, the prevalence of Poole-Frenkel conduction mechanism in two distinct semiconductor systems, CdS single-layered and CdS/SnS2 heterojunction electrode systems, is reported. X-ray diffraction (XRD) exhibits the formation of CdS quantum dots (QDs). A High resolution transmission electron microscopy (HRTEM) shows a discrete particle distribution of SnS2, tends to assemble into nanosheets. Poole-Frenkel conduction arises due to the trap distribution of CdS dots, modified by SnS2 sheets. Furthermore, the formation of heterojunctions with SnS2 shows promising enhancement in charge transport, characterized by reduced trap density and improved conductivity compared pristine CdS. The findings provide valuable insights into the fundamental charge transport processes in CdS/SnS2 system and offer potential avenues for optimizing the performance of electronic devices.

High-capacity and high-stability capacitive desalination with dual redox-active MnCo2S4/g-C3N4 heterojunction electrode

Capacitive deionization (CDI) utilizing dual redox-active electrodes has shown significant promise in desalinating low-concentration brackish waters, which is crucial for addressing global freshwater shortages. However, improvements in salt adsorption capacity and long-term operational stability are still required. In this study, we introduce, for the first time, a binary metal sulfide MnCo2S4/g-C3N4 (MCS-CN) heterojunction as a CDI electrode. The innovative integration of dual redox-active centers and heterojunction structures in the MCS-CN composite electrodes underscores their potential for achieving both high capacity and stability in capacitive desalination applications. The microscopic morphology, crystal structure, pore structure, and surface valence properties of the MCS-CN heterojunction composite materials were extensively characterized using various analytical techniques. In-situ X-ray diffraction, refined ex-situ X-ray photoelectron spectroscopy, three-electrode electrochemical analysis, and theoretical calculations were employed to elucidate the electrosorption and desorption mechanisms of sodium ions with the MCS-CN electrodes and to clarify the enhanced desalination performance of the binary metal sulfide-based heterojunction structure. As a result, the optimal MCS-CN-40 electrode exhibited the highest salt removal capacity of 71.64 mg g−1 and maintained stable desalination performance over 100 cycles in a 500 mg L−1 NaCl solution. This innovative approach provides a noval perspective for developing heterojunction electrodes with high redox activity and efficient desalination performance.

Construction of electron-interactive CoMoO4 @ CoP core–shell structure on boron-doped graphene aerogel as strongly interface coupled hybrid electrodes for high flexible supercapacitor

Exploring high energy density, lightweight and self-supporting flexible electrodes is essentially significant to flexible energy storage equipment. Herein, boron-doped three-dimensional porous graphene aerogel (BGA) is engineered and novel flake-like CoP encapsulating flower-like CoMoO4 core–shell structure is arranged on it (CoMoO4@CoP/BGA) utilizing a combination of solvothermal, freeze-drying and vapor deposition techniques. Boron-doped graphene aerogel as flexible self-supporting positrode creates a unique three-dimensional porous interface with a larger specific surface area, which is conducive to exposing more active sites and avoids the additional process of adding binders and conductive agents. The heterointerface engineering of CoP epitaxial growth on CoMoO4 can efficiently enhance electrolyte ions adsorption ability and fast reaction kinetics. As expected, the fabricated CoMoO4@CoP/BGA demonstrates a better specific capacitance of 3056.4F/g than that of CoMoO4/BGA (1582.4F/g) and pure CoMoO4 (669.2F/g), apart from retains the remarkable cyclic stability of 88.4 % after 10,000 cycles. Furthermore, a hybrid supercapacitor composed of CoMoO4@CoP/BGA and BGA can provide a high energy density of 50.2 Wh kg−1 at 800.0 W kg−1, and retains good capacitance retention of 95.6 % after 10,000 cycles, which can be attributed to the large specific surface of B doping 3D porous graphene aerogel and the rich strong coupling interface synergy between CoP and CoMoO4. More importantly, this work provides important guidance for the design of heterojunction electrodes based on heteroatom doped graphene aerogel and phosphides @ oxide based flexible energy storage devices.

Photoelectrocatalysis degradation of P-aminophenol using PbO2-TiO2 heterojunction electrode: Catalytic, theoretical calculating and mechanism

To lengthen the lifetime and extend the potential commercial applications of lead dioxide electrode. Herein, PbO2–TiO2 heterostructured electrodes were fabricated via direct current electrodeposition and the surface of the electrode was characterized by electron microscopy (EDS), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The PbO2–TiO2 heterostructure electrode could produce an obvious photocurrent under UV irradiation, indicating a photoelectrocatalytic reaction. The PbO2–TiO2 heterostructured electrode was examined using density functional theory calculations(DFT). Work function(WF) confirmed that the applied electric field is conducive to the movement of photoelectrons, which promotes the photoelectrocatalysis effect. The nudged elastic band(NEB) results showed that the PbO2–TiO2 heterostructure electrode can promote the formation of •OH by reducing the activation barrier. The PbO2–TiO2 electrode was used as an anode to treat P-aminophenol (PAP) wastewater simulated wastewater and real PAP wastewater via photoelectrocatalytic degradation. The PbO2–TiO2 electrode effectively removes chemical oxygen demand (COD) from actual wastewater was 54.93 %,The after-treated Pb2+ concentration (0.037 mg·L−1) was lower than China’s wastewater discharge standard (1 mg·L−1). Finally, the degradation pathway of PAP was determined based on the intermediates detected using gas chromatography–mass spectrometry and the reactive sites of PAP were predicted using the Fukui function.These results suggest that the photoelectrocatalysis degradation of PAP using electrodes is feasible.

Porous two-dimensional CuSe@BiOI isotype heterojunction with highly exposed (1 0 2) facets for efficient photoelectrocatalytic CO2 reduction and photodetection

Using photoelectrochemical technology to construct efficient photoelectric materials has aroused extensive research interest. In this study, we propose a two-dimensional porous CuSe@BiOI isotype heterojunction photocathode for CO2 reduction to formic acid. The heterojunction was constructed by the epitaxial growth of high-quality oriented BiOI nanosheets onto the porous CuSe framework. The CuSe framework as a template to ensure the formation of the (102) facets of BiOI and the isotropic charge transport characteristics of the (102) surface greatly improve the efficiency of charge separation and transfer. This CuSe@BiOI isotype heterojunction electrode can efficiently reduce CO2 to formic acid with a selectivity of up to 80.5 % in 0.5 M potassium bicarbonate aqueous solution. Meanwhile,the performance of the photodetector based on CuSe@BiOI heterostructure is 6.97 × 1011 Jones and a response rate of 87.13 mA W−1. This finding provides a new approach to designing stable heterojunction photoelectrocatalysts with isotropy.

Enhanced Uranium Extraction via Charge Dynamics and Interfacial Polarization in MoS2/GO Heterojunction Electrodes.

The removal of uranyl ions (UO2 2+) from water is challenging due to their chemical stability, low concentrations, complex water matrix, and technical limitations in extraction and separation. Herein, a novel molybdenum disulfide/graphene oxide heterojunction (MoS2/GO-H) is developed, serving as an effective electrode for capacitive deionization (CDI). By combining the inherent advantages of electroadsorption and electrocatalysis, an innovative electroadsorption-electrocatalysis system (EES) strategy is introduced. This system utilizes interface polarization at the MoS2 and GO interface, creating an additional electric field that significantly influences carrier behavior. The MoS2/GO-H electrode, with its extraordinary adsorption capacity of 805.57mgg-1 under optimal conditions, effectively treated uranium-laden wastewater from a mine, achieving over 90% removal efficiency despite the presence of numerous competing ions at concentrations significantly higher than UO2 2+. Employing density functional theory (DFT) and ab initio molecular dynamics (AIMD) simulations, it is found that the MoS2/GO-H total charge density at the Fermi level, enhanced by interfacial polarization, surpasses that of separate MoS2 and GO, markedly boosting conductivity and electrocatalytic effectiveness.

Co-sensitization of Copper Indium Gallium Disulfide and Indium Sulfide on Zinc Oxide Nanostructures: Effect of Morphology in Electrochemical Carbon Dioxide Reduction.

Recent advances in nanoparticle materials can facilitate the electro-reduction of carbon dioxide (CO2) to form valuable products with high selectivity. Copper (Cu)-based electrodes are promising candidates to drive efficient and selective CO2 reduction. However, the application of Cu-based chalcopyrite semiconductors in the electrocatalytic reduction of CO2 is still limited. This study demonstrated that novel zinc oxide (ZnO)/copper indium gallium sulfide (CIGS)/indium sulfide (InS) heterojunction electrodes could be used in effective CO2 reduction for formic acid production. It has been determined that Faradaic efficiencies for formic acid production using ZnO nanowire (NW) and nanoflower (NF) structures vary due to structural and morphological differences. A ZnO NW/CIGS/InS heterojunction electrode resulted in the highest efficiency of 77.2% and 0.35 mA cm-2 of current density at a -0.24 V (vs. reversible hydrogen electrode) bias potential. Adding a ZTO intermediate layer by the spray pyrolysis method decreased the yield of formic acid and increased the yield of H2. Our work offers a new heterojunction electrode for efficient formic acid production via cost-effective and scalable CO2 reduction.

Suppressing Ion Migration by Synergistic Engineering of Anion and Cation toward High-Performance Inverted Perovskite Solar Cells and Modules.

Ion migration-induced intrinsic instability and large-area fabrication pose a tough challenge for the commercial deployment of perovskite photovoltaics. Herein, an interface heterojunction and metal electrode stabilization strategy is developed by suppressing ion migration via managing lead-based imperfections. After screening a series of cations and nonhalide anions, the ideal organic salt molecule dimethylammonium trifluoroacetate (DMATFA) consisting of dimethylammonium (DMA+) cation and trifluoroacetate (TFA-) anion is selected to manipulate the surface of perovskite films. DMA+ enables the conversion of active excess and/or unreacted PbI2 into stable new phase DMAPbI3, inhibiting photodecomposition of PbI2 and ion migration. Meanwhile, TFA- can suppress iodide ion migration through passivating undercoordinated Pb2+ and/or iodide vacancies. DMA+ and TFA- synergistically stabilize the heterojunction interface and silver electrode. The DMATFA-treated inverted perovskite solar cells and modules achieve a maximum efficiency of 25.03% (certified 24.65%, 0.1 cm2) and 20.58% (63.74 cm2), respectively, which is the record efficiency ever reported for the devices based on vacuum flash evaporation technology. The DMATFA modification results in outstanding operational stability, as evidenced by maintaining 91% of its original efficiency after 1520 h of maximum power point continuous tracking.

An “On‐Site Transformation” Strategy for Electrochemical Formation of TiO2 Nanoparticles/Ti3C2Tx MXene/Reduced Graphene Oxide Heterojunction Electrode Controllably toward Ultrasensitive Detection of Uric Acid

Ascribing to the abundance of Ti element, exceptional electrical conductivity, and electrocatalytic performance, titanium carbide MXene (Ti3C2Tx, MX) is considered as an ideal conductive matrix and employed for in situ preparation of promising TiO2 NPs@MX/reduced graphene oxide (rGO) heterojunction electrodes for uric acid (UA) detection. However, the incapability of achieving the controllable growth and synthesis of TiO2 nanoparticles (NPs) on MX nanosheets is a bottleneck in fabricating optimal and controllable TiO2 NPs@MX hybrid. Herein, an “on‐site transformation strategy” is developed to synthetize TiO2 NPs@MX/rGO heterojunction platform controllably by in situ electrochemical oxidizing MX nanosheets at various treatment times. The proposed approach allows for the greater operability to controllably grow and synthetize TiO2 NPs on the surface of MX nanosheets. The heterojunction electrodes present a linear voltammetric response toward UA in the concentration range of 0.003–0.3 and 0.3–300 μm and a low detection limit of 0.78 nm (S/N = 3). Additionally, a handheld electrochemical system with a smartphone readout is developed for point‐of‐care health monitoring, enabling fast, precise, and specific recognition of UA in real urine samples. The study provides a facile and controllable approach to fabricate TiO2 NPs@MX/rGO heterojunction platform for future use in other biomolecules' detection.

Electrochemical Reduction of Flue Gas Denitrification Wastewater to Ammonia Using a Dual-Defective Cu2O@Cu Heterojunction Electrode.

Wet flue gas denitrification offers a new route to convert industrial nitrogen oxides (NOx) into highly concentrated nitrate wastewater, from which the nitrogen resource can be recovered to ammonia (NH3) via electrochemical nitrate reduction reactions (NITRRs). Low-cost, scalable, and efficient cathodic materials need to be developed to enhance the NH3 production rate. Here, in situ electrodeposition was adopted to fabricate a foamy Cu-based heterojunction electrode containing both Cu-defects and oxygen vacancy loaded Cu2O (OVs-Cu2O), which achieved an NH3 yield rate of 3.59 mmol h-1 cm-2, NH3 Faradaic efficiency of 99.5%, and NH3 selectivity of 100%. Characterizations and theoretical calculations unveiled that the Cu-defects and OVs-Cu2O heterojunction boosted the H* yield, suppressed the hydrogen evolution reaction (HER), and served as dual reaction sites to coherently match the tandem reactions kinetics of NO3-to-NO2 and NO2-to-NH3. An integrated system was further built to combine wet flue gas denitrification and desulfurization, simultaneously converting NO and SO2 to produce the (NH4)2SO4 fertilizer. This study offers new insights into the application of low-cost Cu-based cathode for electrochemically driven wet denitrification wastewater valorization.

Boosting hydrogen evolution kinetics of self-supported MoC-Mo2C heterojunction electrode by platinum decoration

Molybdenum carbide-based hydrogen evolution reaction (HER) electrocatalysts have attracted widespread attention with their low cost and relatively high catalytic activity. Despite the significant progress made in tuning the morphology and structure, the intrinsic catalytic activity of molybdenum carbide awaits further improvement. Herein, a Pt-decorated self-supported MoC-Mo2C electrode with super-intrinsic HER catalytic activity is prepared by a simple adsorption-electroreduction method. The HER performance is improved with increasing the loading of Pt. The optimal MoC-Mo2C-Pt heterojunction electrode has a low overpotential of 10 mA cm−2 (58 mV in H2SO4, 82 mV in KOH) and small Tafel slope (24 mV dec−1 in H2SO4, 29 mV dec−1 in KOH), which is reduced to 0.45–0.5, 0.7–0.8, and 0.4–0.7 times of pristine MoC-Mo2C, Pt foil, and commercial Pt/C (2 mg cm−2), respectively. The improved HER catalysis is attributed to the rapid dissociation of water on MoC-Mo2C and efficient desorption of hydrogen on Pt. Therefore, decorating carbides with Pt is an effective way to design HER catalysts with enhanced catalytic activities in a wide pH range.

Fabrication of a novel Z-S-scheme photocatalytic fuel cell with the Z-scheme TiO2/GO/g-C3N4 photoanode and S-scheme BiOAc1−xBrx/BiOBr photocathode for TC degradation

The upsurge of interest in the emergence of photocatalytic fuel cell systems (PFC) presents an efficient and environmentally friendly approach to wastewater treatment. In this work, a Z-scheme coupled with an S-scheme heterojunction electrode was used in the PFC, utilizing TiO2/GO/g-C3N4 as the photoanode and BiOAc1–xBrx/BiOBr as the photocathode. We systematically align the band structures between the anode and cathode, which facilitates the electron transfer between the electrodes. Our attempt successfully demonstrates that collaborative power generation facilitates the high efficiency of tetracycline hydrochloride (TC) degradation at both electrodes. The photoanode achieved a 94.87 % degradation rate for TC, while the photocathode exhibited a 96.33 % degradation rate after 2 h, surpassing pristine BiOBr and BiOAc by factors of ∼5.3 and ∼3.8, respectively. Furthermore, this work proposed a mechanism for electron generation, transport, and pollutant degradation mechanism in the PFC. Intermediate substances generated during the degradation of TC were analyzed through high-performance liquid chromatography-mass spectrometry (HPLC-MS) and ultraviolet photoelectron spectroscopy (UPS), while the optimal degradation pathway was confirmed using density functional theory (DFT). The findings of this work establish the feasibility of efficiently degrading pollutants through PFC treatment, introducing a novel system where various heterojunctions in bipolar materials collaborate with photocatalysis to effectively generate electricity and enhance pollutant removal.

The construction of a photocatalytic fuel cell based on piezoelectric-enhanced dual heterojunctions of PVDF–HFP supported 2D/3D composites toward photocatalytic degradation of tetracycline

Degradation sketch of a membrane fuel cell system constructed from I- and S-scheme heterojunction electrodes.

Unlocking the Design Paradigm of In-Plane Heterojunction with Built-in Bifunctional Anion Vacancy for Unexpectedly Fast Sodium Storage.

Transition metal chalcogenide (TMD) electrodes in sodium-ion batteries exhibit intrinsic shortcomings such as sluggish reaction kinetics, unstable conversion thermodynamics, and substantial volumetric strain effects, which lead to electrochemical failure. This report unlocks a design paradigm of VSe2- x /C in-plane heterojunction with built-in anion vacancy, achieved through an in situ functionalization and self-limited growth approach. Theoretical and experimental investigations reveal the bifunctional role of the Se vacancy in enhancing the ion diffusion kinetics and the structural thermodynamics of Nax VSe2 active phases. Moreover, this in-plane heterostructure facilitates complete face contact between the two components and tight interfacial conductive contact between the conversion phases, resulting in enhanced reaction reversibility. The VSe2- x /C heterojunction electrode exhibits remarkable sodium-ion storage performance, retaining specific capacities of 448.7 and 424.9 mAh g-1 after 1000 cycles at current densities of 5 and 10 A g-1 , respectively. Moreover, it exhibits a high specific capacity of 353.1 mAh g-1 even under the demanding condition of 100 A g-1 , surpassing most previous achievements. The proposed strategy can be extended to other V5 S8- x and V2 O5- x -based heterojunctions, marking a conceptual breakthrough in advanced electrode design for constructing high-performance sodium-ion batteries.

Wettability and heterojunction synergistic interface optimization guided Co doped MoS2/Ni3S2-GO/NF catalytic electrode to boost overall water splitting

Rationally designing cost-efficient, high-activity and durable electrocatalysts are used for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is sense to solve the energy crisis and conversion. Herein, the heterostructure superwetting Co–MoS2/Ni3S2-GO/NF electrode is successfully fabricated by a typical hydrothermal reaction and it's electrocatalytic performance is also systematically studied. Thanks to the establishment of Co doped MoS2/Ni3S2 heterojunction, the improvement conductivity by the addition of graphene oxide (GO), and the superhydrophilicity and superaerophobicity of microstructure, the electrode shows excellent catalytic characteristics and only need an overpotential of 123 mV for OER and 161 mV for HER to reach 10 mA cm−2 and can work steadily for 15 h in alkaline solution. Remarkebly, the superwetting heterojunction electrode demonstrated excellent overall water decomposition ability when used as bifunctional electrocatalyst in 1.0 M KOH and only 1.47 V is required to achieve 10 mA cm−2. Density functional theory (DFT) calculations show the constructed heterogeneous interface and Co doping are conducive to optimizing the chemisorption energy of hydrogen-containing intermediates. This work provides a new way of thinking that collaborative optimization of electrode structure and surface wettability regulation to increase the active area of reaction and accelerate the bubble release toward high-performance OER and HER electrodes.

Construction of electrochemical biosensors based on MoSe2@1T-MoS2 heterojunction for the sensitive and rapid detection of miRNA-155 biomarker in breast cancer

MiRNA-155 is a typical biomarker for breast cancer. Since its low concentration in the physiological environment and the limitations of conventional miRNA detection methods like Northern imprinting and RT-qPCR, convenient, real-time, and rapid detection methods are urgently needed. In this work, an electrochemical biosensor was constructed based on the flower-like MoSe2@1T-MoS2 heterojunction electrode material and specific RNA recognition probes, which can realize the rapid determination of miRNA-155 content with a wide detection range from 1 fM to 1 nM and a limit of detection (LOD) as low as 0.34 fM. Furthermore, the contents of miRNA-155 in blood samples of tumor-bearing mice and normal mice were measured as 724.93 pM and 21.42 pM, respectively by this biosensor, demonstrating its strong identification ability and miRNA-155 can be regarded as an ideal diagnostic marker. On this basis, a portable sensor platform was designed for on-site detection simulation and showed good recovery efficiency from 95.80% to 98.69%. Meanwhile, compared with the standard detection method RT-qPCR, the accuracy and reliability of the biosensor were verified, indicating that the biosensor has the potential to provide point-of-care testing (POCT) for the early diagnosis of breast cancer.

Flower-like CoP coated NiMoO4 nanorods as self-supported core-shell heterojunction electrode can facilitate oxygen evolution reaction at a low overpotential

Transition metal phosphates, as the most promising catalyst for oxygen evolution reaction (OER), have attracted much attention in recent years. In this work, CoP nanosheets are electrodeposited on NiMoO4 nanorods to form a self-supported core-shell structure electrode with CoP-NiMoO4 heterojunctions. Density functional theory (DFT) calculations demonstrate CoP-12@NiMoO4/NF electrode can reduce reaction energy barrier of rate-determining step (RDS) from 8.743 eV to 2.519 eV. In 1 M KOH, the electrode shows a low overpotential of 165 mV (10 mA cm−2), a low Tafel slope of 45 mV dec−1 and the significant stability. Compared with other non-noble metal OER electrocatalysts, the prepared CoP-12@NiMoO4/NF electrode exhibits better electrocatalytic activity, which can provide a new choice of electrocatalysts for future practical applications.

Facile in-situ deposition of three-dimensional Pt nanoballs of nickel nanorods heterojunction electrodes for hydrogen evolution reaction

Hydrogen is a kind of renewable energy for a friendly environment and can promote carbon emission reduction. The Platinum catalytic electrode is widely applied in hydrogen evolution reaction (HER) of water due to its low overpotential. However, it has affected its commercial application because of its high cost. Therefore, developing heterojunction catalysts with Platinum for HER is an effective way to achieve large-scale hydrogen production. In this work, we present a novel PtNBs/NiNRs heterojunction catalyst via the Pt nanoballs in-situ deposition on Ni nanorods array. The results demonstrate that the PtNBs/NiNRs electrodes have superior catalytic activity for HER in an alkaline condition. The hydrogen overpotential of PtNBs/NiNRs is −61.6 mV (RHE) in the alkaline solution, which is lower than the Pt electrode of −184mV. The Tafel plots and EIS were employed to investigate the mechanism and kinetics of the PtNBs/NiNRs in the alkaline solution. The nanostructures of Ni nanorobs and the Pt nanoballs active sites decrease the charge transfer resistance and increase the charge capacitance for the HER process compared to the Pt electrode. The PtNBs/NiNRs heterojunction catalyst electrodes demonstrate promising applications in HER because of their facile preparation, high efficiency, and low value.