Interfacial Junctions Research Articles

Bipolar Membranes Via Divergent Synthesis: On the Interplay between Ion Exchange Capacity and Water Dissociation Catalysis.

Bipolar membranes (BPMs) enable the operation of electrochemical reactors with electrode compartments in different chemical environments or pH. The transport properties at the microscopic scale are dictated by the composition and morphology of the interfacial junctions as well as the specific chemistry of the ion-exchange layers that support the current of protons and hydroxide ions. This work elucidates the relation between water-dissociation efficiency and the physicochemical properties of the individual ion-exchange membrane layers in the poly(styrene-b-poly(ethylene-ran-butylene)-b-polystyrene) (SEBS)-based BPM. The optimal water dissociation performance of three previously reported water-dissociation catalysts in the SEBS-based BPM was examined, with junction thickness of graphene oxide > TiO2 > SnO2, resulting in disparate junction morphologies at the BPM's interface. A hybrid junction system, which included both the effective water dissociation catalyst SnO2 and direct contacting of the ion-exchange membrane layer, exhibited high water dissociation efficiency. This was likely due to the immediate ion transport pathway provided by direct membrane contact around the catalyst, which also improved the interfacial adhesion. A higher ion exchange capacity (IEC) in BPMs substantially enhanced the water dissociation performance in BPMs without water-dissociation catalysts. However, the incorporation of the effective SnO2 catalyst into the BPMs with a lower IEC significantly improved performance, an effect attributed to the hybrid junction system. Additionally, the increase in water uptake and ion conductivity of the cation exchange layer with higher IEC suggested that the cation exchange layer and its interface to the water-dissociation catalyst layer may play a key role in water dissociation. This study identifies the key parameters of individual BPM components and their interactions to water dissociation performance, offering new insights to guide in the construction of future BPMs optimized for enhanced water dissociation efficiency at high current densities.

Fuzzy logic with two-dimensional interfacial junction transistors

Fuzzy logic with two-dimensional interfacial junction transistors

Ab initio study of highly tunable charge transfer in β−RuCl3 /graphene heterostructures

Heterostructures of graphene in proximity to magnetic insulators open the possibility to investigate exotic states emerging from the interplay of magnetism, strain and charge transfer between the layers. Recent reports on the growth of self-integrated atomic wires of β−RuCl3 on graphite suggest these materials as versatile candidates to investigate these effects. Here we present detailed first-principles calculations on the charge transfer and electronic structure of β−RuCl3/graphene heterostructures and provide a comparison with the work function analysis of the related honeycomb family members α−RuX3 (X = Cl,Br,I). We find that proximity of the two layers leads to a hole-doped graphene and electron-doped RuX3 in all cases, which is sensitively dependent on the distance between the two layers. Furthermore, strain effects due to lattice mismatch control the magnetization which itself has a strong effect on the charge transfer. Charge accumulation in β−RuCl3 strongly drops away from the chain making such heterostructures suitable candidates for sharp interfacial junctions in graphene-based devices. Published by the American Physical Society 2024

Efficient photocatalytic degradation of ciprofloxacin using floating α-NiMoO4/mpg-C3N4/EP under visible light

Conventional water treatment processes often fail to effectively remove antibacterial drugs, necessitating advanced strategies. This study presents the synthesis of novel floating, visible light-active α-NiMoO4/mpg-C3N4/EP composites for the removal of ciprofloxacin (CFX), a widely used quinolone antibiotic, from water. These composites are easily recoverable, highly stable, and demonstrate excellent reusability. The optimal photocatalyst, NC-101/EP (α-NiMoO4/mpg-C3N4 = 10:1), achieved 96.2 ± 1.1% degradation of CFX at 1.6 g L−1 within 80 min under visible light, significantly outperforming previous benchmarks. This high efficiency is attributed to the formation of interfacial junctions and a built-in electric field, which enhanced charge transfer and hydroxyl radical generation through an S-scheme mechanism. Fluorescence spectroscopy provided precise monitoring of CFX degradation without interference from coexisting intermediates. Density functional theory (DFT) calculations revealed that hydroxyl radicals initiated highly favorable and spontaneous oxidation of CFX, with a reaction rate constant of 6.04 × 109 M−1 s−1. The preferred oxidation pathway followed the sequence: HO-addition > H-abstraction > single electron transfer. Four degradation pathways were identified, with key intermediates confirmed by high-resolution mass spectrometry. The process also significantly reduced CFX toxicity, ensuring minimal environmental impact. These findings position NC-101/EP as a promising photocatalyst for large-scale water treatment applications targeting antibiotic contamination.

Strong absorption of silica over full solar spectrum boosted by interfacial junctions and light–heat–storage of Mg(OH)2–(CrOx–SiO2)

Strong absorption of near-infrared (NIR) light is essential for efficient solar energy applications. NIR absorption primarily depends on the surface plasmon resonance of incident light with free charge carriers (FCCs). We demonstrated that S-scheme interfacial junctions (IJs) can substantially enhance FCC density, light-harvesting, photocurrent intensity, long lifetime of the charge carriers and photothermal effects, paving a way for novel light-material design. Abundant S–scheme IJs are constructed in CrOx–SiO2 nanoparticles, which increase the FCCs outstandingly and enhance light absorption exceptionally over the entire solar spectrum. IJs’ construction enables silica to harvest solar energy strongly. Doped with multifunctional CrOx–SiO2 nanoparticles, the photothermal-dehydration conversion and the stored heat of Mg(OH)2 can be improved by 7.0- and 5.1-times upon 30-min irradiation, respectively. The reversibility of the photothermal charge–discharge cycles of Mg(OH)2 improves 19.3 times. The thermal-storage kinetics is substantially improved owing to the reduction of the dehydration activation energy (−15.2 %). Mg(OH)2–CrOx–SiO2 composite is an excellent one-step system of light–heat–storage.

Multiphasic titania photoanode: A facile phase assisted approach to enhance the photoelectrochemical and photovoltaic performance

A facile low-temperature method has been proposed and utilized to synthesize pristine and multiphasic titania. Increasing reactant acid content led to the phase transition of titania from pristine anatase to triphasic anatase-rutile-brookite mixed phase; then to biphasic anatase-rutile mixed phase and ultimately pristine rutile. Morphological differences between the samples led to different dye loading on the Dye Sensitized Solar Cell (DSSC) photoanodes, with anatase showing highest loading. However, the Electrochemical Impedance Spectroscopic (EIS) analyses revealed that the triphasic titania photoanode showed superior charge transport ability as evidenced by the lowest charge transfer resistance and highest carrier lifetime. This led to the triphasic DSSC showing a photoconversion efficiency of 4.23 % which is 45 % greater than the reference DP25 DSSC and 72 % better than that of the anatase DSSC despite having a 24 % lower dye loading. These factors suggest that the charge transport properties precede the dye loading capability of the photoanode in determining the DSSC performance. The intimate ternary interfacial junction between the anatase, rutile and brookite phases may be responsible for the enhanced charge transport properties of the triphasic titania. Thus, it is essential to ensure superior photoanode charge transport characteristics to enhance the DSSC performance.

In situ fabrication of oxygen deficient Bi2MoO6/InVO4/CeVO4 dual S-scheme ternary heterostructure for robust photocatalytic H2 and H2O2 production

Mild in situ synthesis of ternary dual S-scheme heterostructure photocatalyst with high redox ability of photo-excitons is a pragmatic approach for achieving rapid activation of tenacious atmospheric molecules. In the present study, a series of Bi2MoO6/InVO4/CeVO4 ternary heterostructures were constructed by in situ deposition of Bi2MoO6 nanoplates over one pot synthesised InVO4/CeVO4 using a facile oil bath heating method. The as-synthesised heterostructure materials were comprehensively characterised to understand their structural, optical, electrochemical and morphological properties. The ternary heterostructure displayed a distinct morphology consisting of Bi2MoO6 nanoplates, CeVO4 nanosheets and InVO4 nanorods. The significant intergrowth among the constituent phases through the in situ coupling strategy also led to the construction of tight interfacial microscopic junctions. The important attributes of the ternary heterostructures included intense photon absorption in whole UV–visible region, drastic decrease in photogenerated charge recombination and higher excited state lifetime. Both InVO4 and CeVO4 individually as well as the ternary heterostructure contained surface oxygen vacancies that further promoted efficient charge separation and activation of atmospheric molecules. The optimised ternary photocatalyst displayed 2314 μmol/g/h H2 generation and 1700 μM/g/h H2O2 production which are 12–86 and 11–27 times higher than the pristine semiconductors, respectively. Detailed band position assessment and radical entrapment analysis suggested the occurrence of a dual S-scheme charge transfer mechanism that rationally accounted for the remarkable enhancement in the photocatalytic performance.

Harnessing the Trade‐Off between CoFe/Fe3C Interfacial Junction with Unparalleled Potential Gap of 0.58 V for Reversible Oxygen Electrocatalysis: Application toward Liquid and Solid‐State Zn‐Air Batteries

AbstractEffective integration of multiple active moieties and strategic engineering of coordinated interfacial junctions are crucial for optimizing the reaction kinetics and intrinsic activities of heterogeneous electrocatalysts. Herein, a simple integrated heterostructure of biphasic Co0.7Fe0.3/Fe3C embedded on in situ grown N‐doped carbon sheets is constructed. Rationally designed CoFe/Fe3C‐T2 owns more accessible active sites and interfacial junction effects, cooperatively boosting the electron and mass transfer, needed for multifunctional electrocatalysis. Leveraging the synergistic effect of dual active sites, CoFe/Fe3C‐T2 demonstrates outstanding oxygen electrocatalytic activity in alkaline medium with an ultra‐low potential gap of 0.58 V, surpassing the recently available state‐of‐the‐art catalysts. Moreover, CoFe/Fe3C‐T2 air‐electrode achieves a high peak power density of 249 mW cm−2, a large specific capacity of 808 mAh g−1 and excellent cycling stability for aqueous Zn‐air batteries. Remarkably, the solid‐state flexible ZAB also exhibits satisfactory performance, showcasing an open‐circuit voltage of 1.43 V and a peak power density of 66 mW cm−2. These outstanding results push this catalyst to the top of the list of non‐noble metal‐based electrode materials. This work offers a viable method for using the active‐site‐uniting strategy to create double‐active‐site catalysts, which may find real‐time applications in energy conversion/storage devices.

Reliable wafer-scale integration of two-dimensional materials and metal electrodes with van der Waals contacts

Since the first report on single-layer MoS2 based transistor, rapid progress has been achieved in two-dimensional (2D) material-based atomically thin electronics, providing an alternative approach to solve the bottleneck in silicon device miniaturization. In this scenario, reliable contact between the metal electrodes and the subnanometer-thick 2D materials becomes crucial in determining the device performance. Here, utilizing the quasi-van der Waals (vdW) epitaxy of metals on fluorophlogopite mica, we demonstrate an all-stacking method for the fabrication of 2D devices with high-quality vdW contacts by mechanically transferring pre-deposited metal electrodes. This technique is applicable for complex device integration with sizes up to the wafer scale and is also capable of tuning the electric characteristics of the interfacial junctions by transferring selective metals. Our results provide an efficient, scalable, and low-cost technique for 2D electronics, allowing high-density device integration as well as a handy tool for fundamental research in vdW materials.

Photocatalytic CO2 reduction of CuO-Zn1-xCuxO (ZCO)/Ti3C2Tx MXene heterojunctions with enhanced interfacial charge transfer

Photocatalytic CO2 reduction reaction (CO2RR) synthesis of recycled fuel is a promising pathway to assist the mitigating fossil fuel depletion. Finding efficient and inexpensive high performance CO2RR semiconductor photocatalysts is a giant challenge in the field of photocatalytic reduction. This work constructs the novel-designed interfacial Schottky junction of CuO-Zn1-xCuxO (ZCO)/Ti3C2Tx via electrostatic spinning and electrostatic self-assembly techniques. The catalysts exhibit tight contact heterogeneous interface companies with enhanced CO2 chemisorption capability and proved by various characterizations for efficient carrier separation and migration capacity. The optimized ZCO/Ti3C2Tx nanosheet composites significantly improved their photocatalytic performance. The best samples yielded 5.855 and 2.518 μmol g−1 h−1 of CO and CH4, which are 6 and 1.73 times higher than the conversion of ZCO, respectively, and maintain stability after four cycles without the use of sacrificial agents. In addition, the mechanism and reaction pathways of the photocatalytic process are proposed through In-situ diffuse reflectance Infrared Fourier Transform Spectroscopy (In-situ DRIFTS) and X-ray absorption near edge structure (XANES) analysis. This work provides a new semiconductor/co-catalyst system for the photocatalytic reduction of CO2 and demonstrates that Ti3C2Tx MXene is a hopeful and inexpensive co-catalyst.

The impact of membrane orientation on ion flux in bipolar membranes

Bipolar membranes (BPMs) are asymmetric, layered ion exchange membranes that are increasingly being explored for use in electrochemical devices. This study aims to investigate the effect that the direction of a diffusive driving force across a salt solution concentration gradient has on the flux through a BPM due to its asymmetric nature. BPMs were fabricated using PiperION poly(aryl piperidinium) A40 as the anion exchange layer (AEL) and Nafion 212 as the cation exchange layer (CEL) with no interfacial junction catalyst. The permeability of sodium chloride through the BPM membranes was measured across a 0.5molL-1 concentration differential for both orientations of the membrane, e.g. AEL facing the 0.5molL-1 NaCl solution versus the CEL facing the 0.5molL-1 NaCl solution. A flux differential of (76.3 ± 4.8)% was measured for the BPM depending on the direction of the driving force. A model based on Fick’s law and the Donnan equilibrium was developed and used to show that the flux differential results from changes in the ionic environment at the AEL–CEL junction due to differences in the ion diffusion coefficients and fixed charge concentrations of the two layers.

An organic/inorganic Z-scheme heterojunction Yb-MOF/BiOBr for efficient photocatalytic removal of NO

The advantages of visible light-driven catalysts with good light absorption, fast charge separation rate and high redox capacity are compelling. However, conventional inorganic semiconductor, such as pure BiOBr (BOB), showed a rapid photogenerated carriers recombination rate and low solar energy utilization ability, which limited the practical application of its photocatalytic performance. In this work, a novel organic/inorganic interleaved (Z-scheme) heterojunction Yb-MOF/BiOBr (Yb-MOF/BOB) photocatalyst was successfully synthesized. Compared with a single component, the Yb-MOF/BOB heterojunction exhibited significantly enhanced performance in photocatalytic oxidation of NO under visible light. Among them, Yb-MOF/BOB-20 had the best photocatalytic NO removal effect, up to 6424 ppb/g, which was 2.8 times and 4.2 times that of BOB and Yb-MOF, respectively. Photoelectrochemical characterization confirmed that the formation of heterojunctions broadened the absorption sidebands and increased the charge transfer at the interfacial junction of Yb-MOF/BOB. Combined with UPS, ESR and in-situ DRIFTS analysis, possible photocatalytic mechanisms were revealed, in which the formation of the Yb-MOF/BOB heterostructure endowed its high charge mobility and strong redox ability. Therefore, this work provided an effective way for photocatalytic removal of NO, and offered new ideas for developing heterogeneous photocatalysts.

Self-Propelled nanojets an interfacial Schottky junctions modulated oxygen vacancies enriched for enhanced photo-Fenton degradation of organic contaminant: Improving H2O2 generation, Fe3+/Fe2+ cycle and enhancing plant metabolism (Chemosphere, Volume 314, February 2023, 137516)

Self-Propelled nanojets an interfacial Schottky junctions modulated oxygen vacancies enriched for enhanced photo-Fenton degradation of organic contaminant: Improving H2O2 generation, Fe3+/Fe2+ cycle and enhancing plant metabolism (Chemosphere, Volume 314, February 2023, 137516)

Cobalt enhanced (H/C-CdS)/CeO2 activity for visible light catalytic oxidation of formaldehyde at room temperature

The visible light catalytic oxidation of formaldehyde (HCHO) at room temperature is of great interest for improving the indoor air quality. Here, a cobalt (Co)-doped CdS-based catalyst ((H/C-CdS)/CeO2) with high visible light catalytic activity was successfully synthesized for HCHO removal at room temperature. Co addition enhanced the catalytic activity of (H/C-CdS)/CeO2, and the HCHO conversion rate reached 99.5 % for a 1 mg/L aqueous HCHO solution on the Co–(H/C-CdS)/CeO2 catalyst after 1 h at room temperature under visible light, which was greater than that of (H/C-CdS)/CeO2 (92.0 %). The (H/C-CdS)/CeO2 and Co–(H/C-CdS)/CeO2 catalysts were systemically characterized, and the results showed that the interfacial phase junction between the hexagonal (H) and cubic (C) phases of the CdS nanoparticles (NPs) and the synergistic effect of the type II heterojunction between the CdS NPs and CeO2 nanosheets (NSs) promoted the separation of e-/h+. Moreover, the addition of Co species strongly promoted the separation of photogenerated carriers. The excellent photocatalytic activity was attributed to the good dispersion of CdS NPs, which broadened the light absorption range, exposed more active sites, and provided close contact, decreasing the migration distance of photogenerated electron-hole pairs. After that, the visible light catalytic oxidation mechanism of HCHO on both (H/C-CdS)/CeO2 and Co–(H/C-CdS)/CeO2 followed the reaction pathway of HCHO to (CO2 + H2O).

Proton doping enhanced flexoelectricity and photocurrent in hydrogen-charged TiO2

The intrinsic flexoelectric effect observed in oxide materials often falls below the desired threshold for practical applications. In this work, we demonstrate proton doping in insulating rutile TiO2 crystal as an effective approach to significantly increase flexoelectricity by more than two orders of magnitude. We attribute the noteworthy enhancement of flexoelectricity to the dual impact of proton doping in oxide materials. First, proton doping serves to induce the presence of charge carriers, resulting in the generation of flexoelectric currents. Second, proton doping induces expansion and distortion of the lattice structure, leading to an amplified flexoelectric field when the crystal experiences a strain gradient. The formation of O–H bonding in TiO2 crystal provides another route to break centrosymmetry according to lattice distortion of the TiO2 lattice, resulting in a larger flexoelectric field. In addition, the introduction of proton doping in TiO2 single crystals leads to a substantial increase in photocurrent by effectively flattening the interfacial Schottky junction. This phenomenon results in a three-order of magnitude enhancement of the photocurrent. Our work broadens the horizon of study on dielectric materials through proton doping and may also provide an approach that enables the utilization of dielectric materials in energy conversion applications.

Design of interfacial dual Schottky junctions to modulate charge transfer for enhanced piezo-assisted photocatalytic degradation RhB performances

Construction of piezo-assisted interfacial dual Schottky junction to regulate charge transfer and surface reaction rate for the photocatalytic degradation of RhB.

Fabrication of Cu2-xO thin films directly bondable to copper on aluminum nitride substrates using the sol-gel method

Controlling the oxygen content becomes a formidable challenge when using the traditional method of copper pre-oxidation to attach copper metal to AlN ceramic substrates. The issue results in copious amounts of copper oxide (CuO) formation. Excessive CuO causes voids to form at the interfacial junction, harming the long-term reliability of the copper-bonded substrate. To address these issues, this study employed the sol-gel technique, in which a copper-containing solution was applied to the AlN substrate via spin coating, followed by thermal treatment in a nitrogen-rich atmosphere. The goal was to create thin films of Cu2-xO to improve the adhesion between copper and AlN substrates. It was observed that the surface roughness of the resulting Cu2-xO thin film after 5 spin-coating cycles was the lowest (3.48 nm). Furthermore, at a fixed thickness of the Cu2-xO oxide layer (approximately 36 nm), insufficient oxygen content in the thin film heated at 250 °C prevented the formation of sufficient Cu–O eutectic liquid at high temperatures, resulting in insufficient copper-bonded substrate bonding strength (0.47 MPa). When the thin film was heated to 400 °C, the proportion of the CuO phase in the film increased, effectively increasing the bonding strength of the copper-bonded substrate (0.84 MPa).

Fabrication of TiO2 nanorods/γ-graphyne boosting junction-driven charge transfer for efficient photoelectrochemical water splitting

Photoelectrochemical (PEC) water splitting is a viable method for converting renewable solar energy into storable chemical energy. Herein, the newly emerged two-dimensional sp- and sp2-carbon hybridized graphyne sheets were successfully coupled with thin film-like arrays of titanium dioxide nanorods, forming an efficient 2D-1D heterojunction. The microstructure and composition of obtained γ-graphyne/TiO2 films were well characterized. And enhanced photoelectrochemical properties were demonstrated. The γ-graphyne/TiO2 photoelectrode achieves a photocurrent density of 1.31 mA/cm2 at 1.23 V (vs. RHE), which is 1.7 times over that of pristine titanium dioxide. An improvement of photoconversion efficiency by 2.2 folds was observed. The high PEC activity of γ-graphyne/TiO2 originates from band alignment and interfacial junction between π-conjugated graphyne sheets and TiO2 nanostructure, greatly promoting charge transfer and diminishing defective excitation and recombination. By virtue of the γ-graphyne nanosheets, largely increased number of useful photons and catalytic active sites are triggered. This work provides a reference for the photoelectrochemical application of semiconductive γ-graphyne and a specific and proven method for the utilization of solar energy.

Key Strategies for Enhancing H2 Production in Transition Metal Oxide Based Photocatalysts

AbstractTransition metal oxides (TMOs) were one of the first photocatalysts used to produce hydrogen from water using solar energy. Despite the emergence of many other genres of photocatalysts over the years, TMO photocatalysts remain dominant due to their easy synthesis and unique physicochemical properties. Various strategies have been developed to enhance the photocatalytic activity of TMOs, but the solar‐to‐hydrogen (STH) conversion efficiency of TMO photocatalysts is still very low (<2 %), which is far below the targeted STH of 10 % for commercial viability. This article provides a comprehensive analysis of several widely used strategies, including oxygen defects control, doping, establishing interfacial junctions, and phase‐facet‐morphology engineering, that have been adopted to improve TMO photocatalysts. By critically evaluating these strategies and providing a roadmap for future research directions, this article serves as a valuable resource for researchers, students, and professionals seeking to develop efficient energy materials for green energy solutions.

Key Strategies for Enhancing H2 Production in Transition Metal Oxide Based Photocatalysts.

Transition metal oxides (TMOs) were one of the first photocatalysts used to produce hydrogen from water using solar energy. Despite the emergence of many other genres of photocatalysts over the years, TMO photocatalysts remain dominant due to their easy synthesis and unique physicochemical properties. Various strategies have been developed to enhance the photocatalytic activity of TMOs, but the solar-to-hydrogen (STH) conversion efficiency of TMO photocatalysts is still very low (<2 %), which is far below the targeted STH of 10 % for commercial viability. This article provides a comprehensive analysis of several widely used strategies, including oxygen defects control, doping, establishing interfacial junctions, and phase-facet-morphology engineering, that have been adopted to improve TMO photocatalysts. By critically evaluating these strategies and providing a roadmap for future research directions, this article serves as a valuable resource for researchers, students, and professionals seeking to develop efficient energy materials for green energy solutions.