Increase In Electron Mobility Research Articles

Enhancing efficiency of photoelectrochemical water splitting using zinc vanadate nanosheets (ZV) on manganese vanadate needle flowers (MV) supported by carbon nanofibers

Zinc and Manganese vanadates are highly regarded as potential photoanode materials for photoelectrochemical (PEC) water splitting due to their limited bandgap, varying optical and electrical characteristics based on their composition, and robust nature. To advance the practical use these materials, it is essential to creating precisely composed and structured Zinc and Manganese vanadates to enhance their overall effectiveness. In this work, we employed various morphologies, such as nanobelt flower like Zinc vanadate (ZV), nano-needle like Manganese vanadate (MV), a composite with ZV and MV, and a ZV-MV@CNF ternary composition. These novel morphologies grown on ITO substrate using a simple, hydrothermal approach without using any seed layer. The structural, surface, and optical examinations confirmed that the ZV-MV@CNF catalyst had superior visible light absorption, accelerated charge transfer, heterojunction interface between ZV and MV, and increased electron mobility, leading to outstanding photoelectrochemical performance. The photocurrent density of the ZV-MV@CNF photoanode reached 6.59 mA cm−2 at 1 V versus Ag/AgCl in a 0.25 M KOH solution under the illumination light. These results are ∼3.00, 3.52, and 1.28 times greater than the pristine ZV, MV, and ZV-MV, respectively. The fine-tuned ZV, MV, ZV-MV, and ZV-MV@CNF electrodes showed applied bias photon to current efficiency (ABPE) values of 0.09 %, 0.06 %, 0.14 %, and 0.18 %, respectively. The improved photoelectrochemical behavior of the ZV-MV@CNF electrode is credited to the excellent light absorption, and the remarkable catalytic and charge transport capabilities of CNFs. Therefore, these experimental results and characterization analysis suggested that advanced hierarchical nanostructures hold significant promise for water splitting applications.

Two-dimensional electron gases in AlYN/GaN heterostructures grown by metal–organic chemical vapor deposition

Wurtzite AlN alloyed with group 3 elements Sc and Y boosts the performance of GaN-based high-electron-mobility transistors (HEMTs) significantly as they increase the spontaneous polarization of the barrier layer and, thus, enhance the charge carrier density ns in the two-dimensional electron gas (2DEG) formed at the interface with the GaN channel. The emerging nitride Al1−xYxN additionally features an a lattice parameter matching to that of GaN at x = 0.07–0.11, allowing for the growth of strain-free barriers. Here, we demonstrate the growth of Al1−xYxN/GaN heterostructures for HEMTs by metal–organic chemical vapor deposition for the first time. The effect of the Y concentrations on the 2DEG is investigated in a Y concentration range from 3% to 15%. At 8% Y, a record mobility of 3200 cm2/(Vs) was measured at a low temperature (7 K). Room and low-temperature ns was at 1–2 × 1013 cm−2. Al0.92Y0.08N barriers were coherently strained to the GaN channel for barrier thicknesses from 5 to 15 nm. Finally, the deposition of Al1−xYxN/GaN heterostructures deposited on 4″ 4H–SiC wafers had a room-temperature mobility close to 1400 cm2/(Vs). AlYN/GaN heterostructures may offer advantages over AlScN/GaN heterostructures not only for the lower price and higher abundance of the raw material but also in terms of electrical characteristics and may be more suitable for power amplifying applications due to increased electron mobility.

Unraveling the impact of phosphate doping on surface properties and catalytic activity of gold supported on mixed iron-niobium oxide in gas phase methanol oxidation

In recent decades, there has been notable interest in understanding the influence of the support composition on the reactivity of gold species in oxidation processes. This study fits in with this scientific trend and investigates the effects of incorporating phosphate ions into Au catalysts supported on mixed iron-niobium oxides in methanol oxidation. All materials were thoroughly characterized using XRD, ICP-OES, DR-UV-Vis, N2 physisorption, HRTEM, HAADF-STEM, SEM-EDX, XPS, TPD-NH3, TPD-CO2, and in situ FTIR combined with adsorption of NO. Activity of the catalysts was evaluated using a fixed-bed flow reactor combined with gas chromatography and operando FTIR-MS system. It was observed that the phosphate-doped catalyst supported on mixed Fe-Nb oxide exhibited significantly higher activity than phosphate-free sample. This improvement resulted from increased electron mobility, enhanced acidity, and optimized distribution of gold nanoparticles on the former catalyst. Knowledge resulting from this work can lead to the development of more efficient gold catalysts.

Microscopic effect of iron dosage on the stability of Fe‐doped ettringite

AbstractOne significant aspect that affects the performance of high‐ferrite cement is the incorporation of iron (Fe) atoms and its stabilization into the cement phases. However, the influence of Fe doping on the stability of key phases, particularly on the ettringite, remains largely unexplored requiring deeper insights into the fundamental mechanisms. The present study explored the stability of Fe‐doped AFt structure based on density functional theory calculations at different Fe dosage. The obtained results showed that the stability of AFt structure decreases by increasing Fe dosage, which is in good agreement with the previous experimental observations. The incorporation of Fe into ettringite induced a series of changes in AFt structural and electronic properties. Bond order analysis underscored stronger covalent Fe–O bonds compared to Al–O, further emphasizing changes in the material's bonding network. Notably, density of states (DOS) analysis highlights the emergence of new occupied states near the Fermi level, primarily contributed by Fe and O atoms. This increased DOS, coupled with higher electron mobility, correlates with a reduction in material stability, as observed through shifts in bonding interactions and alterations in the bonding network. These findings point toward a complex interplay of factors, including altered bonding characteristics, increased electron mobility, and changes in the electronic structure, contributing to the observed instability of Fe‐doped ettringite.

Aqueous inks for ecofriendly processing of organic solar cells: Investigation of morphological changes

Aqueous dispersions of organic semiconducting nanoparticles (NPs) are particularly attractive as inks for the environmentally friendly preparation of organic solar cells. The internal morphology of the NPs, which depends on their elaboration process, is a key parameter, which has a significant influence on the final morphology of the active layer and therefore its effectiveness. In the present study, core-shell (PF2:PC71BM) NPs were prepared by miniemulsion. Their internal morphology including the composition of the two phases was characterized by scanning transmission X-ray microscopy (STXM) showing a core composed of 77% PC71BM and a shell composed of 75% PF2. It was found that thermal annealing promotes PC71BM diffusion from the core to the shell, increasing its proportion in the shell from 25% to 42%. This annealing, when applied after NPs deposition by spincoating, allows partial coalescence of the NPs, reducing the roughness of the active layer, and increases electron mobility, thus demonstrating the formation of PC71BM percolation paths for electron transport. A PCE of 1.6% could thus be obtained after 10 min of thermal annealing at 100°C. At higher temperature, Grazing-Incidence Wide-Angle X-Ray Scattering (GIWAXS) analyses demonstrate the modification of the PF2 structuration from randomly oriented lamella after deposition to edge-on orientation after annealing, leading to an unfavorable decrease of the hole mobility in the direction perpendicular to the substrate, while increasing the hole mobility in the substrate plane. This study demonstrates the need to systematically characterize the internal morphology of NPs in order to rationalize the morphology of the active layer and optimize its properties.

Aqueous solution processed transition-metal-doped ZnO as electron injection layers for efficient inverted organic light emitting diodes

Zinc oxide (ZnO) has attracted lots of attention to be used as interfacial materials in organic optoelectronic devices owing to its attractive properties. In this work, a series of transition-metal-doped ZnO thin films were prepared by using a facile aqueous solution process, thereafter these films were employed as electron injection layers (EILs) combined with the tris-(8-hydroxyquinoline) aluminum (Alq3) emitting layer to construct the inverted organic light-emitting diodes (IOLEDs). The transition-metal-doped ZnO EIL-based IOLEDs demonstrate markedly improved device performance compared to the reference neat ZnO EIL-based IOLED. However, different transition-metal ions have much different doping effect on the device performance. CoCl2 doped ZnO EIL based IOLED device possesss an optimal current efficiency of 5.52 cd A−1, which is increased about 40% compared to the device with the neat ZnO as EIL. The enhancement might be attributed to the increased electron mobility and favorable interfacial energy level alignment of the transition-metal doped ZnO EIL for more efficient electron injection. Our findings may provide a promising strategy to improve the electron injection properties of ZnO film in the OLED devices.

Tailoring of Visible to Near-Infrared Active 2D MXene with Defect-Enriched Titania-Based Heterojunction Photocatalyst for Green H2 Generation.

A wide solar light absorption window and its utilization, long-term stability, and improved interfacial charge transfer are the keys to scalable and superior solar photocatalytic performance. Based on this objective, a noble metal-free composite photocatalyst is developed with conducting MXene (Ti3C2) and semiconducting cauliflower-shaped CdS and porous Cu2O. XPS, HRTEM, and ESR analyses of TiOy@Ti3C2 confirm the formation of enough defect-enriched TiOy (where y is < 2) on the surface of Ti3C2 during hydrothermal treatment, thus creating a third semiconducting site with enough oxygen vacancy. The final material, TiOy@Ti3C2/CdS/Cu2O, shows a broad absorption window from 300 to 2000 nm, covering the visible to near-infrared (NIR) range of the solar spectrum. Photocatalytic H2 generation activity is found to be 12.23 and 16.26 mmol g-1 h-1 in the binary (TiOy@Ti3C2/CdS) and tertiary composite (TiOy@Ti3C2/CdS/Cu2O), respectively, with good repeatability under visible-NIR light using lactic acid as the hole scavenger. A clear increase of efficiency by 1.53 mmol g-1 h-1 in the tertiary composite due to NIR light absorption supports the intrinsic upconversion of electrons, which will open a new prospective of solar light utilization. Decreased charge-transfer resistance from the EIS plot and a decrease in PL intensity established the improved interfacial charge separation in the tertiary composite. Compared to pure CdS, H2 generation efficiency is 29.6 times higher on the noble metal-free tertiary composite with an apparent quantum efficiency of 12.34%. Synergistic effect of defect-enriched TiOy formation, creation of proper dual p-n junction on a Ti3C2 sheet as supported by the Mott-Schottky plot, significant NIR light absorption, increased electron mobility, and charge transfer on the conductive Ti3C2 layer facilitate the drastically increased hydrogen evolution rate even after several cycles of repetition. Expectantly, the 2D MXene-based heterostructure with defect-enriched dual p-n junctions of desired interface engineering will facilitate scalable photocatalytic water splitting over a broad range of the solar spectrum.

Elucidating the effects of the sidechain substitution direction on the optoelectronic properties of isomeric diketopyrrolopyrrole-based conjugated polymers for near-infrared organic phototransistors

Compared to P3BT-out, P3BT-in with sidechains in the inner way has better molecular planarity, narrower bandgap, and stronger light absorption ability, resulting in an increased electron mobility and higher near-infrared photoresponsivity.

Highly stable two-dimensional α1-MA2Z4 (M = Mg, Ca, Sr; A = Al; Z = S, Se) monolayers with promising photocatalysis and piezoresistive effect

The fundamental properties of two-dimensional α1-MA2Z4 (M = Mg, Ca, Sr; A = Al; Z = S, Se) monolayers have been systematically investigated based on the first principles calculations. Our results show that the α1-MA2Z4 monolayers have mixed ionic-covalent bonding character. The structural stability analyses reveal that all structures are dynamically stable and sustain stability below 800 K. All α1-MA2Z4 monolayers exhibit semiconducting property. The suitable bandgaps and the band edges alignment strides the redox potentials of water splitting, having potential as the candidates of the photocatalyst. All structures are predicted to possess isotropic electron-dominated mobility, which increases from 340.79 to 591.84 cm2 s−1 V−1 with the increase in atomic number of the alkaline-earth metal and chalcogen group. Further imposing the strain along the armchair direction, the electron mobility of α1-MA2Z4 can be enhanced to ∼103 cm2 V−1 s−1, especially the electron mobility of α1-MgA2S4 even increases to ∼2 × 103 cm2 V−1 s−1. The increased electron mobility indicates the reduced resistivity, which shows that the α1-MA2Z4 monolayers possess a remarked piezoresistive effect. The outstanding properties indicate that the α1-MA2Z4 is promising in photocatalysis and flexible electronics fields.

G-C3N4/Chlorocobaloxime Nanocomposites as Multifunctional Electrocatalysts for Water Splitting and Energy Storage.

Due to environmental contamination and the depletion of energy supplies, it is very important to develop low-cost, high-performance, multifunctional electrocatalysts for energy conversion and storage systems. Herein, we report the development of cost-effective modified electrodes containing g-C3N4/chlorocobaloxime composites (C1-C4) and their electrocatalytic behavior toward the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER), followed by their energy-storage applications. A series of chlorocobaloximes {ClCo(dpgH)2B} with diphenylglyoxime (dpgH) and neutral bases (B) containing a carboxylic acid moiety (isonicotinic acid, pyridine-3,5-dicarboxylic acid, indole-2-carboxylic acid, and p-aminobenzoic acid) have been synthesized and characterized by spectroscopic techniques. The nanocomposites of g-C3N4/chlorocobaloximes are prepared and characterized by Fourier transform infrared (FTIR) spectroscopy, ultraviolet-visible diffuse reflectance spectroscopy (UV-DRS), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), X-ray photoelectron spectroscopy (XPS), particle size distribution analysis (PSA), Brunauer-Emmett-Teller (BET), and energy dispersive X-ray analysis (EDAX) techniques. The composite coatings exhibit enhanced HER performance at lower overpotential and with a lower Tafel slope. When the water-splitting reactions are studied using 0.5 M H2SO4 and 0.5 M KOH as electrolytic solutions, the composite g-C3N4/C2 containing pyridine-3,5-dicarboxylic acid as a neutral base shows excellent HER activity with a lower overpotential of 173 mV at -10 mA cm-2 and OER activity with a lower overpotential of 303 mV. The HER reaction takes place through the Volmer-Heyrovský mechanism, where the desorption step is the rate-determining step. Among the synthesized nanocomposites, the nanocomposite g-C3N4/C2 shows higher efficiency toward both HER and OER reactions, with a lower Tafel slope of 55 mV dec-1 for HER and 114 mV dec-1 for OER than the other nanocomposites. The overall water-splitting studies of the composite g-C3N4/C2 in 0.5 M KOH indicate that the evolution of hydrogen and oxygen occurs constantly up to 120 h. The supercapacitance applications studied using cyclic voltammetry and charge-discharge studies indicate that the nanocomposite g-C3N4/C1 shows a good specific capacitance of 236 F g-1 at 0.5 A g-1 compared to others. The increased electrochemical performance of the synthesized nanocomposites is due to the incorporation of electron-withdrawing carboxylic-acid-functionalized neutral bases present in cobaloximes, which increases electron mobility. The incorporation of a cobaloxime complex into a g-C3N4 nanosheet enhances the electrocatalytic behavior of the nanosheet, and its performance can further be fine-tuned by systematic variation in the structure of cobaloxime by changing the halide ion, dioxime, the neutral base ligand, or the substituent.

Attaining High Figure of Merit in the N-Type Bi2Te2.7Se0.3-Ag2Te Composite System via Comprehensive Regulation of Its Thermoelectric Properties.

n-Type Bi2Te2.7Se0.3 (BTS) is the state-of-the-art thermoelectric material near room temperature. However, the figure of merit ZT of commercial BTS ingots is still limited and further improvement is imperative for their wide applications. Here, the results show that through dispersion of the Ag2Te nanophase in BTS, one can not only elevate its power factor (PF) by as high as 14% (at 300 K) but also reduce its thermal conductivity κtot to as small as ∼29% (at 300 K). Experimental evidences show that the improved PF comes from both increased electron mobility via inhibited Te vacancies and enhanced thermopower due to energy filtering effect, while the reduction of κtot originates from the drop of both electronic thermal conductivity largely owing to the reduced number of vacancy VTe·· and intensified phonon scattering chiefly from the dispersed Ag2Te nanophase. Consequently, the largest ZTmax = 1.31 (at 350 K) and average ZTave = 1.16 (300-500 K) are achieved for the Bi2Te2.7Se0.3-0.3 wt % Ag2Te composite sample, leading to a projected conversion efficiency η = 8.3% (300-500 K). The present results demonstrate that incorporation of nanophase Ag2Te is an effective approach to boosting the thermoelectric performance of BTS.

Asymmetric perylene-diimide-based polymeric acceptor integrating alkoxy and alkyl side chains: Synthesis and application for all-polymer solar cell

Alkoxy side chain embodying the large electronegative oxygen played the critical role in tuning the optoelectronic and photovoltaic properties. However, few efforts devoted to incorporating the alkoxy side chain into perylene diimide (PDI) building block. In this contribution, one PDI-containing asymmetric polymeric acceptor PPDI-HD-OHD-T bearing 2-hexyldecyl (HD) and 2-hexyldecyloxy (OHD) side chains was developed. Also, two symmetric polymeric acceptors PPDI-HD2-T and PPDI-OHD2-T with identical HD and OHD side chains were prepared to systematically study the impact of bonding OHD side chain on light-harvesting and electrochemical property, molecular configuration, solar cell performance and morphology. Moving from alkyl to alkoxy chains resulted in at first a red-shifted and then a blue-shifted absorption maximum, gradually downshifted HOMO and LUMO energy levels, better molecular planarity, enhanced solution and film state aggregation, and improved photo-stability, these changes resulted from the N–O σ-inductive effect induced by the inserted oxygen, along with the increased number of alkoxy side chain of PDI ring. Furthermore, PPDI-HD-OHD-T acquired a more complementary absorption to PTB7-Th, increased electron mobility and benefited morphology. Thereupon, both improved JSC and FF in PPDI-HD-OHD-T-based device contributed to the boosted PCE of 2.08%, which was higher than those of symmetric side chains PPDI-HD2-T and PPDI-HD-OHD-T-based devices. To our knowledge, it is the first attempt to introduce the alkoxy side chain to N-position of PDI to construct asymmetric polymer acceptor and demonstrated that skillfully tuning the side-chain can effectively affect the electron distribution, molecular configuration, aggregation, charge mobility, and achieve improved device efficiency in all-polymer solar cell.

Recent advancement in doped vanadium pentoxide for energy storage devices

The search for high-performing supercapacitors is a major area of energy storage and conversion research due to the increasing demand for portable electronics, electric vehicles, and green energy solutions. To improve upon traditional batteries and capacitors, researchers have focused on designing different electrode materials made of vanadium pentoxide (V2O5), which has a high capacitive potential and is non-toxic. However, poor conductivity, low porosity, and charge/discharge dissolution limit the performance of bulk V2O5. To overcome these limitations, researchers have added dopants to V2O5, which increase electron mobility, surface area, and structural stability. This review focuses on the effects of different synthesis methods and physical treatment strategies on the structure and electrochemical performance of doped V2O5 electrodes.

Homoepitaxial GaN terahertz planar Schottky barrier diodes

In this work, a new type of terahertz Schottky barrier diode (SBD) based on homoepitaxial gallium nitride (GaN) was fabricated for high-power and high-frequency multiplier applications. The measured full width at half maximum of x-ray diffraction peaks for homoepitaxial GaN (002) and (102) plane is only one third of the heteroepitaxial GaN on sapphire substrate. Additionally, the increased electron mobility in both n−/n+ GaN epitaxial layers, induced by improved material quality, can effectively reduce the epitaxial resistance (R epi) and the spreading resistance. As a result, the total series resistance of the fabricated GaN SBD is 13.7 Ω, which is only 65% of that of heteroepitaxial GaN on a sapphire substrate. Additionally, the cut-off frequency (f c) is improved to 1.61 THz at zero bias voltage and the measured breakdown voltage is 16.17 V at −1 μA.

WSe2/g-C3N4 for an In Situ Photocatalytic Fenton-like System in Phenol Degradation.

An in situ photo-Fenton system can continuously generate H2O2 by photocatalysis, activating H2O2 in situ to form strong oxidizing ·OH radicals and degrading organic pollutants. A WSe2/g-C3N4 composite catalyst with WSe2 as a co-catalyst was successfully synthesized in this work and used for in situ photo-Fenton oxidation. The WSe2/g-C3N4 composite with 7% loading of WSe2 (CNW2) has H2O2 production of 35.04 μmol/L, which is fourteen times higher than pure g-C3N4. The degradation efficiency of CNW2 for phenol reached 67%. By constructing an in situ Fenton-system, the phenol degradation rate could be further enhanced to 90%. WSe2 can enhance the catalytic activity of CNW2 by increasing electron mobility and inhibiting the recombination of photogenerated electron–hole pairs. Moreover, the addition of Fe2+ activates the generated H2O2, thus increasing the amount of strong oxidative ·OH radicals for the degradation of phenol. Overall, CNW2 is a promising novel material with a high H2O2 yield and can directly degrade organic pollutants using an in situ photo-Fenton reaction.

Dual-functional PANI/MIL-125(Ti) photoanodes for enhanced photoelectrochemical H2 generation and photothermal heating

MIL-125(Ti) metal-organic framework coated with HCl doped conducting polyaniline (PANI) photocatalyst (PANI/MIL-125(Ti)) was fabricated for photoelectrochemical (PEC) hydrogen production under visible LED illumination. PANI coating not only decreased the band gap of MIL-125(Ti), but also increased electron mobility of the overall structure due to its π-conjugated structure that provided a remarkable increase in current density, reaching to 6.55 mA/cm2 (at 1.23 V vs. RHE) under visible LED irradiation. Furthermore, the applied bias photon-to-current efficiency (ABPE) revealed that the highest ABPE value (2.36%) was found for PANI/MIL-125(Ti) photoanodes (under LED illumination at 1.01 V vs RHE). These superior PEC H2 evolution performance strongly imply the role of PANI as a hole-transporter upon visible LED irradiation for efficient charge separation and reduced electron hole recombination with prolonged life time using PANI/MIL-125(Ti) photoanodes. Besides, the noteworthy photothermal power conversion efficiency (PCE = 79.3%) provides a unique platform to enhance the energy-conversion in the fields of photocatalysis, energy storage, and photothermal applications.

Efficient All-Polymer Solar Cells with Sequentially Processed Active Layers.

In this work, we apply the sequential processing (SqP) method to address the relatively low electron mobility in recent all-polymer solar cells (all-PSCs) based on the polymerized small-molecule acceptor (PSMA). Compared to the blend-casting (BC) method, all-PSCs composed of PM6/PY-IT via the SqP method show boosted electron mobility and a more balanced charge carrier transport, which increases the FF of the SqP device and compensates for the short-circuit current loss, rendering comparable overall performance with the BC device. Through film-depth-dependent light absorption spectroscopy, we analyze the sub-layer absorption and exciton generation rate in the vertical direction of the device, and discuss the effect of the increased electron mobility on device performance, accordingly.

A New Alcohol‐Soluble Polymer PFN‐ID as Cathode Interlayer to Optimize Performance of Conventional Polymer Solar Cells by Increasing Electron Mobility

A new alcohol‐soluble polymer PFN‐ID is successfully synthesized by combining N,N‐di(2‐ethylhexyl)‐6,6′‐dibromoisoindigo and an amino‐containing fluorene subunits, and applied to polymer solar cells (PSCs) with PTB7‐Th:PC71BM as an active layer. The n‐type backbone of the PFN‐ID improves electron transfer performance and thus optimizes device performance. The PSCs with PFN‐ID as cathode interfacial layers (CILs) have significantly improved compared to the device without the interface layer, especially the optimum power conversion efficiency (PCE) of PSCs reaches up to 9.24%, which is 1.62 times higher than that of devices without CILs. The I–V curves show that the introduction of the n‐type backbone leads to a significant increase in the conductivity of PFN‐ID compared to PFN. The UV photoelectron spectroscopy and Mott–Schottky curves further confirm that PFN‐ID can decrease the work function of Al electrode, and increase its built‐in potential, giving higher open‐circuit voltage. The resulting conventional PSCs using PFN‐ID as cathode interlayer achieve high photovoltaic performance, and the research results can provide a new strategy for the advancement of PSCs.

W:BiVO4-WO3-V2O5 heterostructures increase light absorption and charge transport in photoanodes for water splitting

Efficient light absorption and charge separation and transfer are the main obstacles that still need to be addressed to increase the performance of photoanodes for the water oxidation reaction. Here, we show that the combination of W:BiVO4, WO3, and V2O5 can simultaneously improve light absorption and the separation and transport of electrons and holes in the photoanode and consequently its photoelectrochemical performance for the water oxidation reaction. The high photoelectrochemical activity of the photoanode is due to the different bandgap energies of W:BiVO4 (2.44 eV), WO3 (2.90 eV), and V2O5 (2.27 eV), which provide higher absorption of visible light and improved charge transport in the heterojunction: V2O5 facilitates the transport of holes while WO3 increases electron mobility. As a result, the W:BiVO4-WO3-V2O5 photoanode produces a photocurrent density as high as 8.2 mA cm−2 at 1.23 V vs. RHE in sodium sulfate electrolyte (pH 6.96). By modifying the surface of the W:BiVO4-WO3-V2O5 photoanode with an electrocatalyst for water oxidation, the photocurrent can reach 12.1 mA cm−2. Thus, the multiple ternary heterojunctions of W:BiVO4-WO3-V2O5 proved an efficient strategy for producing high-performance photoanodes for photoelectrochemical applications.

Tunable vertical ferroelectricity and domain walls by interlayer sliding in \u03b2-ZrI2

Vertical ferroelectricity where a net dipole moment appears as a result of in-plane ionic displacements has gained enormous attention following its discovery in transition metal dichalcogenides. Based on first-principles calculations, we report on the evidence of robust vertical ferroelectricity upon interlayer sliding in layered semiconducting β-ZrI2, a sister material of polar semimetals MoTe2 and WTe2. The microscopic origin of ferroelectricity in ZrI2 is attributed to asymmetric shifts of electronic charges within a trilayer, revealing a subtle interplay of rigid sliding displacements and charge redistribution down to ultrathin thicknesses. We further investigate the variety of ferroelectric domain boundaries and predict a stable charged domain wall with a quasi-two-dimensional electron gas and a high built-in electric field that can increase electron mobility and electromechanical response in multifunctional devices. Semiconducting behaviour and a small switching barrier of ZrI2 hold promise for various ferroelectric applications, and our results provide important insights for further development of slidetronics ferroelectricity.