Epitaxial Growth of 2D Bi2O2Se Nanoplates/1D CsPbBr3 Nanowires Mixed-Dimensional Heterostructures with Enhanced Optoelectronic Properties

The 2D/1D mixed-dimensional van der Waals heterostructures have great potential for electronics and optoelectronics with high performance and multifunctionality. The epitaxy of 1D micro/nanowires on 2D layered materials may efficiently realize the large-scale preparation of 2D/1D heterostructures, which is critically important for their practical applications. So far, however, only the wires of Bi₂S₃, Te, and Sb₂Se₃ have been epitaxially grown on MoS₂ or WS₂. Here, it is reported that the epitaxial growth of 1D CsPbBr₃ nanowires on 2D Bi₂O₂Se nanoplates through a facile vertical vapor deposition method. The CsPbBr₃ wires are well aligned on the Bi₂O₂Se plates in fourfold symmetry with the epitaxial relationships of [001]_CsPbBr3||[200]_Bi2O2Se and [1-10]_CsPbBr3||[020]_Bi2O2Se. The photoluminescence results reveal that the emission from CsPbBr₃ is significantly quenched in the heterostructure, which implies the charge carriers transfer from CsPbBr₃ to Bi₂O₂Se. The waveguide characterization shows that the epitaxial CsPbBr₃ wires may efficiently confine and guide their emission, which favors the light absorption of Bi₂O₂Se. Importantly, the photocurrent mapping and spectra of the devices based on these 2D/1D heterostructures prove that the epitaxial CsPbBr₃ wires remarkably enhances the photoresponse of Bi₂O₂Se, which indicates these heterostructures can be applied in high-performance optoelectronic devices or on-chip integrated photonic circuits.     

Controlled Vapor–Solid Deposition of Millimeter‐Size Single Crystal 2D Bi2O2Se for High‐Performance Phototransistors

Atomically thin 2D materials have received intense interest both scientifically and technologically. Bismuth oxyselenide (Bi₂O₂Se) is a semiconducting 2D material with high electron mobility and good stability, making it promising for high‐performance electronics and optoelectronics. Here, an ambient‐pressure vapor–solid (VS) deposition approach for the growth of millimeter‐size 2D Bi₂O₂Se single crystal domains with thicknesses down to one monolayer is reported. The VS‐grown 2D Bi₂O₂Se has good crystalline quality, chemical uniformity, and stoichiometry. Field‐effect transistors (FETs) are fabricated using this material and they show a small contact resistivity of 55.2 Ω cm measured by a transfer line method. Upon light irradiation, a phototransistor based on the Bi₂O₂Se FETs exhibits a maximum responsivity of 22 100 AW^?1, which is a record among currently reported 2D semiconductors and approximately two orders of magnitude higher than monolayer MoS₂. The Bi₂O₂Se phototransistor shows a gate tunable photodetectivity up to 3.4 × 10¹⁵ Jones and an on/off ratio up to ≈10⁹, both of which are much higher than phototransistors based on other 2D materials reported so far. The results of this study indicate a method to grow large 2D Bi₂O₂Se single crystals that have great potential for use in optoelectronic applications.     

Broadband Bi2O2Se Photodetectors from Infrared to Terahertz

2D Bi₂O₂Se has shown great potential in photodetector from visible to infrared (IR) owing to its high mobility, ambient stability, and layer-tunable bandgaps. However, for the terahertz (THz) band with longer wavelength and richer spectral information, there are few reports on the research of THz detection based on 2D materials. Herein, an antenna-assisted Bi₂O₂Se photodetector is constructed to achieve broadband photodetection from IR to THz ranges driven by multi-mechanism of electromagnetic waves to electrical conversion. The good tradeoff between the bandgap and high mobility results in a broad spectral detection. In the IR region, the nonequilibrium carriers result from photo-induced electron-hole pairs in the Bi₂O₂Se body. While in the THz region, the carriers are caused by the injected electrons from the metal electrodes by the electromagnetic-induced well. The Bi₂O₂Se photodetector achieves a broadband responsivity of 58 A W^-1 at 1550 nm, 2.7 × 10⁴ V W^-1 at 0.17 THz, and 1.9 × 10⁸ V W^-1 at 0.029 THz, respectively. Surprisingly, an ultrafast response time of 476 ns and a quite low noise equivalent power of 0.2 pW Hz^−1/2 are acquired at room temperature. Our researches exhibit promising prospects of Bi₂O₂Se in broadband detection, THz imaging, and ultrafast sensing.     

Silver Ions Assisted Inversion Temperature Crystallization of 2D Cs3Bi2Br9 Nanoflakes for Highly Sensitive X-Ray Detection

2D perovskites have attracted wide attention for optoelectronic applications because of their unique layer structure and tunable outstanding optical/electrical properties. In addition, 2D Cs₃Bi₂Br₉ nanoflakes possess large effective atomic number, high resistivity, high density as well as excellent stability, rendering it a promising material for X-ray detection. Nevertheless, it is full of challenges to synthesize 2D Cs₃Bi₂Br₉ nanoflakes by conventional inversion temperature crystallization (ITC) strategy due to the existence of Br^- vacancies in the Cs₃Bi₂Br₉ crystal nucleus. Herein, an Ag⁺ assisted ITC (SAITC) strategy to grow 2D Cs₃Bi₂Br₉ nanoflakes is proposed. The synthesis mechanism revealed by both experiments and theoretical calculations can be mainly ascribed to the passivated Br⁻ vacancies and enhanced structure stability by adding Ag⁺ which can effectively prevent the oxidation of 2D Cs₃Bi₂Br₉ nanoflakes from growth of hybrid crystals. The synthesized high-crystallinity 2D Cs₃Bi₂Br₉ nanoflakes possess direct bandgap characteristic, and the mobility lifetime can reach 9.8 × 10⁻⁴ cm² V⁻¹. Excitingly, the fabricated device based on 2D Cs₃Bi₂Br₉ nanoflakes demonstrates ultrahigh sensitivity of detecting X-ray (1.9 CGy_air⁻¹cm⁻²) at very low driven voltage (0.5 V) due to the photoconductive gain mechanism. The 2D Cs₃Bi₂Br₉ nanoflakes synthesized by SAITC method have great potential for developing highly sensitive optoelectronic devices.     

Out-of-Plane Resistance Switching of 2D Bi2O2Se at the Nanoscale

Two-dimensional (2D) bismuth oxyselenide (Bi₂O₂Se) with high electron mobility shows great potential for nanoelectronics. Although the in-plane properties of Bi₂O₂Se have been widely studied, its out-of-plane electrical transport behavior remains elusive, despite its importance in fabricating devices with new functionality and high integration density. Here, the out-of-plane electrical properties of 2D Bi₂O₂Se at nanoscale are revealed by conductive atomic force microscope. This work finds that hillocks with tunable heights and sizes are formed on Bi₂O₂Se after applying a vertical electric field. Intriguingly, such hillocks are conductive in the vertical direction, resulting in a previously unknown out-of-plane resistance switching in thick Bi₂O₂Se flakes while ohmic conductive characteristic in thin ones. Furthermore, the transformation is observed from bipolar to stable unipolar conduction in thick Bi₂O₂Se flake possessing such hillocks, suggesting its potential to function as a selector in vertical devices. This work reveals the unique out-of-plane transport behavior of 2D Bi₂O₂Se, providing the basis for fabricating vertical devices based on this emerging 2D material.     

Polar Layered Bismuth-Rich Oxyhalide Piezoelectrics Bi4O5X2 (XBr,I): Efficient Piezocatalytic Pure Water Splitting and Interlayer Anion-Dependent Activity

Piezocatalytic pure water splitting for H₂ evolution carries the virtues of efficacious utilization of mechanical energy, easy operation, and high value-added products, while lacking desirable piezoelectrics for high chemical energy production. Here, two polar layered bismuth-rich oxyhalides Bi₄O₅X₂ (XBr, I) thin nanosheets (≈4 nm) are first exploited as efficient piezocatalysts to be capable of dissociating pure water. The unique asymmetrical layered structures of Bi₄O₅X₂ (XBr, I) composed of the interleaved [Bi₄O₅]²⁺ layer and double X⁻ ions slabs along the [1 0 1_] orientation cause large intrinsic dipole moment, excellent piezoelectricity and easy deformation. Without any cocatalyst and sacrificial agent, Bi₄O₅Br₂ and Bi₄O₅I₂ thin nanosheets display remarkable piezocatalytic H₂ production rate of 1149.0 and 764.5 µmol g⁻¹ h⁻¹, respectively, standing among the best piezocatalysts, accompanied by H₂O₂ and hydroxyl radicals (·OH) as oxidative products. The smaller radius and higher electronegativity of interleaved Br than I cause a more strongly polar crystal structure in Bi₄O₅Br₂, contributing to the higher piezocatalytic activity compared to Bi₄O₅I₂. This study broadens the scope of piezoelectric materials applied to sustainable energy catalysis by efficiently converting mechanical energy and illustrates the importance of crystal configuration and composition in fabricating efficient piezocatalytic systems.     

Catalyst-Free Growth of Atomically Thin Bi2O2Se Nanoribbons for High-Performance Electronics and Optoelectronics

1D materials have attracted significant research interest due to their unique quantum confinement effects and edge-related properties. Atomically thin 1D nanoribbons are particularly interesting because it is a valuable platform with the physical limits of both thickness and width. Here, a catalyst-free growth method is developed and the growth of Bi₂O₂Se nanostructures with tunable dimensionality is achieved. Significantly, Bi₂O₂Se nanoribbons with a thickness down to 0.65 nm, corresponding to a monolayer, are successfully grown for the first time. Electrical and optoelectronic measurements show that Bi₂O₂Se nanoribbons possess decent performance in terms of mobility, on/off ratio, and photoresponsivity, suggesting their promise for devices. This work not only reports a new method for the growth of atomically thin nanoribbons but also provides a platform to study properties and applications of such nanoribbon materials at a thickness limit.     

High‐Performance Near‐Infrared Photodetector Based on Ultrathin Bi2O2Se Nanosheets

As an emerging 2D layered material, Bi₂O₂Se has shown great potential for applications in thermoelectric and electronics, due to its high carrier mobility, near‐ideal subthreshold swing, and high air‐stability. Although Bi₂O₂Se has a suitable band gap for infrared (IR) applications, its photoresponse properties have not been investigated. Here, high‐quality ultrathin Bi₂O₂Se sheets are synthesized via a low‐pressure chemical vapor deposition method. The thickness of 90% Bi₂O₂Se sheets is below 10 nm and lateral sizes mainly distribute in the range of 7–11 µm. In addition, it is found that triangular sheets largely lack “O” content, even only 0.2 for Bi₂O_0.2Se. The near‐IR photodetection performance of Bi₂O₂Se nanosheets is systematically studied by variable temperature measurements. The response time, responsivity, and detectivity can approach up to 2.8 ms, 6.5 A W^?1, and 8.3 × 10¹¹ Jones, respectively. Additionally, the critical performance parameters, including responsivity, rising time, and decay time, remain at almost the same level when the temperature is changed from 80 to 300 K. These phenomena are likely due to the fact that as‐grown ultrathin Bi₂O₂Se sheets have no surface trap states and shallow defect energy levels. The findings indicate ultrathin Bi₂O₂Se sheets have great potentials for future applications in ultrafast, flexible near‐IR optoelectronic devices.     

Vacancy-Defect Topological Insulators Bi2Te3−x Embedded in N and B Co-Doped 1D Carbon Nanorods Using Ionic Liquid Dopants for Kinetics-Enhanced Li–S Batteries

Lithium–sulfur (Li–S) batteries are hindered by the shuttle effect and the sluggish redox kinetics of polysulfides. In this study, topological insulators (TIs) Bi₂Te_3−x with abundant Te vacancies embedded in N and B co-doped carbon nanorods (Bi₂Te_3−x@NBCNs) are synthesized and used as sulfur host composites for high-performance Li–S batteries. Bi₂Te_3−x@NBCNs effectively enhance the intrinsic conductivity, strengthened the chemical affinity, and accelerated the redox kinetics of polysulfides. 1D carbon nanorods with N and B co-doped heteroatoms endowed with abundant polar sites improve the chemical affinity of polysulfides, while the embedded Bi₂Te_3−x nanoparticles further promote the nucleation and electrodeposition of Li₂S₂/Li₂S. In situ Raman spectroscopy confirms that Bi₂Te_3−x@NBCNs effectively reduced cathode-side accumulation of polysulfides and suppressed the shuttle effect. Owing to the extraordinary synergistic effects of rich heteroatom polar sites and conductive topological surface states, Bi₂Te_3−x@NBCN-based cells exhibit a high initial specific capacity of 1264 mAh g⁻¹ at 0.2 C and ultra-long lifetime (>1000 cycles, with a degradation rate of 0.02% per cycle at 1.0 C). The fundamental insights offered by this work are likely to enable improvement of the electrochemical performance of Li–S batteries based on TI materials.     

Effect of Se content on the structural,morphological and optical properties of Bi2Te3−ySey thin films electrodeposited by under potential deposition technique

Bi₂Te_3−ySe_y thin films with different Se contents ranging from 0.3 to 2.5 were successfully electrodeposited by under potential deposition (UPD) technique onto gold foil substrates from an electrolyte consist of Bi(NO₃)₃, TeO₂, and SeO₂ at ambient conditions. The effects of Se content on structural, morphological and optical properties of the products were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and FT-IR spectroscopy, respectively. The XRD analysis revealed that the diffraction peaks positions of Bi₂Te_3−ySe_y thin films shifts gradually towards the higher angle side due to replacement of Te by Se atoms in the crystal structure with increasing Se content. The SEM results showed that the particle size of Bi₂Te_3−ySe_y thin films decreased as the Se content increased. The optical constants of ternary Bi₂Te_3−ySe_y thin films such as refractive index, extinction coefficient, and dielectric constant were obtained from the transmission spectra in the range of 2500–10.000 nm. The direct allowed band gap energies were estimated using Tauc equation and found to increase from 0.210 to 0.282 eV with increasing Se content from 0.3 to 2.5. The dispersion behavior of refractive index was studied by the single oscillator Wemple-DiDomenico model.     

Sensitive and Ultrabroadband Phototransistor Based on Two‐Dimensional Bi2O2Se Nanosheets

Bi₂O₂Se, a high‐mobility and air‐stable 2D material, has attracted substantial attention for application in integrated logic electronics and optoelectronics. However, achieving an overall high performance over a wide spectral range for Bi₂O₂Se‐based devices remains a challenge. A broadband phototransistor with high photoresponsivity (R) is reported that comprises high‐quality large‐area ( ≈ 180 µm) Bi₂O₂Se nanosheets synthesized via a modified chemical vapor deposition method with a face‐down configuration. The device covers the ultraviolet (UV), visible (Vis), and near‐infrared (NIR) wavelength ranges (360–1800 nm) at room temperature, exhibiting a maximum R of 108 696 A W^?1 at 360 nm. Upon illumination at 405 nm, the external quantum efficiency, R, and detectivity (D*) of the device reach up to 1.5 × 10⁷%, 50055 A W^?1, and 8.2 × 10¹² Jones, respectively, which is attributable to a combination of the photogating, photovoltaic, and photothermal effects. The devices reach a ?3 dB bandwidth of 5.4 kHz, accounting for a fast rise time (τ_rise) of 32 µs. The high sensitivity, fast response time, and environmental stability achieved simultaneously in these 2D Bi₂O₂Se phototransistors are promising for high‐quality UV and IR imaging applications.     

Nanostructured β‐Bi2O3 Fractals on Carbon Fibers for Highly Selective CO2 Electroreduction to Formate

3D Bi₂O₃ fractal nanostructures (f‐Bi₂O₃) are directly self‐assembled on carbon fiber papers (CFP) using a scalable hot‐aerosol synthesis strategy. This approach provides high versatility in modulating the physiochemical properties of the Bi₂O₃ catalyst by a tailorable control of its crystalline size, loading, electron density as well as providing exposed stacking of the nanomaterials on the porous CFP substrate. As a result, when tested for electrochemical CO₂ reduction reactions (CO₂RR), these f‐Bi₂O₃ electrodes demonstrate superior conversion of CO₂ to formate (HCOO^?) with low onset overpotential and a high mass‐specific formate partial current density of ?52.2 mA mg^?1, which is ≈3 times higher than that of the drop‐casted control Bi₂O₃ catalyst (?15.5 mA mg^?1), and a high Faradaic efficiency (FE_HCOO^?) of 87% at an applied potential of ?1.2 V versus reversible hydrogen electrode. The findings reveal that the high exposure of roughened β‐phase Bi₂O₃/Bi edges and the improved electron density of these fractal structures are key contributors in attainment of high CO₂RR activity.     

Multiscale Designed Niobium Titanium Oxide Anode for Fast Charging Lithium Ion Batteries

Fast charging of lithium ion batteries is essential for next-generation energy-storage systems. However, the poor ionic and electronic transport of anodes with its rather high mass loading limits the practical applications of this technology. Herein, a multiscale design from niobium titanium oxide anode material to electrode structure is proposed for fast charging lithium ion batteries with a practical level of areal capacity (3 mAh cm⁻²). At the atomic scale, the introduction of oxygen vacancy and surface carbon coating enables niobium titanium oxide (TiNb₂O_7−x@C) to possess excellent ionic and electronic conductivity. For the microscopic electrode structure, 1D TiNb₂O_7−x@C fibers are tightly assembled to form a high-speed transport network of ions and electrons throughout the electrode. As a result, the obtained TiNb₂O_7−x@C electrode shows excellent rate capability (1.83 mAh cm⁻² at 1 C) and cycling stability under an areal capacity of 3 mAh cm⁻² (2.35 mAh cm⁻² after 100 cycles at 0.5 C) in half-cells. Significantly, a full-cell coupled with practical level mass loading of lithium cobalt oxide cathode is demonstrated to deliver 1.55 mAh cm⁻² at 3 C for the first time.     

Nanofluid Electrolyte with Fumed Al2O3 Additive Strengthening Zincophilic and Stable Surface of Zinc Anode toward Flexible Zinc–Nickel Batteries

Flexible zinc–nickel batteries (FZNBs) have been considered as a promising power supply for wearable electronics due to the intrinsic safety, high operating voltage and superior rate performance. However, the serious self-corrosion of zinc and the redistribution of dissolved [Zn(OH)₄]²⁻ on the electrode surface limit the electrochemical performance of FZNBs. Herein, the nanofluid electrolyte with fumed Al₂O₃ additive is introduced into FZNBs and a protective layer is formed due to the adsorption of Al₂O₃ on the electrodeposited zinc anode. The protective layer strengthens the zincophilicity of the anode and homogenizes the deposition of [Zn(OH)₄]²⁻, avoiding the dendrite formation and the shape change of electrode. Meanwhile, by suppressing the [Zn(OH)₄]²⁻ diffusion from the anode surface to the bulk electrolyte, the interface stabilization is effectively promoted, thereby improving zinc utilization rate and inhibiting the corrosion. Hence, the FZNBs assembled with Al₂O₃-nanofluid electrolyte and electrodeposited zinc anode demonstrates superior energy density of 210 Wh L⁻¹ with a stable cycling of 575 h. Furthermore, FZNBs modified with Al₂O₃-nanofluid electrolyte have a promising future in the field of wearable and portable electronics.     

Self-Driven WSe2/Bi2O2Se Van der Waals Heterostructure Photodetectors with High Light On/Off Ratio and Fast Response

Benefiting from the superior electron mobility and good air-stability, the emerging layered bismuth oxyselenide (Bi₂O₂Se) nanosheet has received considerable attention with the promising prospects for electronics and optoelectronics applications. However, the high charge carrier concentration and bolometric effect of Bi₂O₂Se give rise to the high dark current and relatively slow photoresponse, which severely impede further improvement of the performance of Bi₂O₂Se based photodetectors. Here, a WSe₂/Bi₂O₂Se Van der Waals p-n heterostructure is reported with a pronounced rectification ratio of 10⁵ and a low reverse dark current of 10⁻¹¹ A, as well as an enhanced light on/off ratio up to 618 under 532 nm light illumination. The device also exhibits a fast response speed of 2.6 µs and a broadband detection capability from 365 to 2000 nm due to the efficient charge separation and strong interlayer coupling at the interface of the two flakes. Importantly, the built-in potential in the WSe₂/Bi₂O₂Se heterostructure offers a competitive self-powered photodetector with the light on/off ratio above 10⁵ and a photovoltaic responsivity of 284 mA W⁻¹. The WSe₂/Bi₂O₂Se heterostructure shows promising potentials for high-performance self-driven photodetector applications.     

Carbon and silica interlayer influence for the photocatalytic performances of spindle-like α-Fe2O3/Bi2O3 p–n heterostructures

The p–n heterojunction is an effective structure to suppress the recombination of photogenerated charge carriers due to the built-in internal electric field. Herein, we successfully synthesize a spindle-like α-Fe₂O₃/Bi₂O₃ core–shell heterostructure, in which α-Fe₂O₃ is an n-type semiconductor and Bi₂O₃ is a p-type semiconductor. In comparison with pure α-Fe₂O₃ seeds, the α-Fe₂O₃/Bi₂O₃ p–n heterojunction photocatalyst exhibits tremendous photocatalytic performance on the degradation of Rhodamine B (RhB) under illumination of visible light. In addition, we insert an interlayer between p–n heterostructure, similar to p–i–n heterostructure. The silicon oxide and carbon are selected as the interlayer due to its different conductivity. The as-obtained α-Fe₂O₃/C/Bi₂O₃ exhibits higher degradation rate than α-Fe₂O₃/SiO₂/Bi₂O₃. The reason is attributed to the mesoporous structure of carbon layer and its high conductivity so that the photogenerated electrons can be easily transferred from the conduction band of α-Fe₂O₃ to the conduction band of Bi₂O₃ thereby promoting an effective separation of photogenerated electrons and holes. However, the introduction of interlayer reduces the photocatalytic activity due to the alteration of internal built-in electric field in the heterojunction. We envision that these results have potential applications for designing the heterostructural photocatalysts.     

Lattice Instability Induced Concerted Structural Distortion in Charged and van der Waals Layered GdTe3

Structural mosaic of rare-earth tri-tellurides (RTe₃) inlaid with non-classical structural motifs like the 2D−polytelluride square nets has attracted immense attention owing to their enigmatic chemical bonding, unconventional structure, and harboring charge density wave (CDW) ground states. GdTe₃, an archetypal RTe₃, is a natural heterostructure of charged and van der Waals (vdW) layers, formed by intercalating vdW gap separated 2D square telluride nets [(Te₂)⁻]_n between the charged double corrugated slabs of n[GdTe]⁺. Here, we have investigated the evolution of structural distortions along with the electrical and thermal transport properties of GdTe₃ across its CDW transition through X-ray pair distribution function analysis, thermal conductivity measurements, Raman spectroscopy and first principles theoretical calculations. The results reveal that the unusual structure of GdTe₃ engenders a large anisotropic lattice thermal conductivity by concomitantly hampering the phonon propagation along parallel to the spark plasma sintering (SPS) pressing direction via chemical bonding hierarchy while facilitating phonon propagation along perpendicular to the SPS pressing direction through the metallic Te sheets and phason channel. The low lattice thermal conductivity is attributed to the strong vibrational anharmonicity caused by CDW-induced concerted local lattice distortions of both Gd–Te slab and Te square net, and the robust electron–phonon coupling.     

Seed‐Induced Vertical Growth of 2D Bi2O2Se Nanoplates by Chemical Vapor Transport

As two‐dimensional (2D) layered materials attract more attention owing to their unique optical, electrical, and thermal properties, there are persistent efforts to grow high‐quality 2D layered materials for fundamental research and device applications. While large‐area 2D layered materials with high crystal quality can be obtained through chemical vapor transport, the strong binding between 2D layered materials and substrates poses a significant challenge for attempts to reveal their intrinsic properties and to use these 2D building blocks for constructing advanced heterostructured devices. Therefore, it would be ideal to grow high‐quality 2D materials with minimized contact and binding with substrate. Through both calculation and experiment, it is demonstrated that by introducing a seed layer at the nucleation stage, the crystallographic disregistry and the corresponding adhesion energy between 2D materials and substrate can be altered, resulting in a change of crystal surface in contact with the substrate, and therefore vertical growth of 2D materials on substrates. As an example, it is demonstrated that with Bi₂O₃ serving as a seed layer, vertical growth of 2D plates of Bi₂O₂Se on mica substrates can be realized. These vertically grown 2D nanoplates of Bi₂O₂Se can be conveniently transferred with their thermal properties investigated for the first time.     

High Oxide-Ion Conductivity through the Interstitial Oxygen Site in Sillén Oxychlorides

Oxide-ion conductors are gaining attention as future materials in energy applications, such as solid oxide fuel cells. Many Bi-containing compounds exhibit high oxide-ion conductivity via conventional vacancy mechanism. However, interstitial oxide-ion conduction is rare in Bi-containing materials. Herein, high oxide-ion conductivity is reported through interstitial oxygen sites in Sillén oxychlorides, LaBi_2−xTe_xO_4+x/2Cl (Bi₂LaO₄Cl-based oxychlorides). Oxide-ion conductivity of LaBi_1.9Te_0.1O_4.05Cl is 20 mS cm⁻¹ at 702 °C, and higher than best oxide-ion conductors as Bi₂V_0.9Cu_0.1O_5.35 below 201 °C. Despite of the presence of Bi and Te species, LaBi_1.9Te_0.1O_4.05Cl shows extremely high chemical and electrical stability at 400 °C from oxygen partial pressure 10⁻²⁵ to 0.2 atm and high chemical stability under CO₂ flow, wet 5% H₂ in N₂ flow, and air with natural humidity. Neutron scattering length density analysis, DFT calculations, and ab initio molecular dynamics simulations indicate that the extremely high oxide-ion conduction is attributed to cooperative diffusion through interstitial oxygen sites (interstitialcy diffusion mechanism) in triple fluorite-like layers. The present findings demonstrate the ability of LaBi_2−xTe_xO_4+x/2Cl as superior oxide-ion conductors, which can open new horizons for oxide-ion conductors.     

Oxygen‐Deficient Bismuth Oxide/Graphene of Ultrahigh Capacitance as Advanced Flexible Anode for Asymmetric Supercapacitors

Oxygen‐deficient bismuth oxide (r‐Bi₂O₃)/graphene (GN) is designed, fabricated, and demonstrated via a facile solvothermal and subsequent solution reduction method. The ultrafine network bacterial cellulose (BC) as substrate for r‐Bi₂O₃/GN exhibits high flexibility, remarkable tensile strength (55.1 MPa), and large mass loading of 9.8 mg cm^?2. The flexible r‐Bi₂O₃/GN/BC anode delivers appreciable areal capacitance (6675 mF cm^?2 at 1 mA cm^?2) coupled with good rate capability (3750 mF cm^?2 at 50 mA cm^?2). In addition, oxygen vacancies have great influence on the capacitive performance of Bi₂O₃, delivering significantly improved capacitive values than the untreated Bi₂O₃ flexible electrode, and ultrahigh gravimetric capacitance of 1137 F g^?1 (based on the mass of r‐Bi₂O₃) can be obtained, achieving 83% of the theoretical value (1370 F g^?1). Flexible asymmetric supercapacitor is fabricated with r‐Bi₂O₃/GN/BC and Co₃O₄/GN/BC paper as the negative and positive electrodes, respectively. The operation voltage is expanded to 1.6 V, revealing a maximum areal energy density of 0.449 mWh cm^?2 (7.74 mWh cm^?3) and an areal power density of 40 mW cm^?2 (690 mW cm^?3). Therefore, this flexible anode with excellent electrochemical performance and high mechanical properties shows great potential in the field of flexible energy storage devices.