Effect of dimensional expansion on carrier transport behaviors of the hexagonal Bi-based perovskite crystals

All-inorganic Cs_(3)Bi_(2)I_(9)(CBI)halide perovskites are sought to be candidate for photoelectrical materials because of their low toxicity and satisfactory stability.Unfortunately,the discrete molecular[Bi2I9]3−clusters limit the charge-transport behaviors.Herein,the defect halide perovskite based on trivalent Bi^(3+)is expanded to Cs_(3)Bi_(2)I_(6)Br_(3)(CBIB).Centimeter-size CBIB single crystal(Φ15×70 mm^(3))was grown by the vertical Bridgeman method.The powder X-ray diffraction analysis shows that CBIB has structure with lattice parameters of a=b=8.223Å,c=10.024Å,α=β=90°andγ=120°.The density functional theory(DFT)calculations demonstrate that the charge density distribution was enhanced after the dimensional expansion.The enhancement of carrier transport ability of(00l)in-plane is characterized before and after dimensional improvement.The obtained CBIB(001)exhibited an electron mobility up to 40.03 cm^(2)V^(−1)s^(−1)by time-of-flight(TOF)technique,higher than 26.46 cm^(2)V^(−1)s^(−1)of CBI(001).Furthermore,the X-ray sensitivity increases from 707.81μC Gy^(−1)cm^(−2)for CBI(001)to 3194.59μC Gy−1 cm^(−2)for CBIB(001).This research will deepen our understanding of Bi-based perovskite materials and afford more promising strategies for lead-free perovskite optoelectronic devices modification.

THE PRINCIPAL CONSTRUCTIVE PROCESS OF UNIT CELL IN Bi-BASED SUPERCONDUCTORS

In this paper, 2201 and 2212 phases as the corresponding precursor of forming 2212 and 2223 phases are discussed,and the constructive process of unit cell of 2201 phase is ascertained by XRD and chemical kinetics method. Subsequently, the process of 221

Selenium Doping in Bi-based Superconductors

Six different compositions in Bi2Sr2Ca2Cu3Oy:Sex with x=0.0, 0.05, 0.1, 0.2, 0.3, 0.4 have been prepared by the solid state reaction method to explore doping of selenium in the system. Sintering at 847±4℃ and subsequent annealing at 827℃ has been carried out for different time periods. The samples have been characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), and measurement of resistance below room temperature has been carried out by four-probe method. Superconducting transition temperature (Tc) value shows dependence on Se concentration: the highest Tc(0)=:94 K is observed for x=0.3. A detailed Auger electron spectroscopic (AES) analysis has been carried out to investigate the presence of Se in the grains of the superconductors. It has also been found that Se increases the Tc(0) value and promotes the formation of high temperature superconducting phase (2223), which coexists with low temperature phase (2212) in the sintered samples.

Charge Transfer and Normal State Anomaly in Bi-Based High T_c Superconductors Studied by Positron Annihilation

The positron annihilation lifetime and Doppler broadened line-shapeparameter have been measured between 77 and 300 K for Bi1.8Pb0.1Sb0.1Sr2Ca2Cu3Ox,Bi1.8Sb0.2Sr2Ca2Cu3Ox and Bi1.7Pb0.2Sb0.1Sr2Ca2Cu2Ox. The charge transfer from Cu-Olayers to Bi-O layers has been observed across Tcs for all samples.Three samples allshow two normal state anomalies around 160 K and 240 K,respectively.The anomalyaround 160 K is attributed to the structural instability and that around 240 Kpresumably to the displacement phase transition.

Electrocatalytic CO_(2) Reduction over Bimetallic Bi-Based Catalysts:A Review

Electrocatalytic reduction of carbon dioxide(CO_(2))to valuable fuels is an up-and-coming approach.Owing to the low cost,environmental friendliness,and high selectivity to formate single product at low overpotentials,bismuth(Bi)-based catalysts have attracted extensive research attention.In this review,the reaction mechanisms of Bi-based catalysts are first introduced,and the bimetallic Bi-based catalysts synthesized by alloying,doping,and loading strategies are reviewed from the aspects of catalyst component,morphology,synthesis procedure,and performance optimization for electrocatalytic CO_(2)reduction.We provide an in-depth discussion of the existing challenges and an outlook for this highly promising kind of electrocatalysis.

THE STRUCTURAL PHASE TRANSITION NEAR 210 K OF Bi-BASED SUPERCONDUCTORS

Recently, systematic investigations on Bi-based superconductors were carried out by means of ultrasonic measurements, thermal analysis, specific heat experiments and X-ray diffraction measurements. It was found for the first time that a possible structural phase transition occurs near 210 K in these systems. All the samples used were of single phase

Bi-BASED HIGH T_c SUPERCONDUCTING LOOP ANTENNA

INTRODUCTIONIn order to improve the efficiency of the electrically small antenna, which has the physical extension smaller than the maximum free space wavelength transmitted or received, superconducting materials began to be utilized in fabricating antennas since 1960s. In 1988, the Birmingham group of UK made for the first time the small dipole antennas

Optical Spectroscopy of Er^(3+) and Er^(3+)/Yb^(3+)Co-doped Bi_2O_3-GeO_2-B_2O_3-ZnO Glasses

The （60 - x）Bi2O3 - xGeO2-30B2O3-10ZnO （x = 5, 10, 20, 30 molar percent） glasses doped with Er^3＋ and Er^3＋/Yb^3＋ were fabricated using the melting method. The thermal stability of the glasses was studied with their DTA curves. The results show that the difference between the glass transition temperature and the crystallization onset temperature increases with the increase of GeO2 content, indicating that the thermal stability of the glass has become better. The absorption spectra were recorded and the stimulated emission cross sections were calculated using the McCumber theory. The Ω2, O4, and Ω6 parameters,the transition probability, the radiative lifetime, and the fluorescence branch ratio of Er^3＋ for optical transition were calculated from their absorption spectra in terms of reduced matrix U^（t）（λ = 2, 4, 6） character for optical transitions. The infrared emission of Er^3＋ was measured upon excitation with 970 nm light and the full width at half-maximum （FWHM） was estimated from the emission spectra. The pumping efficiency and the intensity of the emission at the 1.54 μm band of Er^3＋ were enhanced considerably by co-doping Yb^3＋ .

Rational design of bismuth-based catalysts for electrochemical CO_(2) reduction

Sustainable conversion of carbon dioxide(CO_(2))to high value-added chemicals and fuels is a promising solution to solve the problem of excessive CO_(2) emissions and alleviate the shortage of fossil fuels,maintaining the balance of the carbon cycle in nature.The development of catalytic system is of great significance to improve the efficiency and selectivity for electrochemical CO_(2) conversion.In particular,bismuth(Bi)based catalysts are the most promising candidates,while confronting challenges.This review aims to elucidate the fundamental issues of efficient and stable Bi-based catalysts,constructing a bridge between the category,synthesis approach and electrochemical performance.In this review,the categories of Bi-based catalysts are firstly introduced,such as metals,alloys,single atoms,compounds and composites.Followed by the statement of the reliable and versatile synthetic approaches,the representative optimization strategies,such as morphology manipulation,defect engineering,component and heterostructure regulation,have been highlighted in the discussion,paving in-depth insight upon the design principles,reaction activity,selectivity and stability.Afterward,in situ characterization techniques will be discussed to illustrate the mechanisms of electrochemical CO_(2) conversion.In the end,the challenges and perspectives are also provided,promoting a systematic understanding in terms of the bottleneck and opportunities in the field of electrochemical CO_(2) conversion.

Optical Spectroscopy of Er^(3+), Er^(3+)/Yb^(3+) Co-doped Bi_2O_3-GeO_2-B_2O_3-ZnO Glasses

The （60 - x） Bi2O3-xGeO2-30B2O3-10ZnO （x = 5, 10, 20, 30 molar percent） glasses doped with Er^3＋ and Er^3＋/Yb^3＋ were fabricated by melting method. The thermal stability of the glasses was studied by their DTA curves. The results indicate that the difference between the glass transition temperature and the crystallization onset temperature increase as increase of GeO2 content, indicating that the thermal stability of the glass becomes better. The absorption spectra were recorded. The stimulated emission cross sections were calculated by McCumber theory. The Ω2, Ω4, and Ω6 parameters, transition probability, radiative lifetime, fluorescence branch ratio of Er^3＋ for optical transition were calculated from their absorption spectra in terms of reduced matrix U^（1）（λ = 2, 4, 6） character for optical transitions. The infrared emission was measured by excitation with 970 nm light and the FWHM was estimated from their emission spectra. The pumping efficiency and the intensity of emission at the band of 1.54 μm are enhanced greatly by addition of Y2O3.

On the Isotope-Like Effect for High-T_cSuperconductors in the Scenario of 2-Phonon Exchange Mechanism for Pairing

By generalizing the isotope effect for elemental superconductors (SCs) to the case of pairing in the 2-phonon exchange mechanism for composite SCs, we give here an explanation of the well-known increase in the critical temperature (Tc) of Bi2Sr2CaCu2O8 from 95 K to 110 K and of Bi2Sr2Ca2Cu3O10 from 105 to 115 - 125 K when Bi and Sr in these are replaced by Tl and Ba, respectively. On this basis, we also give the estimated Tcs of some hypothetical SCs, assuming that they may be fabricated by substitutions similar to Bi → Tl and Sr → Ba.

Surface iodine and pyrenyl-graphdiyne co-modified Bi catalysts for highly efficient CO_(2) electroreduction in acidic electrolyte

CO_(2) electroreduction to formic acid/formate would contribute to alleviating the energy and climate crisis.This work reports a Bi-based catalyst derived from the in-situ electroreduction of Bi_(2)O_(2)CO_(3) modified with iodine and pyrenyl-graphdiyne(PGDY)on the surface for efficient electroreduction of CO_(2) in acidic electrolyte,with a high partial current density of 98.71 mA·cm^(-2) and high Faradaic efficiency(FE)>90%over the potential range from^(-1).2 to-1.5 V vs.reversible hydrogen electrode(RHE),as well as the long-term operational stability over 240 h without degradation in H-type cell.Experimental results and density function theory calculations show that the synergistic effect of surface iodine and PGDY is responsible for this active and extremely stable process of CO_(2) electroreduction via lowering the energy barriers for formation of*OCHO intermediate,suppressing the competitive HER by enhancing the concentration of both K+and CO_(2) at reaction interface,as well as preventing the dissolution and re-deposition of active Bi atoms on surface during catalytic reaction.This work provides new insight into designing highly active and stable electrocatalysts for CO_(2) reduction.

X-ray Photoelectron Spectra of Fluorine-doped 2223 Phase Bi-base Superconductor

Since the discovery of Bi-base superconductors, investigations on their bonding and electronic configuration have been reported. Koniki et al. discussed the distribution and properties of Bi, Sr and Ca in crystal; Kihida et al. pointed out that the binding energy E of Cu 2p3/2 is unchanged in the Bi-Sr-Cu-O,（Bi,Pb）Sr-Cu-O,

Emerging Bismuth-Based Step-Scheme Heterojunction Photocatalysts for Energy and Environmental Applications

Photocatalysis has been expected to be a promising advanced oxidation process to endlessly convert exhaustless solar energy into storable,transportable,and usable chemical energy.As a kind of visible light-response semiconductors,Bi-based semiconductors can be developed into step-scheme(S-scheme)heterojunction photocatalysts,consisting of a reductive photocatalyst(RP)and an oxidative photocatalyst(OP)with band edge bending.This review sums up the state-of-the-art progress in Bi-based S-scheme heterojunctions,as well as the in-/ex-situ experiments and theoretical calculations to uncover the unique heterostructure and charge transfer mechanism of Bi-based S-scheme heterojunctions in depth.We can find that Bi-based S-scheme heterojunction photocatalysts have advantages in impeding the recombination of photo-induced electron-hole pairs,expediting the charge transfer,broadening solar energy utilization,and maximizing the potential energy of photo-redox reaction sites.Additionally,the recently published work on the potential applications of Bi-based S-scheme heterojunctions is also summarized,including photocatalytic H_(2) production,CO_(2) reduction with water,pollutant degradation,H_(2)O_(2) production,and N_(2) photofixation for ammonia and urea production by comparing and discussing their photocatalytic efficiency.On the basis of research progress,the immediate challenges and future perspectives of Bi-based S-scheme heterojunction photocatalysts are critically debated.

Chloroplast-like porous bismuth-based core–shell structure for high energy efficiency CO2 electroreduction

Electrochemical CO2 reduction reaction(CO2RR)to formate is economically viable considering the energy input and market value.Through learning nature,a series of chloroplast-like porous bismuth-based core–shell(CPBC)materials have been designed.In these materials,the porous carbon can enrich and transfer CO2 to the core–shell Bi@Bi2O3 in CO2 reduction process,during which Bi2O3 layer can be transformed into activated metastable layer to efficiently convert CO2 into formate and Bi can provide abundant electrons.Based on this,superior performances for most of important parameters in CO2 RR can be achieved and best of them,CPBC-1 presents remarkable Faradaic efficiency(FEformate>94%)over a wide potential range(-0.65 to-1.0 V)with high catalysis durability(>72 h).Noteworthy,its maximum energy efficiency is as high as 76.7%at-0.7 V,the highest one in reported bismuth-based materials.This work opens novel perspectives in designing nature-inspired CO2RR electrocatalysts.

Recent advances in special morphologic photocatalysts for NO_(x)removal

The significant increase of NO_(x)concentration causes severe damages to environment and human health.Light-driven photocatalytic technique affords an ideal solution for the removal of NO_(x)at ambient conditions.To enhance the performance of NO_(x)removal,1D,2D and 3D photocatalysts have been constructed as the light absorption and the separation of charge carriers can be manipulated through controlling the morphology of the photocatalyst.Related works mainly focused on the construction and modification of special morphologic photocatalyst,including element doping,heterostructure constructing,crystal facet exposing,defect sites introducing and so on.Moreover,the excellent performance of the photocatalytic NO_(x)removal creates great awareness of the application,which has promising practical applications in NO_(x)removal by paint(removing NO_(x)indoor and outdoor)and pavement(degrading vehicle exhausts).For these considerations,recent advances in special morphologic photocatalysts for NO_(x)removal was summarized and commented in this review.The purpose is to provide insights into understanding the relationship between morphology and photocatalytic performance,meanwhile,to promote the application of photocatalytic technology in NO_(x)degradation.