Deposition Of Bi Research Articles

Enhanced photocatalysis-Fenton degradation of levofloxacin by Fe doped BiOCl microspheres with rich surface oxygen vacancies: The accelerated redox cycle of ≡Fe(III)/≡Fe(II)

The photocatalysis-Fenton process was considered as an effective water treatment method due to its superior efficiency and technical feasibility, but its application was limited by ≡Fe(III)/≡Fe(II). Herein, Fe doped BiOCl hierarchical microspheres with rich surface oxygen vacancies (Fe/BiOCl OVs) were synthesized to modulate the interface structure for efficient photocatalysis-Fenton degradation of levofloxacin (LEV). The systematic characterization analysis confirmed the existence of strong interfacial interactions, which facilitated the activation of H2O2 and the degradation of LEV. The synergism of metal deposition, OVs and surface plasmon resonance (SPR) effect of Bi contributed to the enhanced light absorption ability and suppressed carriers recombination. The LEV degradation efficiency reached 99.0% after 60-min photocatalysis-Fenton reaction. The interfacial charge transfer theory demonstrated that the presence of oxygen vacancies accelerated the redox cycle of ≡Fe(III)/≡Fe(II), which promoted the H2O2 activation to produce ·OH. The ·OH and e- played important roles during the photocatalysis-Fenton degradation of LEV, while ·O2–, 1O2 and h+ also contributed in LEV degradation. Based on density-functional theory (DFT) calculations and LC-MS analysis, four degradation pathways of LEV were proposed. The photocatalysis-Fenton degradation process of Fe/BiOCl OVs effectively reduced the toxicity of LEV, which ultimately mitigated the harmful effects of antibiotics on the environment.

Enhanced detection of trace sulfur levels in gasoline by bismuth electrode using square wave voltammetry

This study introduces a simple, cost-effective, and rapid bismuth electrode-square-wave voltammetry method for determining the total sulfur content in automotive gasoline. Optimal conditions for the developed electrode, including various Bi ion concentrations, deposition times, and potentials, were established on a glassy carbon electrode. The results demonstrated that the highest response was achieved when the bismuth electrode was placed in an acetate buffer and a methanol:toluene (1:1 v/v) solvent. The method was validated with and without a 30-second electro-preconcentration step. The voltammetric method in conjunction with the preconcentration step exhibited a sensitivity of 571.81 nA mg L−1, a limit of detection (LOD) of 0.02 mg L−1, and a limit of quantification (LOQ) of 0.08 mg L−1. Without the preconcentration step, the method yielded a sensitivity of 421.89 nA mg L−1, an LOD of 0.03 mg L−1, and an LOQ of 0.11 mg L−1. The developed method was applied to quantify commercial fuel samples. The results showed that the electrochemical technique yielded a similar total sulfur content to that measured by the standard ASTM D2622 method, with an error of less than 7.5%. Moreover, the method proposed in this study had lower LOD and LOQ limits, meeting the EURO5 and EURO6 regulations.

Growth mechanism of bismuth-filled nanoporous silicon with improved structural stability and low thermal conductivity

Nano porous silicon (PS) is a strong candidate for thermoelectric application, but it shows low structural stability and is prone to collapse. To enhance the structural stability of PS and offer a new way to improve its electrical conductivity, PS was prepared by electrochemical etching and Bi nanowires were fabricated in the pores of PS by electrodeposition. In addition, for studying the effect of structures on the properties of Bi-filled PS composites, aperiodic single-layer (SL) structure, and periodic rugate (Rgt) structure and Bragg structure PS samples were prepared by changing the etching current waveform and etching time. The results show that the initial Bi deposition position and filling fraction of Bi nanowires in PS templates can be precisely controlled. Since Bi nanowires have significantly different continuity in Rgt and Bragg structures compared with SL structures, we proposed two growth mechanisms of Bi nanowires, including the axis-growth mechanism and transverse-axis-growth mechanism, with the supports of the experimental results of XRD, SEM, and EDS.The room temperature thermal conductivities of pristine and Bi-filled PS layers are in the ranges of 4.5 ∼ 5.0 and 4.2 ∼ 6.0 W･m−1K−1, respectively, about 1/10 of the original unetched silicon wafer. No apparent increase of thermal conductivity was observed in any Bi-filled composites. In addition, the thermal conductivities of PS layers with Bragg structure, including pristine and Bi-filled PS composites, are significantly lower than those of the other two structures.SEM images also demonstrates that Bi greatly improved the mechanical property of PS composites, especially the periodic structures composites. This study firmly demonstrates that Bi-filling in PS with periodic Bragg structure is practical to obtain nanocomposites with low thermal conductivity and improved structural stability. It offers a new dimension to optimize the property of PS for thermoelectric application by pore configuration design and controllable nanowire Bi filling.

Revealing electrochemical behavior for high-quality and efficient bismuth deposition

Methanesulfonic acid (MSA, CH3SO3H) emerges as a sustainable and stable medium for membrane-assisted electrodeposition in bismuth (Bi) recovery. The incorporation of calcium lignosulfonate (CL) within the MSA-based system markedly improves the electrodeposition quality and efficiency of Bi, although the exact electrochemical mechanism and kinetics of CL's influence remains unclear and warrant further investigation. Our study focuses on the impact of CL on the electrochemical behavior through quantum chemical calculations, molecular dynamics simulations, electrochemical analyses and in-situ electrochemical optical microscopy. Within the primary solvation shell, Bi3+ associates closely with water and CH3SO3− ions, while CL is embedded in the secondary shell, forming a complex interaction network with Bi3+, H2O, and CH3SO3−, culminating in a solvation complex of Bi(CH3SO3)1.68·0.02CL·6·72H2O. This complex disrupts intra-solution hydrogen bonding, reduces water activity and undesirable side reactions, and thus promotes the electrodeposition efficiency. At the cathode's double electric layer, de-solvated Bi(CH3SO3)2+·nH2O ions are preferentially discharged and reduced. The pronounced physical adsorption of CL at the interface facilitates a three-dimensional electro-crystallization nucleation and growth process, yielding a uniform, smooth, and compact Bi deposit. Our findings not only extend the electrochemical understanding but also provide practical insights for optimizing Bi recovery in the CL-MSA system, with implications for the electrochemical recovery of other metals like lead and tin.

Emergence of quasi-1D spin-polarized states in ultrathin Bi films on InAs(111)A for spintronics applications.

The discovery, characterization, and control of heavy-fermion low-dimensional materials are central to nanoscience since quantum phenomena acquire an exotic and highly tunable character. In this work, through a variety of comprehensive experimental and theoretical techniques, it was observed and predicted that the synthesis of ultrathin Bi films on the InAs(111)A surface produces quasi-one-dimensional spin-polarized states, providing a platform for the realization of a unique spin-transport regime in the system. Scanning tunneling microscopy and low-energy electron diffraction measurements revealed that the InAs(111)A substrate facilitates the formation of the Bi-dimer phase of 2√3 × 3 periodicity with an admixture of the Bi-bilayer phase under submonolayer Bi deposition. X-ray photoelectron spectroscopy (XPS) measurements have shown the chemical stability of the Bi-induced phases, while spin and angle resolved photoemission spectroscopy (SARPES) observations combined with state-of-the-art DFT calculations have revealed that the electronic spectrum of the Bi-dimer phase holds a quasi-1D hole-like spin-split state at the Fermi level with advanced spin texture, whereas the Bi-bilayer phase demonstrates metallic states with large Rashba spin-splitting. The band structure of the Bi/InAs(111)A interface is discovered to hold great potential as a high-performance spintronics material fabricated in the ultimate two-dimensional limit.

The Influence of Deposit Interest Rates, BI 7 Day Reverse Repo Rate and Inflation on the Composite Stock Price Index in BEI during the 2020 - 2022 Pandemic

The aim of this research is to determine and understand the potential relationship between inflation, BI 7-day reverse repo rate, and deposit interest rates on the JCI movement in 2020 to 2022. The research approach used is a quantitative descriptive variation. This method uses three years of observational secondary data, to be precise from 2020 to 2022. Using Eviews 12 software, statistical tests and multiple regression analysis techniques are used in the data analysis process. The findings of this study show that the BI 7-day reverse repo rate and deposit interest rates both have quite a large and beneficial influence on the JCI movement. These results provide important information regarding stock market dynamics and economic variables that influence fluctuations in the IHSG value during the specified research period.

Atom-sharing Bi/Bi3O4Br plasmonic heterojunctions with effectively boosted photoelectrochemical activity for specific detection of chlorpyrifos

The increased environmental pollution caused by the overuse of the organophosphorus pesticide chlorpyrifos (CPF) has necessitated the development of an effective and selective photoelectrochemical (PEC) sensor. Herein, a Bi atom co-sharing Bi/Bi3O4Br plasmonic heterojunction was synthesized using an in-situ reduction process as a photoelectrode material to develop a highly selective PEC sensor for detecting CPF. Experimental characterizations and theoretical calculations demonstrate that the Bi atom-sharing heterostructure achieves tight contact in the heterointerface and effectively facilitates interfacial charge separation and migration. In addition, the deposition of Bi could greatly increase light-harvesting capacity of semiconductor materials resulting from the surface plasmon resonance (SPR) effect. Moreover, after the addition of CPF, the chelation between Bi3+ and C=N and P=S bonds in CPF hinders the mobility of photogenerated charges, leading to a decrease in the photocurrent signal intensity and selective determination of CPF. Compared to pristine Bi3O4Br, the proposed Bi/Bi3O4Br plasmonic heterojunction exhibits superior PEC activity. The developed PEC sensor showed a wide linear range (0.01–2000 ng/mL), a low detection limit of 0.0017 ng/mL (S/N=3), and superior selectivity and stability (RSD = 6.68%), which can be applied to CPF detection in tap water samples with recoveries of 97.2. to 102.9%. This study contributes to the rational design of a low-cost, highly efficient, and stable Bi-based plasmonic heterojunction for the CPF detection.

Electrochemical Investigations of Ag and Bi in Choline Chloride-Ethylene Glycol DES Electrolyte

Electrodeposition for silver and bismuth is currently carried out in alkaline solutions, e.g., by use of cyanide, and by electroplating these metals, by themselves or together. The electroplated products have important uses, e.g., in semiconductors [1].Choline Chloride (ChCl)-Ethylene Glycol (EG) DES mixtures, often referred to as ethaline, have been shown to have superior electrochemical properties compared to many other DES systems [2]. This system is considered a green solvent [3]. In this work, the electrochemical behaviour of Ag and Bi in ethaline electrolyte has been investigated to obtain the necessary parameters to extract them by electrochemical methods, either separately or together, when both are present in the DES electrolyte. The presence of Cu and Sb in the electrolyte, has also been studied, and its effect in the metal obtained has been evaluated. Ethaline solutions were fabricated by mixing together ChCl and EG at 1:2 ChCl:EG molar ratio by stirring at 60 °C until a clear liquid was formed. Model electrolyte solutions were then produced by dissolving AgCl and BiCl3, as well as SbCl3 and CuCl2, in the DES. Electrochemical investigations were carried out at 60 °C by cyclic voltammetry (CV), chronoamperometry (CA) and potentiostatic electrolysis using a 3-electrode setup.The CVs obtained using Pt-wire or GC-rod as working electrodes in the DES with 10 mM Ag(I) and Bi(III), showed two distinguished peaks in the cathodic scan. The CV and CA results showed that the Bi deposition starts at approximately 0.15-0.20 V more cathodic than the Ag deposition. Two or more electrochemical signals were observed in the reverse anodic scan, correlating to the dissolution of the metals, alloys and possible electrolyte reactions. Example of CV curve obtained on a Pt wire at a scan rate of 200 mV/s is included.The results indicated that it could be possible to electrochemically extract only Ag or both Ag and Bi simultaneously, when present at identical concentrations in the DES electrolyte, by carefully choosing the deposition potential. This was confirmed after analysis of the cathodic deposits on Pt and stainless steel (316L) substrates by Scanning Electron Microscopy-Energy Dispersive Spectroscopy (SEM-EDS).Experiments with Sb(III) and Cu(II), in addition to Ag(I) and Bi(III) present in the DES electrolyte showed that the cathodic deposition of the different metals appears in the order Ag<Sb<Bi<Cu. Significant co-deposition might occur, enhanced by favourable alloy formation, when metallic elements may deposit at activities lower than 1. Still, at 10 mM of each of the four metal salts present in the DES electrolyte, it was possible to obtain deposits with one, two, three or four metals present, by choosing the proper cathodic deposition potential.AcknowledgementsThis project has received funding from the EU’s Horizon 2020 research and innovation program under Grant Agreement 815748. The content in this presentation reflects only the views of the authors. The European Commission is not responsible for any use that may be made of the information it contains.

Comparative Study of the Underpotential Deposition of Bi in an Aqueous Electrolyte and an Ionic Liquid

Comparative Study of the Underpotential Deposition of Bi in an Aqueous Electrolyte and an Ionic Liquid

The Influence of Fiscal Policy and Monetary Policy on Economic Growth in Indonesia

The purpose of this study is to investigate how changes in fiscal policy and monetary policy have impacted economic expansion in Indonesia. Spending by the government, tax rates, the rate at which banks open new accounts, and the total amount of money in circulation are the variables that were investigated in this study. This study takes a quantitative approach, and the analytical method that is employed is multiple linear regression using secondary data on economic growth from 2013-2022. The data for this study was collected from the United States Department of Commerce. The study's conclusions indicate that taxes and the amount of money in circulation impact Indonesia's economic growth, but neither government spending nor interest rates on BI deposits do. Additionally, how government expenditure, taxes, interest rates, and the amount of money in circulation affect economic growth. It is 99.66%. As a result, while making future decisions about the economy, the government will need to take into account both kinds of policies in a comprehensive manner.

In-situ deposition of metal Bi on BiOBr/CdS S‐scheme heterojunction for effective photocatalytic H2O2 evolution via a two channel pathway

Photocatalytic H2O2 evolution from H2O and O2 has drawn growing attention, however, most current photocatalytic systems require the addition of sacrificial reagents to elevate the production activity. In this work, an efficient Bi/BiOBr-CdS S-scheme heterojunction was succeed synthesis via solvothermal method and exhibits a high H2O2 production activity of 346.4 μmol·L−1·h−1 via H2O oxidation accompanying with O2 reduction reactions. It is indicated that in synergistic effect of S-scheme heterojunction and metal Bi can reduce band gap, facilitate separation of charge carriers and induce high formation rate constants of H2O2. These works provide new strategies and ideas for the design of a S-scheme heterojunction to maximize redox ability.

Controllable Deposition of Bi onto Pd for Selective Hydrogenation of Acetylene.

The rational regulation of catalyst active sites at atomic scale is a key approach to unveil the relationship between structure and catalytic performance. Herein, we reported a strategy for the controllable deposition of Bi on Pd nanocubes (Pd NCs) in the priority order from corners to edges and then to facets (Pd NCs@Bi). The spherical aberration-corrected scanning transmission electron microscopy (ac-STEM) results indicated that Bi2O3 with an amorphous structure covers the specific sites of Pd NCs. When only the corners and edges of the Pd NCs were covered, the supported Pd NCs@Bi catalyst exhibited an optimal trade-off between high conversion and selectivity in the hydrogenation of acetylene to ethylene under ethylene-rich conditions (99.7% C2H2 conversion and 94.3% C2H4 selectivity at 170 °C) with remarkable long-term stability. According to the H2-TPR and C2H4-TPD measurements, the moderate hydrogen dissociation and the weak ethylene adsorption are responsible for this excellent catalytic performance. Following these results, the selectively Bi-deposited Pd nanoparticle catalysts showed incredible acetylene hydrogenation performance, which provides a feasible perspective to design and develop highly selective hydrogenation catalysts for industrial applications.

A 2D Bismuth-Induced Honeycomb Surface Structure on GaAs(111).

Two-dimensional (2D) topological insulators have fascinating physical properties which are promising for applications within spintronics. In order to realize spintronic devices working at room temperature, materials with a large nontrivial gap are needed. Bismuthene, a 2D layer of Bi atoms in a honeycomb structure, has recently attracted strong attention because of its record-large nontrivial gap, which is due to the strong spin-orbit coupling of Bi and the unusually strong interaction of the Bi atoms with the surface atoms of the substrate underneath. It would be a significant step forward to be able to form 2D materials with properties such as bismuthene on semiconductors such as GaAs, which has a band gap size relevant for electronics and a direct band gap for optical applications. Here, we present the successful formation of a 2D Bi honeycomb structure on GaAs, which fulfills these conditions. Bi atoms have been incorporated into a clean GaAs(111) surface, with As termination, based on Bi deposition under optimized growth conditions. Low-temperature scanning tunneling microscopy and spectroscopy (LT-STM/S) demonstrates a well-ordered large-scale honeycomb structure, consisting of Bi atoms in a √3 × √3 30° reconstruction on GaAs(111). X-ray photoelectron spectroscopy shows that the Bi atoms of the honeycomb structure only bond to the underlying As atoms. This is supported by calculations based on density functional theory that confirm the honeycomb structure with a large Bi-As binding energy and predict Bi-induced electronic bands within the GaAs band gap that open up a gap of nontrivial topological nature. STS results support the existence of Bi-induced states within the GaAs band gap. The GaAs:Bi honeycomb layer found here has a similar structure as previously published bismuthene on SiC or on Ag, though with a significantly larger lattice constant and only weak Bi-Bi bonding. It can therefore be considered as an extreme case of bismuthene, which is fundamentally interesting. Furthermore, it has the same exciting electronic properties, opening a large nontrivial gap, which is the requirement for room-temperature spintronic applications, and it is directly integrated in GaAs, a direct band gap semiconductor with a large range of (opto)electronic devices.

Maneuvering the Peroxidase-Like Activity of Palladium-Based Nanozymes by Alloying with Oxophilic Bismuth for Biosensing.

Engineering the catalytic performance of nanozymes is of vital importance for their broad applications in biological analysis, cancer treatment, and environmental management. Herein, a strategy to boost the peroxidase-like activity of Pd-based nanozymes with oxophilic metallic bismuth (Bi) is demonstrated, which is based on the incorporation of oxophilic Bi in the Pd-based alloy nanocrystals (NCs). To synthesize PdBi alloy NCs, a seed-mediated method is employed with the assistance of underpotential deposition (UPD) of Bi on Pd. The strong interaction of Bi atoms with Pd surfaces favors the formation of alloy structures with controllable shapes and excellent monodispersity. More importantly, the PdBi NCs show excellent peroxidase-like activities compared with pristine Pd NCs. The structure-function correlations for the PdBi nanozymes are elucidated, and an indirect colorimetric method based on cascade reactions to determine alkaline phosphatase (ALP) is established. This method has good linear range, low detection limit, excellent selectivity, and anti-interference. Collectively, this work not only provides new insights for the design of high-efficiency nanozymes, expands the colorimetric sensing platform based on enzyme cascade reactions, but also represents a new example for UPD-directed synthesis of alloy NCs.

Electronic structure of Bi nanolines on InAs(100)

Self-assembled nanolines are attractive to build the technological devices of next generation, but characterizing their electronic properties is often difficult to achieve. In this work we employ angle-resolved photoemission spectroscopy and density functional theory to clarify the electronic structure exhibited by self-assembled Bi nanolines grown on the InAs(100) surface. A surface resonance associated to the reconstructed ζ(4 × 2) surface is visible in the photoemission spectra before and after the formation of the Bi nanolines. This demonstrates that Bi deposition does not necessarily drive a transition to an unreconstructed surface in the substrate, which is contrary to what was reported in previous studies. In addition, experiment and theory show the presence of a flat band located in the band gap of InAs, just above the valence band maximum. This flat band is associated to the Bi nanolines and possesses a strong orbital character, consistent with its unidimensional nature. These spectral features suggest that Bi nanolines on InAs(100) may have a strongly polarized conductivity, which makes them suitable to be exploited as nanowires in nanotechnology. The coexistence with an accumulation layer suggests an even farther functionalization.

Combinatorial aerosol deposition of bismuth–antimony thermoelectric coatings with tunable composition

Aerosol deposition (AD) is commonly employed as a material processing step to generate coatings on substrates. In AD, aerosolized powders are passed through a nozzle and impacted at supersonic speeds onto the substrate. Plastic deformation of particles upon impact yields coatings with near bulk density. One key, unexploited advantage of aerosol processing is the ability to homogeneously mix disparate materials in the gas phase without concern over chemical compatibility or separation. Here, by using a custom-made voice-coil hopper injection (VHI) system for tunable injection of elemental powders, we demonstrate that AD can be applied directly in materials synthesis, depositing elemental precursor powders into homogeneous, dense coatings at adjustable atomic ratios. We examine the potential of combinatorial AD within the context of binary bismuth–antimony thermoelectric coating synthesis, adjusting the bismuth–antimony atomic ratio from 0.88:0.12, 0.75:0.25, to 0.5:0.5 and demonstrating that strongly adhered bismuth–antimony coatings can be produced via AD. Post-annealing is shown to yield solid bismuth–antimony solutions with thermoelectric properties approaching coatings produced by AD of pre-made, bismuth–antimony powders. Experiments are supplemented by molecular dynamics simulations of Bi and Sb nanoparticle sequential deposition, which reveal that the coating consolidation proceeds by plastic deformation and fracture of particles upon deposition.

The Ways for Bi on Pt to Enhance Formic Acid Oxidation

This work presents a correlation between the behavior of formic acid oxidation (FAO) on various Bi-modified Pt(poly) disk electrodes and their morphologies observed on Bi-modified Pt(111) disk electrodes using electrochemical scanning tunneling microscopy (EC-STM) to understand the effects of Bi on Pt. To distinguish the FAO activities of Bi on Pt and plain Pt around Bi, additional Pt was intentionally deposited using two different routes: direct route and iodine route. In direct route, Pt was directly deposited on Bi islands and plain Pt sites around Bi islands, while in iodine route, Pt was exclusively deposited on Bi islands by protecting plain Pt sites with adsorbed iodine. Thus, a comparison of FAO performances on the two Bi-modified Pt electrodes with additional Pt (deposited in the different ways) disclosed a difference in FAO performances on plain Pt sites and Bi islands. When Bi coverage was ~0.04, the Bi deposits were scattered Bi islands enhancing FAO on Pt(poly). The additional Pt deposits using direct route increased FAO efficiency, while the ones using iodine route slightly decreased FAO current. The EC-STM observations indicated that Pt deposits around Bi islands, not on Bi islands, were responsible for the FAO current increase on Bi-modified Pt(poly). The FAO efficiency on Bi-modified Pt(poly) with a Bi coverage of ~0.25 increased by a factor of 2. However, the additional Pt deposits using the two Pt deposition routes notably decreased the FAO current. The dependency of FAO on Bi coverage was discussed in terms of electronic effect and ensemble effect.

Electrodeposition of bismuth at a graphene modified carbon electrode and its application as an easily regenerated sensor for the electrochemical determination of the antimicrobial drug metronidazole

Metronidazole is a well-known antimicrobial drug that belongs to the nitroimidazole family of antibiotics. It has been widely used in the treatment of infections, but its accumulation in aquatic environments is an emerging concern. In this study a glassy carbon electrode was modified with graphene (Gr) nanoplatelets and bismuth. Both the Gr and Bi were electrochemically deposited onto the glassy carbon and the modified electrode was employed in the electrochemical detection of metronidazole. At the modified electrode, the reduction of metronidazole was found to be an adsorption-controlled reaction. The optimised sensor, which was fabricated within 6 min, exhibited good selectivity in the presence of various inorganic and organic compounds, good recovery in tap water, and exhibited a linear calibration curve extending from 0.005 to 260 μM, with a limit of detection of 0.9 nM. The sensor was easily regenerated through the simple oxidation of the Bi deposit followed by a 100 s reduction period in the Bi(III) solution to give a newly generated surface. Good reproducibility was achieved using this simple regeneration approach.

An evolution to Bismuth dopant concentration on properties of CdSe films for solar cell appliances

The deliberated introduction of dopant to the crystalline host lattice is a promising approach towards the adjustment of physical properties. The present work deals with the influence of Bi dopant concentration on crystallographic, optical, topographical and electrical features of CdSe films for absorber layer applications to solar cells. Herein, the deposition of undoped and Bi doped CdSe films having 1%, 3% and 5% Bi dopant concentration is carried out via resistive heating thermal evaporation method. The crystallographic patterns reveal to the polycrystalline nature of films with occurrence of major reflection along (111) plane of cubic CdSe system where the intensity of this peak is substantially altered with Bi dopant. The crystallite size and strain of the CdSe films are appeared in range of 32–53 nm and 3.01 × 10−3–5.06 × 10−3, respectively upon changing the Bi doping. Optical study indicates the manifestation of strong absorption in visible region of spectra and fluctuation in absorbance of CdSe films with change in Bi dopant concentration. The optical band gap of undoped and Bi doped CdSe films is obtained in 1.61–1.69 eV range. Electrical assessment of films points towards creation of Ohmic contacts where the conductivity of films is improved at 1% Bi doping and decreased at higher doping. All the films show spherical shaped grains with variable density where the grain size obtained from AFM analysis is varied from 24 nm to 40 nm with Bi dopant concentration. Hence, the concentration of trivalent Bi dopant plays a pivotal role in modulation of properties of CdSe films for absorber layer appliances.

(Keynote) Pro and Con of Bi-Decorated Carbon Felts in Vanadium Redox Flow Batteries

Carbon felts are commonly utilized electrodes in vanadium flow batteries due to their low cost, light weight, good electronic conductivity, and chemical inertness. In contrast, their activity in catalyzing the vanadium redox reactions is less remarkable. In particular at the negative side, where V3+ reduction competes with the parasitic hydrogen evolution reaction (HER) at low potentials. In the literature, the addition of Bi3+ into the electrolyte [1] or its deposition on the felts has been suggested as a remedy. However, it is not clear yet, whether the Bi decoration remains stable with time and cycling and which mechanisms are responsible for the observed performance increase.The aim of this work is therefore to unravel more details about the catalyzing effect of Bi and its stability on the cell level. To this effect, the electrode kinetics with and without Bi decoration were studied comparing results obtained using Friedl’s method [2] with cyclic voltammetry (CV) data analyzed by the Polarographica curve fitting routine [3]. This approach can also be generalized to obtain precise kinetic information with other decorating metals.We furthermore applied negative dynamic hydrogen bubble templating (DHBT) deposition as an interesting way to coat commercially available carbon felts with a structured metallic layer of high surface area. Using this strategy, a significant positive effect was observed. However, the drying parameters and post-processing of the felts are important parameters which severely affect the final performance.In order to study the stability of Bi deposits in realistic battery experiments, in-situ synchrotron radiography has been used to monitor the Bi-decorated felts during charge-discharge cycles [4]. The figure demonstrates the effect of different flow rates on the Bi deposition patterns. Dark spots show metal-decorated areas within the felts at flow rates of 5 mlmin-1 (left), 15 mlmin-1 (middle) and 25 mlmin-1 (right). It can be easily seen that the operation conditions influence the felt decoration significantly, while Bi deposits dissolve and deposit during the charge-discharge routine. Further studies will be necessary to find out a) whether different deposit positions affect the performance enhancement and b) if DHBT-Bi remains more stable under operating conditions.In our presentation, we will not only focus on the materials, but also highlight techniques especially suitable for the stuctural and electrochemical analysis of felt electrodes.[1] B. Li, M. Gu, Z. Nie, Y. Shao, Q. Luo, X. Wei, X. Li, J. Xiao, C. Wang, V. Sprenkle, W. Wang, Bismuth Nanoparticle Decorating Graphite Felt as a High-Performance Electrode for an All-Vanadium Redox Flow Battery, Nano Letters 13(3) (2013) 1330-1335.[2] J. Friedl and U. Stimming, Determining Electron Transfer Kinetics at Porous Electrodes, Electrochim. Acta 227 (2017) 235–245.[3] T. Tichter, J. Schneider, D. Andrae, M. Gebhard, and C. Roth, Universal algorithm for simulating and evaluating cyclic voltammetry atmacroporous electrodes by considering random arrays of microelectrodes, ChemPhysChem 21 (2019) 428 –441.[4] M. Gebhard, T. Tichter, J. Schneider, J. Mayer, A. Hilger, M. Osenberg, M. Rahn, I. Manke, C. Roth J. Power Sources 478 (2020) 228695. Figure 1