Metal Halide Research Articles

Modulating the Electronic Structure of Metal Halide Perovskites for Efficient Selective CO2 Photoreduction to CO

Metal halide perovskites (MHPs) have recently held great promise for solar-to-fuel conversion via artificial photosynthesis technology. However, the conversion efficiency of most MHP photocatalysts is still far below that necessary for their practical implementation. Modulating the electronic structure is a promising strategy to solve this issue. Here, taking Cs2AgBiBr6 as a prototype, we investigate the interplay between the local electronic structure of Cs2AgBiBr6 and its photocatalytic performance via introducing heteroatoms. Theoretical calculations reveal that Au heteroatom-mediated orbital rehybridization induces high electron densities and tailors the d-band center of Cs2AgBiBr6, endowing more upshifted d-band center and enhanced adsorption strength of intermediates, thereby resulting in decreased energy barriers for selective CO2 photoreduction to CO product. Experimentally, we report the Cu-incorporated Cs2AgBiBr6 catalyst for selective photoreduction of CO2 to CO in a solid-gas system without sacrificial agents, yielding an on average CO generation rate of 47.3 μmol g−1 with approximately 100% selectively, outperforming the pure Cs2AgBiBr6 and comparable to the reported MHP-based photocatalysts. This work showcases modulating the electronic structure of MHP photocatalysts offering a powerful route for effective solar fuel generation.

Thiourea-Induced Cocrystallization of Mixed-Halide Perovskite Thin Films for High-Performance Pure Blue Perovskite Light Emitting Diodes

Metal halide perovskite light-emitting diodes (PeLEDs) are gaining significant attention towards next-generation display materials owing to their advantageous properties, including color tunability, exceptionally narrow bandwidth, and high luminescence. Recent studies have successfully achieved over 20% external quantum efficiencies (EQE) in green and red PeLEDs. However, the blue PeLEDs lag far behind those of green or red PeLEDs because unstable phase stability in mixed halide perovskite thin films under high turn-on voltage (Von). In specific, the blue emission usually possesses halide ions with smaller ionic radius (Cl- or Br-), which easily migrates under high operative bias generating significant halogen vacancies and phase-transformation. In this context, we suggest thiourea as a promising additive for stabilizing defective perovskite thin films. Thiourea is a well-known hydrogen bond donor to halogens, which allows potential coordination complex of thiourea-halide ions to encompass well-dispersed mixed halides in co-crystallized perovskite lattices. In addition, the strong coordination of the C=S···Pb2+ was also demonstrated the thiourea-incorporated perovskite films, which effectively passivated undercoordinated Pb2+ antisites. Consequently, the thiourea-incorporated perovskite films exhibited stable deep-blue emission within 460 nm, demonstrating excellent luminance and quantum efficiency in pure blue PeLEDs. Moreover, the addition of thiourea achieved decreased Von and excellent spectral stability of pure blue PeLEDs at high applied bias, leading to significant advancements in pure blue perovskite display technology.

Enhancing photovoltaic efficiency in perovskite solar cells through synergistic blending of polyvinyl alcohol and F-127 polymer in a sandwich architecture

In the field of photovoltaics, perovskite solar cells (PSCs) have become increasingly popular because of their cost-effective processing and competitive efficiency when compared to silicon solar cells. This work presents a novel design of a PSC based on methyl ammonium lead iodide (CH3NH3PbI3) and investigates the possibilities of organic-inorganic metal halides in the field of PSCs. The device has a sandwich architecture, where the hole transport material (HTM) operates at room temperature using a blend of polyvinyl alcohol (PVA) and F-127 polymer. Under typical solar conditions, the built-in PSC, which has the architecture FTO/TiO2/Perovskite/PVA & F-127/Pt, exhibits a remarkable efficiency of 1.29 %. Interestingly, PSC stability at room temperature is still a major problem, yet our design demonstrates a remarkable 2-h stability in ambient circumstances. This accomplishment is ground breaking because it introduces a high-efficiency PSC in a sandwich construction operating in ambient settings for the first time. The fact that this novel technique is solution-based and does not require vacuum deposition lends even more credence to its viability and scalability.

Single Crystal Ruddlesden-Popper and Dion-Jacobson Metal Halide Perovskites for Visible Light Photodetectors: Present Status and Future Perspectives.

2D metal halide perovskites (MHPs), mainly the studied Ruddlesden-Popper (RP) and Dion-Jacobson (DJ) phases, have gained enormous popularity as optoelectronic materials owing to their self-assembled multiple quantum well structures, tunable semiconducting properties, and improved structural stability compared to their bulk 3D counterparts. The performance of polycrystalline thin film devices is limited due to the formation of defects and trap states. However, as studied so far, single crystal-based devices can provide a better platform to improve device performance and investigate their fundamental properties more reliably. This Review provides the first comprehensive report on the emerging field of RP and DJ perovskite single crystals and their use in visible light photodetectors of varied device configurations. This Review structurally summarizes the 2D MHP single crystal growth methods and the parameters that control the crystal growth process. In addition, the characterization techniques used to investigate their crystal properties are discussed. The review further provides detailed insights into the working mechanisms as well as the operational performance of 2D MHP single crystal photodetector devices. In the end, to outline the present status and future directions, this Review provides a forward-looking perspective concerning the technical challenges and bottlenecks associated with the developing field of RP and DJ perovskite single crystals. Therefore, this timely review will provide a detailed overview of the fast-growing field of 2D MHP single crystal-based photodetectors as well as ignite new concepts for a wide range of applications including solar cells, photocatalysts, solar H2 production, neuromorphic bioelectronics, memory devices, etc.

The Crystal Structure, Band Gap, and Optoelectronic Performance of Lead‐free Cs2PdBr4 Metal halide Single Crystal and its Thin film

The Crystal Structure, Band Gap, and Optoelectronic Performance of Lead‐free Cs2PdBr4 Metal halide Single Crystal and its Thin film

Crown Ethers with Different Cavity Diameters Inhibit Ion Migration and Passivate Defects toward Efficient and Stable Lead Halide Perovskite Solar Cells.

Organic-inorganic hybrid metal halide perovskite solar cells have been considered as one of the most promising next-generation photovoltaic technologies. Nevertheless, perovskite defects and Li+ ionic migration will seriously affect the power conversion efficiency and stability of the formal device. Herein, we designed two crown ether derivatives (PC12 and PC15) with different cavity diameters, which selectively bind to different metal cations. It is found that PC15 in perovskite precursor solution can actively regulate the nucleation and crystallization processes and passivate the uncoordinated Pb2+ ions, while PC12 at the interface between the perovskite layer and hole-transporting layer can effectively inhibit the migration of Li+ ions and reduce nonradiative recombination losses. Therefore, PC12 and PC15 can act as "lubricant" and defect passivators, as well as inhibitors of ion migration, when they are synergistically applied at the surface and bulk of perovskite layer. Consequently, the optimized device achieved a champion efficiency of 24.8% with significantly improved humidity, thermal, and light stability.

Deep Blue CsPbBr3 Quantum Wires with Tailored Shapes.

Low-dimension metal halide perovskites are attractive for bandgap tunable optoelectronic materials. Among them, 1-D CsPbBr3 quantum wires (QWs) are emerging as promising deep-blue luminescent material. However, the growth dynamics of 1-D perovskite QWs are intricate, making the study and control of 1-D QWs highly challenging. In this study, a strategy for controlling both the length and width of the CsPbBr3 QWs was realized. The temperature-dependent isotropic growth mechanism was revealed and employed as the main tool for the oriented growth of 1-D CsPbBr3 QWs for various aspect ratios. Our results pave the way for the controlled synthesis of ultrasmall perovskite nanocrystals.

Surface Structure of Lecithin-Capped Cesium Lead Halide Perovskite Nanocrystals Using Solid-State and Dynamic Nuclear Polarization NMR Spectroscopy.

Inorganic colloidal cesium lead halide perovskite nanocrystals (NCs) encapsulated by surface capping ligands exhibit tremendous potential in optoelectronic applications, with their surface structure playing a pivotal role in enhancing their photophysical properties. Soy lecithin, a tightly binding zwitterionic surface-capping ligand, has recently facilitated the high-yield synthesis of stable ultraconcentrated and ultradilute colloids of CsPbX3 NCs, unlocking a myriad of potential device applications. However, the atomic-level understanding of the ligand-terminated surface structure remains uncertain. Herein, we use a versatile solid-state nuclear magnetic resonance (NMR) spectroscopic approach, in combination with dynamic nuclear polarization (DNP) and atomistic molecular dynamics (MD) simulations, to explore the effect of lecithin on the core-to-surface structures of CsPbX3 (X = Cl or Br) perovskites, sized from micron to nanoscale. Surface-selective (cross-polarization, CP) solid-state and DNP NMR (133Cs and 207Pb) methods were used to differentiate the unique surface and core chemical environments, while the head-groups {trimethylammonium [-N(CH3)3+] and phosphate (-PO4-)} of lecithin were assigned via 1H, 13C, and 31P NMR spectroscopy. A direct approach to determining the surface structure by capitalizing on the unique heteronuclear dipolar couplings between the lecithin ligand (1H and 31P) and the surface of the CsPbCl3 NCs (133Cs and 207Pb) is demonstrated. The 1H-133Cs heteronuclear correlation (HETCOR) DNP NMR indicates an abundance of Cs on the NC surface and an intimate proximity of the -N(CH3)3+ groups to the surface and subsurface 133Cs atoms, supported by 1H{133Cs} rotational-echo double-resonance (REDOR) NMR spectroscopy. Moreover, the 1H-31P{207Pb} CP REDOR dephasing curve provides average internuclear distance information that allows assessment of -PO4- groups binding to the subsurface Pb atoms. Atomistic MD simulations of ligand-capped CsPbCl3 surfaces aid in the interpretation of this information and suggest that ligand -N(CH3)3+ and -PO4- head-groups substitute Cs+ and Cl- ions, respectively, at the CsCl-terminated surface of the NCs. These detailed atomistic insights into surface structures can further guide the engineering of various relevant surface-capping zwitterionic ligands for diverse metal halide perovskite NCs.

Efficient Deep-Blue Light-Emitting Diodes Through Decoupling of Colloidal Perovskite Quantum Dots.

Metal halide perovskite light-emitting diodes (PeLEDs) have exceptional color purity but designs that emit deep-blue color with high efficiency have not been fully achieved and become more difficult in the thin film of confined perovskite colloidal quantum dots (PeQDs) due to particle interaction. Here it is demonstrated that electronic coupling and energy transfer in PeQDs induce redshift in the emission by PeQD film, and consequently hinder deep-blue emission. To achieve deep-blue emission by avoiding electronic coupling and energy transfer, a QD-in-organic solid solution is introduced to physically separate the QDs in the film. This physical separation of QDs reduces the interaction between them yielding a blueshift of ≈7nm in the emission spectrum. Moreover, using a hole-transporting organic molecule with a deep-lying highest occupied molecular orbital (≈6.0eV) as the organic matrix, the formation of exciplex emission is suppressed. As a result, an unprecedently high maximum external quantum efficiency of 6.2% at 462nm from QD-in-organic solid solution film in PeLEDs is achieved, which satisfies the deep-blue color coordinates of CIEy <0.06. This work suggests an important material strategy to deepen blue emission without reducing the particle size to <≈4nm.

Versatile Method for Preparing Two-Dimensional Metal Dihalides.

Ever since the ground-breaking isolation of graphene, numerous two-dimensional (2D) materials have emerged with 2D metal dihalides gaining significant attention due to their intriguing electrical and magnetic properties. In this study, we introduce an innovative approach via anhydrous solvent-induced recrystallization of bulk powders to obtain crystals of metal dihalides (MX2, with M = Cu, Ni, Co and X = Br, Cl, I), which can be exfoliated to 2D flakes. We demonstrate the effectiveness of our method using CuBr2 as an example, which forms large layered crystals. We investigate the structural properties of both the bulk and 2D CuBr2 using X-ray diffraction, along with Raman scattering and optical spectroscopy, revealing its quasi-1D chain structure, which translates to distinct emission and scattering characteristics. Furthermore, microultraviolet photoemission spectroscopy and electronic transport reveal the electronic properties of CuBr2 flakes, including their valence band structure. We extend our methodology to other metal halides and assess the stability of the metal halide flakes in controlled environments. We show that optical contrast can be used to characterize the flake thicknesses for these materials. Our findings demonstrate the versatility and potential applications of the proposed methodology for preparing and studying 2D metal halide flakes.

Evaluation of the design features and components for a large-scale solar simulator for PV module testing

The evaluation of photovoltaic devices must be carried out in laboratories under stable conditions of irradiance, spatial uniformity, and spectral mismatch. Large-scale solar simulators are a reliable option for this. Various designs of simulators have been reported; however, more needs to be deepened in their study. In this work, an experimental investigation was conducted in order to explore the relationship between spatial non-uniformity, temporal instability, and the design features and components of a large-scale solar simulator based on metal halide lamps. The evaluation was based on the standard performance requirements of solar simulators, and various parameters were considered, including the geometry of the reflectors, the distance between reflectors, and the height of the lamps. In addition, the forces and deformations of the complete structure of the simulator, as well as the effects of the lamp orientation and the type of electrical supply, were analyzed. Based on the evaluation results of the design features and components, a simulator solar with an illuminated area of 1.7 m x 1.8 m was designed, constructed, and experimentally tested. A simulator class C was achieved, covering an area of 0.50 m x 0.50 m. The performance of the solar simulator was validated by experimental tests performed on commercial photovoltaic modules.

Distinguishing carrier transport and interfacial recombination at perovskite/transport-layer interfaces using ultrafast spectroscopy and numerical simulation

In perovskite solar cells, photovoltaic action is created by charge transport layers (CTLs) either side of the light-absorbing metal halide perovskite semiconductor. Hence, the rates for desirable charge extraction and unwanted interfacial recombination at the perovskite-CTL interfaces play a critical role for device efficiency. Here, the electrical properties of perovskite-CTL bilayer heterostructures are obtained using ultrafast terahertz and optical studies of the charge carrier dynamics after pulsed photoexcitation, combined with a physical model of charge carrier transport that includes the prominent Coulombic forces that arise after selective charge extraction into a CTL, and cross-interfacial recombination. The charge extraction velocity at the interface and the ambipolar diffusion coefficient within the perovskite are determined from the experimental decay profiles for heterostructures with three of the highest-performing CTLs, namely C60, PCBM and Spiro-OMeTAD. Definitive targets for the further improvement of devices are deduced: fullerenes deliver fast electron extraction, but suffer from a large rate constant for cross-interface recombination or hole extraction. Conversely, Spiro-OMeTAD exhibits slow hole extraction but does not increase the perovskite’s surface recombination rate, likely contributing to its success in solar cell devices. Published by the American Physical Society 2024

Synthesis and characterization of novel double perovskite K2AgBiBr6

Over the past few years, Lead-free halide double perovskites have attracted a tremendous attention such that it is demonstrated by the power conversion efficiency's sharp increase of over 25 %. It has also stimulated a widespread application of halide metal perovskites in other fields, such as light-emitting diodes, field-effect transistors, detectors, and lasers. Double perovskites have been put forth as an alternative to hybrid lead halide perovskites in the last decade because of their efficiency in doing away with the existing toxicity and instability. It is probably the first attempt, to date, that lead-free halide double perovskite K2AgBiBr6 has been made with a cheap, easy-to-use solution-state reaction method. To determine their structure, single crystal X-ray diffraction and PXRD analysis have been employed. The synthesized K2AgBiBr6 adopts the cubic structure with Fm‾3m symmetry and lattice parameters of a = 6.606 (9) Å at room temperature, according to the diffraction result. Energy dispersive X-ray spectroscopy (EDX), elemental mapping, and scanning electron microscopy (SEM) have all been employed to analyze the morphology and elemental composition. Elements including K, Bi, Ag, and Br have been confirmed to be present in the synthesized sample by the EDX technique. For K2AgBiBr6, the 2.859 eV (indirect) and 3.076 eV (direct) bandgaps have been estimated by employing the UV–Vis absorption spectra. Furthermore, the K2AgBiBr6 double perovskite nanocrystal's thermogravimetric analysis/differential thermal and differential scanning analysis (TG/DTA and DSC) curves at 20–800 °C have been measured. An analysis has been conducted on the mechanism of thermal decomposition of synthesized double perovskite. This work demonstrates great promise for future band gap engineering-based photovoltaic and other optoelectronic applications, and it offers a novel path to obtaining premium K2AgBiBr6 double perovskite.

Discerning the Structure-Photophysical Property Correlation in Zero-Dimensional Antimony(III)-Doped Indium(III) Halide Hybrids.

Zero-dimensional (0D) metal halide hybrids incorporating optically emissive Sb3+ dopants have received huge research attention as a result of dopant-based visible emission for lighting and scintillation applications. Indeed, there have been a plethora of reports on Sb3+ doping of indium halide (In-X)-based 0D hybrids that show strong dopant emission with varied emission wavelengths (λem) and photoluminescence quantum yields (PLQYs). However, discerning the structure-luminescence relation in these 0D-doped hybrids remains challenging because it necessitates exquisite synthetic control on the local metal (dopant) halide geometry/site asymmetry. Demonstrated here is synthetic control that allows tuning of the local metal halide geometry of the Sb3+ dopants in 0D In-X hybrids utilizing five different organic cations. Experimental analysis of the series of Sb3+-doped In-X hybrids reveals a strong correlation between the extent of local metal halide geometry distortion and their photophysical properties (λem and PLQY). Density functional theory calculations of the doped compounds, characterizing ground- and excited-state structural distortions and energetics, reveal the origin of the extent of luminescence behavior. The experimental-computational results reported herein unravel the operative structure-luminescence relation in 0D Sb3+-doped In-X hybrids, provide insight into the emission mechanism, and open up avenues toward rational synthesis of strongly emissive materials with desired emission color for targeted applications.

Supramolecular Assembly of Cesium Copper Iodine Resulting in Rich Emission Properties

AbstractCrown ether‐assisted supramolecular assembly is a robust strategy for manipulating low‐dimensional metal halides. In this study, the supramolecular assembly of 0D‐Cs3Cu2I5 is presented. Upon the addition of 15‐crown‐5 (15C5) to Cs3Cu2I5, 15C5 immediately coordinates with Cs+ to form the cone‐shaped [(15C5)Cs]+. Simultaneously, one of the iodine atoms is removed from the [Cu2I5]3‐ cluster, resulting in the formation of a sub‐planar rhombic [Cu2I4]2− unit. This process leads to white emission, specifically [(15C5)Cs]2[Cu2I4], which exhibits a photoluminescence quantum yield (PLQY) close to unity. The [(15C5)Cs]+ further reacts with 15C5 to form the sandwich‐type cationic structure [(15C5)2Cs]+, accompanied by the generation of red emission [(15C5)2Cs]2[Cu2I4]. By carefully controlling the amount of 15C5, various emission composites can be achieved, particularly tunable white emission. The assembly process is reversible. The pristine Cs3Cu2I5 can be recovered after thermal curing because of the volatility of crown ether and the weak Cs‐crown ether bond. Theoretical calculations have demonstrated that the coordination of the crown ether primarily affects the energy level, leading to changes in the excited state and photophysical properties. The applications in anticounterfeiting and LED phosphors have been demonstrated. This work provides a new approach for the development of low‐dimensional copper halides with promising applications in optoelectronics.

Single-detector multiplex imaging flow cytometry for cancer cell classification with deep learning.

Imaging flow cytometry, which combines the advantages of flow cytometry and microscopy, has emerged as a powerful tool for cell analysis in various biomedical fields such as cancer detection. In this study, we develop multiplex imaging flow cytometry (mIFC) by employing a spatial wavelength division multiplexing technique. Our mIFC can simultaneously obtain brightfield and multi-color fluorescence images of individual cells in flow, which are excited by a metal halide lamp and measured by a single detector. Statistical analysis results of multiplex imaging experiments with resolution test lens, magnification test lens, and fluorescent microspheres validate the operation of the mIFC with good imaging channel consistency and micron-scale differentiation capabilities. A deep learning method is designed for multiplex image processing that consists of three deep learning networks (U-net, very deep super resolution, and visual geometry group 19). It is demonstrated that the cluster of differentiation 24 (CD24) imaging channel is more sensitive than the brightfield, nucleus, or cancer antigen 125 (CA125) imaging channel in classifying the three types of ovarian cell lines (IOSE80 normal cell, A2780, and OVCAR3 cancer cells). An average accuracy rate of 97.1% is achieved for the classification of these three types of cells by deep learning analysis when all four imaging channels are considered. Our single-detector mIFC is promising for the development of future imaging flow cytometers and for the automatic single-cell analysis with deep learning in various biomedical fields.

Autonomous Control of Ion Migration at α‐FAPbI3 Heterointerfaces via Interfacial‐Self‐Assembled 2D Perovskite

AbstractHarmonizing homogeneity in charge distribution within metal halide perovskite solar cells is essential for maintaining device quality. The adsorption of ions from perovskites onto the electron transport layer leads to the creation of redistributed space‐charge regions (SCR), which facilitate halide segregation and ionic migration, resulting in charge imbalances and diminished extraction capability at the interface. The research examines the intricate interplay between SCRs affecting iodide oxidation and their impact on photovoltaics, uncovering a previously overlooked aspect that the influence of ionic accumulation on electronic charge uniformity. A paradox is identified that electronic charge accumulation at interfaces improves initial open‐circuit voltage, however, compromises stability with a collapsed charge distribution. To address this issue, ion conduction is regulated by utilizing a self‐assembled 2D perovskite resulting from cationic exchange with a low migration barrier at the buried interface, thereby mitigating halide segregation and charge inhomogeneity. This approach exhibits a power conversion efficiency (PCE) of 24.38% with a fill‐factor of 84% and maintains 91.87% of the initial PCE for a duration of 2070 h.

Halide tuning in derivative organic–inorganic perovskites, MAPb(Br1-xClx)3 (x = 0–1): exploring structural, optical and vibrational characteristics

Organic–inorganic metal halide perovskites (OIMHP’s), particularly CH3NH3PbX3 (X = I, Br, Cl) and their derivatives shows favorable properties for energy harvesting such as high absorption coefficients, adjustable band gaps, and low charge recombination rate. The structure and hence nature of bonding between different atoms of these perovskites is known to affect their properties significantly. Tuning of band gap can be achieved in these systems with the help of compositional variation. These systems are studied extensively in the single halide compositions (MAPbI3, MAPbBr3 and MAPbCl3); while, their derivatives seem to have gained less attention though being important for various applications. So, in this work, halide tuning is achieved in derivative perovskite, MAPb(Br1-xClx)3 (x = 0 to 1) and further studied for structural and optical properties along with vibrational properties using X-ray diffraction (XRD), diffuse reflectance spectroscopy, and Raman spectroscopy techniques, respectively. A decrease in the lattice parameter is observed as the Chlorine content increases in the MAPb(Br1-xClx)3 (x = 0 to 1) perovskite. The substitution of Chlorine with Bromine also results in significant increase in the band gap value. In contrast to previous reports, it was clearly observed that the Urbach energy strongly depends on the composition. For the first time, appearance of two features for torsional mode of methylammonium (MA) is discussed even at room temperature, indicative of disorder. It is observed that although the band gap tuning is achieved with the help of halide mixing (Br and Cl), it is also found to introduce disorder in the intermediate compositions; while, the stability increases toward Chlorine compositions. Interestingly, the information of disorder is found to be contained in both the global as well as local measurements which opens up new pathways for studying these materials. This study will lay down a pathway for better understanding of key properties of these hybrid mix halide perovskites which are promising material for futuristic energy applications.

Multi-Axial Self-Driven X-Ray Detection by a Two-Dimensional Biaxial Hybrid Organic-Inorganic Perovskite Ferroelectric.

Metal halide perovskite ferroelectrics combining spontaneous polarization and excellent semiconducting properties is an ideal platform for enabling self-driven X-ray detection. However, achievements to date have been only based on uniaxiality, which increases the complexity of device fabrication. Multi-axial ferroelectric materials have multiple equivalent polarization directions, making them potentially amenable to multi-axial self-driven X-ray detection, but the report on these types of materials is still a huge blank. Herein, a high-quality (BA)2(EA)2Pb3I10 (1) biaxial ferroelectric single crystal was successfully grown, which exhibited significant spontaneous polarization along the c-axis and b-axis. Under X-ray irradiation, bulk photovoltaic effect (BPVE) was exhibited along both the c-axis and b-axis, with open circuit voltages (Voc) of 0.23 V and 0.22 V, respectively. Then, the BPVE revealed along the inversion of polarized direction with the polarized electric fields. Intriguingly, due to the BPVE of 1, 1 achieved multi-axial self-driven X-ray detection for the first time (c-axis and b-axis) with relatively high sensitivities and ultralow detection limits (17.2 nGyair s-1 and 19.4 nGyair s-1, respectively). This work provides a reference for the subsequent use of multi-axial ferroelectricity for multi-axial self-driven optoelectronic detection.

Separation of halogens and recovery of heavy metals from secondary copper smelting dust

The separation of halogens and recovery of heavy metals from secondary copper smelting (SCS) dust using a sulfating roasting−water leaching process were investigated. The thermodynamic analysis results confirm the feasibility of the phase transformation to metal sulfates and to gaseous HF and HCl. Under the sulfating roasting conditions of the roasting temperature of 250 °C and the sulfuric acid excess coefficient of 1.8, over 74 wt.% of F and 98 wt.% of Cl were volatilized into flue gas. Approximately 98.6 wt.% of Zn and 96.5 wt.% of Cu in the roasting product were dissolved into the leaching solution after the water leaching process, while the leaching efficiencies of Pb and Sn were only 0.12% and 0.22%, respectively. The mechanism studies indicate the pivotal effect of roasting temperature on the sulphation reactions from various metal species to metal sulfates and the salting out reactions from various metal halides to gaseous hydrogen halides.