Cl Doping Research Articles

Kinetic and thermodynamic synergy of spongiform nanostructure and alien dopants enables promoted sodium-ion transfer for high-performance sodium storage

Chlorine-doped spongiform TiO 2 /C composite is synthesized by an NH 4 Cl-assisted annealing strategy with zinc alginate and commercial TiO 2 nanoparticles as precursors, demonstrating superior sodium-ion diffusion kinetics and reaction thermodynamics with well-designed spongiform structure and rational element doping. • A novel NH 4 Cl-assisted annealing strategy is developed to prepare ZATC-Cl. • The spongiform structure of ZATC-Cl results in fast sodium-ion diffusion kinetics. • Cl dopants in ZATC-Cl achieve preferable sodium-ion reaction thermodynamics. • ZATC-Cl delivers remarkable sodium storage performance. To address the bottlenecks of sluggish sodium-ion transfer processes, the electrode materials of sodium-ion battery (SIB) are always designed from the viewpoints of sodium-ion diffusion kinetics or reaction thermodynamics for high-performance sodium storage. Herein, starting with spongiform TiO 2 /C composite derived from zinc alginate, a NH 4 Cl-assisted annealing strategy is developed to prepare chlorine-doped spongiform TiO 2 /C composite (ZATC-Cl). Acting as the anode of SIBs, the obtained ZATC-Cl delivers excellent sodium storage performance with a high reversible capacity of 352.4 mAh g −1 at 50 mA g −1 , a superior rate capability of 246.8 mAh g −1 at 2 A g −1 and a considerable high-rate cycling performance of 248.5 mAh g −1 at 2 A g −1 for 1000 cycles. It is believed that the unique spongiform structure and ultra-small sized TiO 2 particles in ZATC-Cl can achieve fast sodium-ion insertion/extraction, realizing rapid sodium-ion diffusion kinetics. Moreover, as well evidenced by experiment results and theoretical calculations, the Cl dopants introduced in ZATC-Cl can provide more active sites for robust sodium-ion chemical adsorption, optimizing sodium-ion reaction thermodynamics. This study demonstrates an alternative approach to improve the sodium storage capability of TiO 2 anodes by the synergistically engineering the morphological and structural properties and manipulating the surface active sites, from both kinetic and thermodynamic viewpoints of sodium storage processes.

Simultaneous electrical and defect engineering of nickel iron metal-organic-framework via co-doping of metalloid and non-metal elements for a highly efficient oxygen evolution reaction

Metal-organic frameworks (MOFs) are promising electrocatalysts for oxygen evolution reaction (OER) due to their large amounts of active sites reacting with water molecules and desired adsorption/desorption characteristics with oxygen intermediate. However, the intrinsically low electrical conductivity of MOFs hinders their commercialization for the highly efficient OER catalyst. Here, we report 2D morphological NiFe MOF electrocatalyst co-doped with metalloid and non-metal elements for the enhanced OER performances. Te metalloid incorporation on MOFs facilitates electron transfer from transition metals of MOFs to embedded metalloids, which improves OER kinetics enabling favorable adsorption of oxygen intermediate on the surface of the electrocatalyst. Incorporated halogen Cl element could effectively induce defects on MOF as leach out from the surface of electrocatalyst during OER, allowing more active sites exposed to reactants. With the synergistic effect of metalloid (Te) and halogen (Cl) doping on NiFe MOF, the Te and Cl co-doped NiFe MOF growth on Ni foam (NF) present an excellent OER property requiring low overpotential for 224 mV at 30 mA cm−2 in alkaline condition and long-term stability over 120 h.

Modulating the Electronic Structure of Nickel Sulfide Electrocatalysts by Chlorine Doping toward Highly Efficient Alkaline Hydrogen Evolution.

The exploration of indurative and stable low-cost catalysts for hydrogen evolution reaction (HER) is of great importance for hydrogen energy economy, but it still faces challenges. Herein, we report a Cl-doped Ni3S2 (Cl-Ni3S2) nanoplate catalyst vertically grown on Ni foam with outstanding activity and durability for HER, which only requires an overpotential of 67 mV to reach a current density of 10 mA cm-2 in alkaline media and exhibits negligible degradation after 30 h of operation. Both the advanced X-ray absorption fine structure (XAFS) and density functional theory (DFT) calculation validate that Cl doping can optimize the electronic structure and the intrinsic activity of Ni3S2. This study devoted to the revelation of the impact of ionic doping on the activity of catalysts at the atomic scale can provide the direction for the rational design of novel and advanced HER electrocatalysts.

Improved Thermal Stability and Enhanced Thermoelectric Properties of p-Type BaCu2Te2 by Doping of Cl.

Doping in semiconductors is a widely implemented strategy for manipulation of carrier concentration, which is a critical parameter to regulate the thermoelectric performance. Stoichiometric BaCu2Te2 shows high hole concentration and unstable transport properties owing to the inherent Cu vacancy and dynamic precipitation behavior. In this work, Te has been partially substituted by Cl in BaCu2Te2 to suppress the overhigh hole concentration. Due to the high electronegativity of Cl, strong Cl-Cu bonds can significantly inhibit the Cu migration and the consequent dynamic precipitation. Meanwhile, nano-precipitate BaCl2 distributes in the grain boundary, acting as ionic blocking layers. Therefore, the thermal stability of the samples can be essentially improved via chemical bonding strengthening and grain boundary engineering. In terms of thermal transport, the introduced point defects and second phase strengthen the short-wavelength and medium-wavelength phonon scattering, leading to further reduced thermal conductivity. Eventually, the repeatable ZT value of BaCu2Te1.98Cl0.02 reached 1.22 at 823 K, which is higher by 19.6% compared with 1.02 of pristine BaCu2Te2. The average ZTs of BaCu2Te2-xClx (x = 0, 0.02, 0.04, and 0.06) in the temperature range of 323-823 K are 0.737 for x = 0.02, 0.689 for x = 0.04, and 0.667 for x = 0.06, which are 24.6, 17.2, and 13.4% higher than the average ZT of 0.588 corresponding to the undoped sample, respectively. The study shows that synergetic enhancements of thermal stability and thermoelectric properties can be achieved by strengthening chemical bonding and constructing ionic blocking layers in the grain boundary, which can be applied to other fast-ionic conductor thermoelectric materials.

Improved two-step photon absorption current by Cl-doping in ZnTeO-based intermediate band solar cells with n-ZnS layer

We report the improved photocurrent induced by two-step photon absorption (TSPA) in the intermediate band solar cells (IBSCs) with a n-ZnS/ZnTe/ZnTeO/ZnTe/p-ZnTe structure using Cl-doped ZnTeO. In the IBSC with an undoped ZnTeO, the TSPA current is not observed at room temperature but it is significantly improved by using Cl-doped ZnTeO. Temperature and excitation intensity dependent photoluminescence (PL) spectra reveal the high activation energy of Cl-donor, and the observed activation temperature by PL measurements is consistent with the temperature where the TSPA current starts to increase. The temperature dependence of the open circuit voltage of the IBSC using Cl-doped ZnTeO also supports that the Cl doping in the ZnTeO layer introduces electrons into the intermediate band.

Halide (X = I, Br, Cl) doping to tune the electronic structure for conversion of Pb0.6Sn0.4Te into a high-performing thermoelectric material

The first report of a DFT study on halide (I, Br, Cl) doping in Pb0.6Sn0.4Te, a topological crystalline insulator reveals an opening of band gap and band convergence without breaking crystal mirror symmetry, leading to high thermoelectric performance.

Enhanced Thermoelectric Properties of Inse Through Simultaneous Increase in Electrical Conductivity and Seebeck Coefficient by Cl Doping

Enhanced Thermoelectric Properties of Inse Through Simultaneous Increase in Electrical Conductivity and Seebeck Coefficient by Cl Doping

Properties and improvements of chlorine-doped methylamine-based perovskites

Metal halide perovskite (MHP) has been widely used in optoelectronic devices such as solar cells in recent years due to their high absorption coefficients, long-range charge carrier diffusion lengths, and adjustable band gap, which is expected to achieve commercial application. Methylammonium lead iodide (MAPbI<sub>3</sub>) has been fully investigated as a standard perovskite component, however, due to the low formation energy of polycrystalline films fabricated by wet chemical method, crystal defects (including interface and grain boundary defects) are generally inevitable, which is a principal factor leading to phase transition. Therefore, reducing the defect density of perovskite is a prominent approach to improve the stability of perovskite. Although defect passivation is one of the most commonly used methods to fabricate efficient perovskite solar cells (PSCs), the relatively weak secondary bond between molecular passivation group and perovskite crystal may bring difficulties to the application of practical devices, particularly when operating under harsh environments, such as high temperature, humidity, and ultraviolet light. Therefore, improving the intrinsic structure stability of the perovskite via changing its composition can be an effective way. Although perovskites containing chlorine precursors have been empolyed in solar cells device, how chloride ions affect the structural and electronic properties of these films was not understood yet. In this work, two-phase perovskite (MAPbI<sub>2</sub>Cl) was fabricated by one-step spin coating with methylamine chloride (MACl) and lead iodide (PbI<sub>2</sub>) as precursors. As a result, chloride (Cl) doping can superiorly induce perovskite crystallization and thus stabilize the MAPbI<sub>3</sub> lattice. The Cl doped perovskite layer shows lower defect density, and compared with the original MAPbI<sub>3</sub> film, the carrier lifetime of MAPbI<sub>2</sub>Cl is increased by 7 times. Simultaneously, both of PCE and operational stability have been largely improved with PCE increased from 11.41% to 13.68%. There is no obvious degradation in the maximum power point output for nearly 8000 seconds in ambient conditions.

Localized Electron Density Redistribution in Fluorophosphate Cathode: Dangling Anion Regulation and Enhanced Na‐Ion Diffusivity for Sodium‐Ion Batteries (Adv. Funct. Mater. 4/2022)

Anionic Doping In article number 2109694, Hong Yu, Cheng-Feng Du, Xing-Long Wu, and co-workers develop Cl-doped Na3V2(PO4)2O2F (NVPO2−xClxF) as superior cathode material for sodium-ion batteries. In NVPO2−xClxF, Cl doping tunes the electronic structure and causes the electron redistribution on vanadium center/dangling anions. As a result, a revised redox behavior of vanadium and increased Na+- diffusivity/electrochemical properties are achieved.

Understanding the role of Cl doping in the oxygen evolution reaction on cuprous oxide by DFT.

Designing highly active and earth-abundant oxygen evolution reaction (OER) electrocatalysts for electrochemical water splitting remains a challenge. Recently, Cl-doped Cu2O has emerged as a very promising non-noble-metal electrocatalyst candidate for the OER. However, the mechanism of the OER catalyzed by Cl-doped Cu2O has not been explored systematically. Herein, a comprehensive density functional theory (DFT) study is employed to study the role of Cl doping via comparing the OER on pure and Cl-doped Cu2O surfaces with/without Cu vacancies. Our results reveal that Cl doping increases the adsorption ability of Cu2O(111) by providing an excess electron, while a Cu vacancy decreases its adsorption ability by changing the geometric structure of the adsorption sites and the electronic structures. Cl-Cu2O(111) (η = 0.58 V) and VCu-Cl-Cu2O(111) (η = 0.46 V) have comparable or even better OER activity than those of widely used OER electrocatalysts such as the IrO2 catalyst (η = 0.56 V). It is facile to have a Cu vacancy when Cu2O(111) is doped with Cl because of a large strain introduced by Cl doping. Thus, VCu-Cl-Cu2O(111) should be the most feasible catalyst for the OER catalyzed by Cl-doped Cu2O material. The dual role of Cl doping is that it not only increases the OER activity but also helps to form a Cu vacancy. The results show that Cu2O(111) activity can be greatly enhanced via electronic and geometric structure modulation, which is helpful for the design of more efficient Cu2O-based catalysis.

Enhancement of thermoelectric performance for n-type PbS via synergy of CuSbS2 alloying and Cl doping

Lead sulfide has attracted extensive attention as an outstanding thermoelectric material with practical energy conversion applications at intermediate temperature scope due to its cost-effectiveness and earth-abundant constituent elements. However, the naturally low carrier concentration and high thermal conductivity greatly restrict the thermoelectric performance of PbS-based materials. Herein, we present a significantly promoted thermoelectric performance in n-type PbS through synergistically promoting the electrical conductivity and suppressing lattice thermal conductivity with Cl doping and CuSbS2 alloying. The alloying with CuSbS2 lowers lattice thermal conductivity of PbS, which is essentially ascribed to point defect scattering. While the substitution of Cl for S in lattice significantly increases the Hall carrier concentration and carrier mobility, which prominently boosts electrical conductivity and thus results in high power factor of ~1.38 mW/mK2 at 723 K. Finally, compound with the nominal composition of (PbS0.98Cl0.02)0.95(CuSbS2)0.05 reaches a peak zT of ~0.76 at 773 K.

N -type electrical conduction in SnS thin films

Tin monosulfide (SnS) usually exhibits p-type conduction due to the low formation enthalpy of acceptor-type defects, and as a result n-type SnS thin films have never been obtained. This study realizes n-type conduction in SnS thin films for the first time by using RF-magnetron sputtering with Cl doping and sulfur plasma source during deposition. N-type SnS thin films are obtained at all the substrate temperatures employed in this study (221-341 C), exhibiting carrier concentrations and Hall mobilities of ~2 x 10 18 cm-3 and 0.1-1 cm V-1s-1, respectively. The films prepared without sulfur plasma source, on the other hand, exhibit p-type conduction despite containing a comparable amount of Cl donors. This is likely due to a significant amount of acceptor-type defects originating from sulfur deficiency in p-type films, which appears as a broad optical absorption within the band gap. The demonstration of n-type SnS thin films in this study is a breakthrough for the realization of SnS homojunction solar cells, which are expected to have a higher conversion efficiency than the conventional heterojunction SnS solar cells.

Long-Range Cationic Order Collapse Triggered by S/Cl Mixed-Anion Occupancy Yields Enhanced Thermoelectric Properties in Cu5Sn2S7

To investigate pathways to adjust the charge carrier concentration and optimize the thermoelectric properties, we characterized structural properties, thermal stability, and thermoelectric performance of pristine and Cl-doped Cu5+εSn2−εS7. We demonstrate that Cl doping in Cu5Sn2S7-type monoclinic compounds induces a collapse of the long-range cationic ordering, ultimately leading to a sphalerite-type cubic phase characterized by ordered [Sn(S,Cl)4]x clusters. The change in crystal structure symmetry upon Cl doping is analyzed by Rietveld refinements against X-ray powder diffraction data, transmission electron microscopy, Mössbauer and X-ray absorption spectroscopy, and low- and high-temperature transport property measurements. The thermoelectric properties of the so-obtained cubic sphalerite Cu5+εSn2−εS7–yCly (0 ≤ ε ≤ 0.133, y = 0.35, 0.70) are strongly enhanced with respect to the undoped Cu5Sn2S7: the power factor improves slightly while both electronic and lattice contributions to the thermal conductivity are reduced. Overall, single-phase Cl-doped Cu5.133Sn1.866S7–yCly (y = 0.35, 0.70) compounds exhibit high thermoelectric performance, reaching a maximum ZT of 0.45 at 670 K.

Facilely Prepared Cl-Doped Graphene as an Efficient Anode for the Electrochemical Catalytic Degradation of Acetaminophen.

The application of electrochemical catalytic oxidation in wastewater treatment with powerful Cldoped graphene as an anode has been discussed as a novel approach to degrade acetaminophen effectively. The characteristics of Cl-doped graphene that were related to Cl loading content and microscopic morphology were analyzed by using several instruments, and the defects created by Cl doping were identified. Quenching experiments and electron paramagnetic resonance detection were proposed to clarify the mechanism underlying the production of active free radicals by Cldopedgraphene. The degradation results indicated that efficiency increased with the percentage of Cl atoms doped into the graphene. The best degradation efficiency of acetaminophen could reach 98% when Cl-GN-12 was used. In the process of electrocatalytic oxidation, O•-₂, and active chlorine, as the main active species, persistently attacked acetaminophen into open-ring intermediates, such as 4-chlororesorcinol, and finally into CO₂ and H²O.

Localized Electron Density Redistribution in Fluorophosphate Cathode: Dangling Anion Regulation and Enhanced Na‐Ion Diffusivity for Sodium‐Ion Batteries

AbstractPolyanionic transition metal polyphosphate (TMPO)‐type Na3V2(PO4)2O2F (NVPO2F) is promising as cathode for large‐scale sodium‐ion batteries (SIBs) on account of its considerable capacity and highly stable structure. However, the redox of transition metal and phase transitions along with the (de)intercalation of Na+ lead to its slow kinetics and inferior rate performance. Herein, chlorine (Cl) is applied as a heteropical dopant to obtain Cl‐doped NVPO2F (NVPO2−xClxF) cathode material for SIBs. Density functional theory investigation reveals that Cl doping tunes the localized electronic density and structure in NVPO2F lattice, causing the electron redistribution on vanadium center and dangling anions. Hence, the NVPO2−xClxF cathode exhibits a revised redox behavior of vanadium for Na+ extraction/insertion, increases Na+ diffusion rate, as well as lowers charge transfer resistance. A Na+ storage mechanism of reversible transformations between three phases and V4+/V5+ redox couple for NVPO2−xClxF cathode is verified. The NVPO2−xClxF cathode reveals a high rate capacity of ≈63 mAh g−1 at 30C and great cycle stability over 1000 cycles at 10C. More importantly, outstanding rate property (314 Wh kg−1 at 5850 W kg−1) and cycling capability are obtained for the NVPO2−xClxF//3DC@Se full cell. This study demonstrates a brand‐new strategy to prepare advanced cathode materials for superior SIBs.

Healing soft interface for stable and high-efficiency all-inorganic CsPbIBr2 perovskite solar cells enabled by S-benzylisothiourea hydrochloride

Interfacial regulation to heal the soft lattice induced defective nanostructured surfaces of perovskite films plays a crucial role in determining the stability and efficiency of perovskite solar cells (PSCs). Herein, we report a facile method to strengthen and passivate the inorganic PbI2-excess CsPbIBr2 surface with a multifunctional S-benzylisothiourea hydrochloride (SBTCl), which not only significantly reduces the detrimental defects through interaction between electron-donating groups and defects (as well as Cl doping as lattice “glue”) but also enables straightway unobstructed hole extraction and transfer arising from the reduced work function. Consequently, a higher efficiency of 10.56% with an open-circuit voltage of 1.327 V than control device with 7.72%-efficiency is obtained for inorganic CsPbIBr2 PSC free of hole transporting material, which is one cutting-edge value in this kind of PSC. In addition, the high hydrophobicity of SBTCl passivator hinders the permeation of moisture into perovskite film, resulting in improved long-term air-stability after storage in 5% relative humidity (RH) without encapsulation over 110 days and persistent light irradiation over 16 h in 50% RH condition.

Gas selectivity regulation of monolayer SnS by introducing nonmetallic dopants: A combined theoretical and experimental investigation

The group-IV monochalcogenide of SnS is explored promising for gas sensor applications due to its unique two-dimensional puckered monolayer and superior oxidation resistance. This work focuses on the gas selectivity regulation of SnS monolayer with adjustable doping. To this end, detailed studies for the effects of nonmetallic dopants (X) of Si, P, or Cl in SnS lattice on the selective adsorption of NO2, NH3, SO2 are first performed by first-principles calculations. It reveals that the SnS monolayers with Si and P doping exhibit stronger adsorption capability and rapid recovery characteristic towards NH3 and SO2 at room temperature, respectively, while Cl-doped SnS could realize the reversible detection of NO2 at elevated temperature. These theoretical findings were further verified in experiment. Gas-sensing evaluations show the obvious gas selectivity of SnS with different doping of Si, P and Cl towards NH3, SO2, and NO2, respectively. The response magnitude exhibited by the doped SnS is revealed to be positively correlated with the calculated electron transfer. In terms of recovery performance of the doped SnS, intrinsic recovery characteristic could be predicted by the calculation on recovery time, while the measured recovery time reflects the combined effect of material characteristic and environmental factors.

Modification of compact TiO2 layer by TiCl4-TiCl3 mixture treatment and construction of high-efficiency carbon-based CsPbI2Br perovskite solar cells

In the construction of high performance planar perovskite solar cells (PSCs), the modification of compact TiO2 layer and engineering of perovskite/TiO2 interfaces are essential for efficient electron transfer and retarded charge recombination loss. In this work, a facile and effective strategy is developed to modify the surface of compact TiO2 layer by TiCl4-TiCl3 mixture treatment. Compared with conventional sole TiCl4, the TiCl4-TiCl3 treatment takes the advantage of accelerated and controlled hydrolysis of TiCl3, therefore TiO2 with dominating anatase phase and moderate roughness is obtained to facilitate the growth of CsPbI2Br perovskite layer with high quality. Furthermore, the oxidation-driven hydrolysis of TiCl3 component results in surface Cl doping that facilitates interfacial electron transfer with retarded recombination loss. The average power conversion efficiency (PCE) of carbon-based CsPbI2Br planar PSCs based on TiCl4-TiCl3 treatment increases to 14.18% from the intial 13.04% based on conventional sole TiCl4 treatment. The champion PSC exhibits a PCE of 14.46% (Voc = 1.28 V, Jsc = 14.21 mA/cm2, and FF = 0.794), which is one of the highest PCEs for carbon-based CsPbI2Br PSCs.

Enhancing Light Absorption and Prolonging Charge Separation in Carbon Quantum Dots via Cl-Doping for Visible-Light-Driven Photocharge-Transfer Reactions.

Limited light absorption beyond the UV region and rapid photocarrier recombination are critical impediments for the improved photocatalytic performance of carbon quantum dots (CQDs) under visible-light irradiation. Herein, we demonstrate single-step microwave-assisted syntheses of O-CQDs (typical CQDs terminated by carboxylic and hydroxyl functional groups) from a sucrose precursor and Cl-doped CQDs (Cl-CQDs) from a sucralose precursor in short reaction times and without using obligatory strong acids for Cl doping. The doping of Cl into the CQDs is observed to widen the absorption range and facilitate an enhanced separation of photoexcited charge carriers, which is confirmed by the results of optical absorption, photothermal response, and pump-probe ultrafast transient absorption spectroscopy measurements of the O-CQDs and Cl-CQDs. The photoexcited charge carriers with their longer lifetimes in Cl-CQDs enabled the quick degradation of methylene blue dye, rapid conversion of Ag+ ions to metallic Ag nanoparticles on the CQD surfaces, and reduction of GO to a well-dispersed rGO through the photoelectron transfer reactions under visible-light irradiation. The facile Cl doping strategy, hybridization of Ag nanoparticles or rGO to CQDs, and the elevated charge separation mechanism would open up new avenues in designing CQD-based materials for futuristic applications.

Tuning intrinsic defects in γ-CuI by cation and anion doping

γ-CuI is a promising scintillator owing to the ultrafast decay time of 130 ps contributed by the near-band-edge emission. The luminescence properties of the γ-CuI are directly related to its intrinsic defects, such as Cu and I vacancies. In this context, tuning the intrinsic defects by cation and anion doping was proposed to improve the scintillation performance of γ-CuI. The structural properties of the dopants, including Li, Na, Mg, F, Cl and Br, were investigated by first-principles calculations. The Li, Na and Mg atoms were calculated to occupy the Cu site. The Cl and Br atoms turned out to replace the I atoms. Importantly, the Cu vacancies were created by Cl and Br dopants, and the I vacancies were eliminated through Li, Na, Mg, Cl and Br doping. These theoretical results were demonstrated by photoluminescence and X-ray excited luminescence spectra.