Doping Modification Research Articles

Zn-Doped SnO2 Compact Layer for Enhancing Performance of Perovskite Solar Cells

Perovskite solar cells (PSCs) have been developing rapidly since they were discovered, and their excellent photoelectric properties have attracted wide attention from researchers. The compact layer is an important part of PSCs, which can transport electrons and block holes. SnO2 is an excellent and commonly used electron transport layer (ETL) material, and doping modification is an effective way to improve performance. Here, Zn with a similar radius to Sn has been introduced to the doping of the SnO2 compact layer to achieve the purposes of conductivity enhancement of the compact layer and followed photoelectric performance improvement of the device. Zn-SnO2 compact layers with different doping concentrations were prepared and applied to mesoporous architecture PSCs. When the doping content was 5%, the power conversion efficiency (PCE) of the device based on the Zn-SnO2 compact layer has increased from 9.08% to 10.21%, with an increase of 12.44%. The doping of SnO2 promotes its application in low-cost PSCs.

Combined Modifications for Effectively Improving the Photoelectrochemical Performance of Hematite Photoanode

As the photoanode material of photoelectrochemical (PEC) cells, hematite (Fe2O3) is a very promising candidate. Herein, the nanocoral‐like hematite film is designed using a simple hydrothermal method. The conductivity of the material improves by Ti ion doping, and a thin ZnFe2O4 film is deposited on the surface to form the type‐II heterostructure, which regulates the transport path of the carriers. At the same time, the FeOOH catalyst accelerates the oxygen evolution kinetics on the electrode surface. Finally, the photocurrent density of the TiFe2O3/ZnFe2O4/FeOOH photoanode reaches 1.93 mA cm−2 at 1.23 VRHE, and the open voltage is negatively shifted by 200 mV, compared with the Fe2O3 photoanode, down to 0.62 V. This work proves that element doping and surface modification improve the PEC performance by optimizing the transport path of carriers and increasing the reaction rate of oxygen evolution reaction.

Advances in engineering perovskite oxides for photochemical and photoelectrochemical water splitting

Solar-driven water splitting is an efficient process for converting solar energy into chemical energy. In this process, semiconductor materials are excited by solar energy to generate free electrons to participate in the water-splitting reaction. Among these semiconductor materials, inorganic perovskite oxides have a spatial structure that is easy to control and thereby lead to different energy band structures and photocatalytic properties. More importantly, perovskite oxides can be compounded with other organic/inorganic materials to promote charge separation and improve apparent quantum yield. However, the low solar-to-hydrogen conversion efficiency has not yet reached the requirements of practical applications. In this review, the fundamental principles of solar-driven water splitting based on perovskite materials are introduced according to the most recently published results. In addition, the innovative modification techniques for water splitting based on perovskite oxides have been summarized, focusing on the following methods: element doping, homo/heterojunction formation, Z-scheme, plasmon effect, dye sensitization, carbon enhancement, and surface modifications. Note that the applications in the visible light wavelength range have been described, with emphasis among all these modification materials. Furthermore, the recent water-splitting reaction systems for practical applications are briefly discussed. As a summary, we outline the challenges and potential utilization associated with visible light–driven water splitting based on perovskite oxides for future commercial applications. This review describes various modification methods to improve photochemical performance of perovskite oxides as well as illustrates the potential to employ perovskite oxides as a key material for the practical application of water splitting.

Modification of ordered mesoporous carbon for removal of environmental contaminants from aqueous phase: A review

Contamination of water bodies by potentially toxic elements and organic pollutants has aroused extensive concerns worldwide. Thus it is significant to develop effective adsorbents for removing these contaminants. As a new member of carbonaceous material families (activated carbon, biochar, and graphene), ordered mesoporous carbon (OMC) with larger specific surface area, ordered pore structure, and higher pore volume are being evaluated for their use in contaminant removal. In this paper, modification techniques of OMC were systematically reviewed for the first time. These include nonmetallic doping modification (nitrogen, sulfur, and boron) and the impregnation of nano-metals and metal oxides (iron, copper, cobalt, nickel, magnesium, and rare earth element). Reaction conditions (solution pH, reaction temperature, sorbent dosage, and contact time) are of critical importance for the removal performance of contaminants onto OMC. In addition, the pristine and modified OMC have been investigated for the removal of a range of contaminants, including cationic/anionic toxic elements and organic contaminants (synthetic dye, phenol, and others), and involving different and specific mechanisms of interaction with contaminants. The future research directions of the application of pristine and modified OMC were proposed. Overall, this review can provide sights into the modification techniques of OMC for removal of environmental contaminants.

Doping and Surface Modification Enhance the Applicability of Nanostructured Fullerene–MWCNT Hybrid Draped LiNi0.1Mg0.1Co0.8O2 as High Efficient Cathode Material for Lithium-Ion Batteries

Development of high performance cathode materials, layer-structured ternary LiNixCoyM1−x−yO2 cathode materials have attracted much attention owing to their larger capacity and higher energy density. Persistent efforts have been devoted to tackling certain issues like low electronic conductivity and poor structural stability. Dual strategy of Mg doping and surface modification of the cathode material was adopted to improve the performance of the battery. Fullerene–Multi-Walled Carbon Nanotube (MWCNT) hybrid draped LiNi0.1Mg0.1Co0.8O2 nanocomposite was synthesized by a simple chemical route. The fullerene–MWCNT hybrid modifies the surface of pristine LiNi0.1Mg0.1Co0.8O2 thereby improves the electrochemical performance and maintains the structural stability of the cathode material. Pristine LiNi0.1Mg0.1Co0.8O2 and LiNi0.1Mg0.1Co0.8O2/fullerene–MWCNT nanocomposite were studied using various advanced characterization techniques such as X-ray diffraction (XRD), Micro-Raman spectroscopy, Field Emission Scanning Electron Microscopy (FESEM), X-ray Photoelectron Spectroscopy (XPS), and High-Resolution Transmission Electron Microscopy (HRTEM). It is found that LiNi0.1Mg0.1Co0.8O2 particles retain their structural integrity after being enveloped with a fullerene–MWCNT hybrid. The electrochemical performance was investigated with cyclic voltammetry (CV), galvanostatic charge–discharge (GCD) test and electrochemical impedance spectroscopy (EIS). As prepared LiNi0.1Mg0.1Co0.8O2, when deployed in the form of LiNi0.1Mg0.1Co0.8O2/fullerene–MWCNT composite exhibits a high specific capacity of 208 mAh g−1. Fullerene–MWCNT hybrid draped LiNi0.1Mg0.1Co0.8O2 nanocomposite provides an effective Li+ and electron channel that significantly increased the Li-ion diffusion coefficient and reduced the charge transfer resistance. Besides,the lithium diffusion coefficient increased from 5.13 × 10–13 (Li/LiNi0.1Mg0.1Co0.8O2) to 8.313 × 10–13 cm2 s−1 due to the improved kinetics of Li insertion/extraction process in Li/LiNi0.1Mg0.1Co0.8O2 + fullerene–MWCNT cell.

Highly efficient BiVO4 single-crystal nanosheets with dual modification: phosphorus doping and selective Ag modification

BiVO4, a visible-light response photocatalyst, has shown tremendous potential because of abundant raw material sources, good stability and low cost. There exist some limitations for further applicaitions due to poor capability to separate electron–hole pairs. In fact, a single-component modification strategy is barely adequate to obtain highly efficient photocatalytic performance. In this work, P substituted some of the V atoms from VO4 oxoanions, namely P was doped into the V sites in the host lattice of BiVO4 by a hydrothermal route. Meanwhile, Ag as an attractive and efficient electron-cocatalyst was selectively modified on the (010) facet of BiVO4 nanosheets via facile photo-deposition. As a result, the obtained dually modified BiVO4 sheets exhibited enhanced photocatalytic degradation property of methylene blue (MB). In detail, photocatalytic rate constant (k) was 2.285 min−1 g−1, which was 2.78 times higher than pristine BiVO4 nanosheets. Actually, P-doping favored the formation of O vacancies, led to more charge carriers, and facilitated photocatalytic reaction. On the other hand, metallic Ag loaded on (010) facet effectively transferred photogenerated electrons, which consequently helped electron–hole pairs separation. The present work may enlighten new thoughts for smart design and controllable synthesis of highly efficient photocatalytic materials.

Dual-regulation effects of intramolecular doping and surface modification on carbon nitride towards efficient degradation of bisphenol A

A new photo-enzyme composite catalyst is prepared based on a dual-modification strategy that is the intramolecular doping of p-benzoquinone and following surface decoration of horseradish peroxidase (HRP) for g-C3N4. The fabricated CNBQ/HRP photo-enzyme composite catalyst can effectively break down bisphenol A (BPA) in water, which exhibits a maximal 7.78 times rate constant and 4.18 times mineralization efficiency relative to original g-C3N4. The investigation results reveal that the dual-regulation effect of the formed intramolecular donor-accepter structure and the photo-enzyme synergistic catalysis can be induced in CNBQ/HRP photo-enzyme composite catalyst, which promotes the high-efficiency separation of charge carriers and the production of •OH so as to dramatically enhance the catalytic degradation BPA performance. This work enriches and develops the modification method of g-C3N4-based catalytic system for treating persistent organic pollutants in water.

Enhancing Lithium Manganese Oxide Electrochemical Behavior by Doping and Surface Modifications

Lithium manganese oxide is regarded as a capable cathode material for lithium-ion batteries, but it suffers from relative low conductivity, manganese dissolution in electrolyte and structural distortion from cubic to tetragonal during elevated temperature tests. This review covers a comprehensive study about the main directions taken into consideration to supress the drawbacks of lithium manganese oxide: structure doping and surface modification by coating. Regarding the doping of LiMn2O4, several perspectives are studied, which include doping with single or multiple cations, only anions and combined doping with cations and anions. Surface modification approach consists in coating with different materials like carbonaceous compounds, oxides, phosphates and solid electrolyte solutions. The modified lithium manganese oxide performs better than pristine samples, showing improved cyclability, better behaviour at high discharge c-rates and elevated temperate and improves lithium ions diffusion coefficient.

Collaborative modification based on Ti-ion effectively improves the electrochemical performance of Ni-rich LiNi0.8Co0.1Mn0.1O2 cathode materials

Through the wet coating method combined with high temperature calcining, samples based on Ti element coating and doping collaborative modification at different temperatures were obtained respectively (NCM811-Ti450, NCM811-Ti650, and NCM811-Ti850). Tests have shown that the TiO2 coating layer was successfully coated on the surface of the pure sample (NCM811). Additionally, with the increase of sintering temperature, Ti element in the part of the coating layer diffused into the crystal structure of LiNi0.8Co0.1Mn0.1O2 to form doping modification, which reduced the mixing degree of lithium nickel and expands the diffusion channel of lithium-ion. The electrochemical performance of co-modified samples displayed better cyclic stability and rate performance. Besides, the EIS test shows that the samples obtained from the collaborative modification have higher DLi+, which is improved from 9.14 × 10−16 cm2s−1 (NCM811) to 5.66 × 10−15 cm2s−1 (NCM811-Ti850).

Engineered Graphitic Carbon Nitride-Based Photocatalysts for Visible-Light-Driven Water Splitting: A Review

Graphitic carbon nitride (g-C₃N₄), a polymeric semiconductor, has become a rising star for photocatalytic energy conversion because of its facile accessibility, metal-free nature, low cost, and environmentally benign properties. This work reviews the latest progress of g-C₃N₄-based materials in visible-light-driven water splitting to hydrogen. It begins with a brief history of g-C₃N₄, followed by various engineering strategies of g-C₃N₄, such as elemental doping, copolymerization, crystalline tailoring, surface engineering, and single-atom modification, for elevated photocatalytic water decomposition. In addition, the synthesis of g-C₃N₄ in different dimensions (0D, 1D, 2D, and 3D) and configurations of a series of g-C₃N₄-based heterojunctions (type II, Z-scheme, S-scheme, g-C₃N₄/metal, and g-C₃N₄/carbon heterojunctions) were also discussed for their improvement in photocatalytic hydrogen production. Lastly, the challenges and opportunities of g-C₃N₄-based nanomaterials are provided. It is anticipated that this review will promote the further development of the emerging g-C₃N₄-based materials for more efficiency in photocatalytic water splitting to hydrogen.

Development of Boron-Doped Mesoporous Carbon Materials for Use in CO2 Capture and Electrochemical Generation of H2O2.

Mesoporous carbon materials have been increasingly studied due to their large specific surface area and good chemical stability. Optimizing their functionality through a doping modification can broaden their application in many fields. Herein, a series of B-doped mesoporous carbon materials are prepared by a convenient hydrothermal synthesis using F127 as the template and boric acid as the boron source. The whole material preparation process meets the requirements of green chemistry. Notably, the prepared carbon materials not only exhibit good electrocatalytic oxygen reduction to hydrogen peroxide in alkaline media but also have an excellent CO2 adsorption capacity (up to 121.34 mg/g) at 303 K and atmospheric pressure. These results show that the prepared samples can be utilized as multifunctional materials for handling a variety of environmental issues.

HCl-Tolerant HxPO4/RuOx–CeO2 Catalysts for Extremely Efficient Catalytic Elimination of Chlorinated VOCs

Bulk metal doping and surface phosphate modification were synergically adopted in a rational design to upgrade the CeO2 catalyst, which is highly active but easily deactivated for the catalytic oxidation of chlorinated volatile organic compounds (Cl-VOCs). The metal doping increased the redox ability and defect sites of CeO2, which mostly promoted catalytic activity and inhibited the formation of dechlorinated byproducts but generated polychlorinated byproducts. The subsequent surface modification of the metal-doped CeO2 catalysts with nonmetallic phosphate completely suppressed the formation of polychlorinated byproducts and, more importantly, enhanced the stability of the surface structure by forming a chainmail layer. A highly active, durable, and selective catalyst of phosphate-functionalized RuOx-CeO2 was the most promising among all the metal-doped (Ru, Pd, Pt, Cr, Mn, Fe, Co, and Cu) CeO2 catalysts investigated owing to the prominent chemical stability of RuOx and its superior versatility in the catalytic oxidation of different kinds of Cl-VOCs and other typical pollutants, including dimethyl sulfide, CO, and C3H8. Moreover, the chemical stability of the catalyst, including its bulk and surface structural stability, was investigated by combining intensive treatment with HCl/H2O or HCl with subsequent ex situ ultraviolet-visible light Raman spectroscopy and confirmed the superior resistance to Cl poisoning of the phosphate-functionalized RuOx-CeO2. This work exemplifies a promising strategy for developing ideal catalysts for the removal of Cl-VOCs and provides a catalyst with the superior catalytic performance in Cl-VOC oxidation to date.

Doping effects of metal cation on sulfide solid electrolyte/lithium metal interface

Doping modification is usually used to improve the ionic conductivity of sulfide solid electrolytes, but its effects on the interface between the electrolyte/lithium (Li) metal seem not sufficiently studied and understood. In this work, the advantages and disadvantages of sulfide electrolyte doped with MoS 2 , ZnS, FeS 2 , SnS 2 and SiS 2 are systematically studied. The ab initio molecular dynamics (AIMD) calculations and experiments show that MoS 4 4- can preferentially replace the P 2 S 7 4- in Li 7 P 3 S 11 , thereby broadening Li + channels and creating Li vacancies to promote ion conduction. However, the doping of MoS 2 can lead to the introduction of Mo metal into the solid electrolyte/Li interface layer (SEI), resulting in the reduction of the SEI’s interface energy and migration rate of Li atoms at SEI, as well as the accumulation of electrons, thereby accelerating the thickening of the SEI and growth of Li dendrites. The doping results of different sulfides show that the critical current density is positively related to the resistivity of the doping element. The doping of non-metallic silicon will not cause a decrease in the critical current density. This work provides an important reference for the selection of solid electrolyte dopants and the construction of electrolyte/Li interface. • Metal cations doping of Li7P3S11 will replace P2S74- and increase ion conductivity. • Metallic Mo will reduce interface energy and increase Li diffusion barrier of SEI, accelerating Li dendrites growth. • Mo will turn SEI into a mixed conductor of ions and electrons, thus thickening SEI. • Critical current density is positively correlated with resistivity of the doping elements, rather than ion conductivity. • Non-metallic Si-doping will cause an increasement in electrochemical performance.

Advances and Prospects of High-Voltage Spinel Cathodes for Lithium-Based Batteries.

Insertion compounds have been dominating the cathodes in commercial lithium-ion batteries. In contrast to layered oxides and polyanion compounds, the development of spinel-structured cathodes is a little behind. Owing to a series of advantageous properties, such as high operating voltage (≈4.7V), high capacity (≈135mAh g-1 ), low environmental impact, and low fabrication cost, the high-voltage spinel LiNi0.5 Mn1.5 O4 represents a high-power cathode for advancing high-energy-density Li+ -ion batteries. However, the wide application and commercialization of this cathode are hampered by its poor cycling performance. Recent progress in both the fundamental understanding of the degradation mechanism and the exploration of strategies to enhance the cycling stability of high-voltage spinel cathodes have drawn continuous attention toward this promising insertion cathode. In this review article, the structure-property correlations and the failure mode of high-voltage spinel cathodes are first discussed. Then, the recent advances in mitigating the cycling stability issue of high-voltage spinel cathodes are summarized, including the various approaches of structural design, doping, surface coating, and electrolyte modification. Finally, future perspectives and research directions are put forward, aiming at providing insightful information for the development of practical high-voltage spinel cathodes.

Hydroxyapatite Based Materials for Bone Tissue Engineering: A Brief and Comprehensive Introduction

Hydroxyapatite (HA) is widely used in bone tissue engineering for its bioactivity and biocompatibility, and a growing number of researchers are exploring ways to improve the physical properties and biological functions of hydroxyapatite. Up to now, HA has been used as inorganic building blocks for tissue engineering or as nanofillers to blend with polymers, furthermore, various methods such as ion doping or surface modification have been also reported to prepare functionalized HA. In this review, we try to give a brief and comprehensive introduction about HA-based materials, including ion-doped HA, HA/polymer composites and surface modified HA and their applications in bone tissue engineering. In addition, the prospective of HA is also discussed. This review may be helpful for researchers to get a general understanding about the development of hydroxyapatite based materials.

An overview of modification strategies to improve LiNi0·8Co0·1Mn0·1O2 (NCM811) cathode performance for automotive lithium-ion batteries

High nickel LiNi 0 · 8 Co 0 · 1 Mn 0 · 1 O 2 (NCM811) cathode materials have advantages of high specific energy and relatively low-cost, so that it has a very broad application prospect in the future power lithium ion batteries. In this paper, the issues and challenges of NCM811 materials are overviewed, including the disadvantages of mixed cation discharge, weak thermal stability, poor cycle performance and storage characteristics, and safety hazard. The modification strategies for NCM811 materials, including ion doping modification, coating modification, structure design optimization are summarized and analyzed with emphasis on the future development trend and perspectives of high nickel NCM811 materials. • Issues of NCM811 include cation mixing, poor stability and safety, weak cycle and storage. • The modification progress of NCM811 including element doping, coating and other aspects. • The future development direction of NCM811 materials was prospected.

Enhanced energy harvesting ability of polydimethylsiloxane-BaTiO3-based flexible piezoelectric nanogenerator for tactile imitation application

The development of wearable piezoelectric nanogenerator (PENG) has recently drawn extensive attention, especially in selecting lead-free piezoelectric materials with high piezoelectric coefficients. Barium Titanate (BTO) is a kind of environment-friendly piezoelectric ceramics. PENGs derived from BTO based piezo-fillers have recently attracted broad concern. However, the exploration of flexible electrodes and the application of wearable PENGs functioned with imitating tactile have usually been ignored in the pursuit of high output performance. Herein, The porous piezoelectric fillers composed of 0.82Ba(Ti0.89Sn0.11)O3-0.18(Ba0.7Ca0.3)TiO3 are prepared by a freeze-drying method, and then the polydimethylsiloxane (PDMS) is filled into the micropores of the piezoelectric ceramics, forming a distinctive 3D interconnected structure with evenly distributed inorganic piezoelectric materials. Both doping and structure modification can boost the output performance of the BTO-based PENG, from which the rational doping plays a major role in enhancing the electrical output in the current PENG system. To realize fully flexible piezoelectric nanogenerator (PENG), sliver nanowires network integrated with PDMS is adopted as the flexible electrodes, which was fabricated by the techniques combining vacuum filtration with subsequent dry transfer process. The PENG can deliver a maximum open-circuit voltage (VOC) of 39 V and short-circuit (ISC) current of 2.9 μA under a vertical force of 35 N at 2 Hz, with the maximum instantaneous power of 24.2 μW. Moreover, the device can effectively exhibit electric output signal whenever subjected to external pressing or bending stress. The output performance of the PENG at via vertical pressing stress is higher than that bending stress, which is also confirmed by COMSOL simulation. The PENG can not only be employed to harvest biomechanical energy such as digital joints movement, but also display a potential for a tactile perception. This work has established a deep association between lead-free ceramic and wearable imitated touch reception sensors by virtue of flexible PENG, which will paint a magnificent picture for flexible electronics.

Recent advances of biomass carbon dots on syntheses, characterization, luminescence mechanism, and sensing applications

AbstractCarbon dots have attracted much attention due to their high fluorescence intensity, easy modification, good stability, and biocompatibility. However, the realization of low‐cost mass production of high‐quality carbon dots still faces great challenges. Biomass is of non‐toxic and environmentally friendly organism, but a lot of biomass is treated as waste for burning and landfill at present, causing irreparable pollution to the environment. In fact, many biomass resources are ideal candidates for preparing carbon dots. This review focuses on carbon dots including carbon quantum dots (CQDs) and graphene quantum dots (GQDs) which using biomass as carbon source on the aspects of plants and their derivatives, animals and their derivatives and municipal waste. The characterization of the structure and composition of biomass carbon dots, the regulation of fluorescence color and the methods of improving quantum yield (QY) including heteroatom doping and surface modification are introduced in detail. Moreover, biomass carbon dots for detecting metal ions and non‐metal molecules and their quenching mechanism are emphatically introduced in addition to summarizing the luminescence mechanism, and some promising prospects and challenges in this uplifting field are discussed.

Superior electrochemical properties of Zirconium and Fluorine co‐doped Li1.20[Mn0.54Ni0.13Co0.13]O2 as cathode material for lithium ion batteries

In the paper, the Zr4+ and F− co-doping was employed to expectedly improve the rate performance and structure stability of Li1.20[Mn0.54Ni0.13Co0.13]O2. The effects of Zr4+ doping and F− doping on the micro-structure, cathode morphology and element chemical state were investigated by XRD, Rietveld refined XRD, SEM, TEM, and XPS. It indicated the Zr4+ and F− were inserted into the cathode crystal structure with ideally designed. Besides, the electrochemical characterization confirmed that the cathode after the Zr4+ or/and F− doping delivered the superior electrochemical properties when compared to the pristine one. Firstly, the Li1.20[Mn0.52Ni0.13Co0.13Zr0.02]O1.95F0.05 could express a high discharge capacity of 132.6 mAhg−1 at 5C rate, which was 40.1 mAhg−1 larger than that of the pristine one (92.5 mAhg−1). In addition, the Li1.20[Mn0.52Ni0.13Co0.13Zr0.02]O1.95F0.05 remained a capacity retention of 90.7% after 100 cycles at 2C rate and with the 148.2 mAh g−1 left. While the bare cathode delivered an initial discharge capacity of 134.1 mAhg−1 at 2C rate, then dramatically attenuated to 108.7 mAhg−1 after 100 cycles with the capacity retention of 81.1%. The enhanced electrochemical properties of Li1.20[Mn0.52Ni0.13Co0.13Zr0.02]O1.95F0.05 was mainly put down to the suppression of charge transfer resistance increase by the Zr4+ and F− doping modification along with cycles.

Research Progresses on Ceramic Materials of Thermal Barrier Coatings on Gas Turbine

Thermal barrier coatings (TBCs) play a vitally important role in protecting the hot parts of a gas turbine from high temperature and corrosion effectively. More and more attention has been paid to the performance modification of ZrO2-based ceramics and seeking for new ceramic materials to meet requirements of gas turbine TBCs. The working principle, merits, and demerits of main technologies for coating preparation are elaborated in this paper, and the properties of new ceramic materials are reviewed. It is found that the thermal conductivity, thermal stability, mechanical properties, and other performances of traditional ZrO2-based ceramics could be improved effectively by doping modification. The emphases for new ceramic materials research were put on pyrochlores, magnetoplumbites, rare-earth tantalates, etc. Rare-earth tantalates with great potentials as new top ceramic materials were described in detail. In the end, the development directions of advanced top ceramic coatings, combining doping modification with preparation technology to regulate and control structure property of high-performance ceramic material, were put forward.