Polyborosilazane derived ceramics - Nitrogen sulfur dual doped graphene nanocomposite anode for enhanced lithium ion batteries

1D and 2D Boron Nitride Nano Structures: A Critical Analysis for Emerging Applications in the Field of Nanocomposites

Boron nitride (BN) with its 1D and 2D nano derivatives have gained immense popularity in both the field of research and applications. These nano derivatives have proved to be one of the most promising fillers which can be incorporated in polymers to form nanocomposites with excellent properties. These materials have been around for 25 years whereas significant research has been done in this field for only the past decade. There are many interesting properties which are imparted to the nanocomposites wherein thermal stability, large energy band gap, resistance to oxidation, excellent thermal conductivity, chemical inertness, and exceptional mechanical properties are just a few worthy of mention. Hexagonal boron nitride (h-BN) was selected as the parent material by most researchers reviewed in this paper through which 2D derivative Boron nitride nanosheets (BNNS) and 1D derivative Boron nitride nanotubes (BNNTs) are synthesized. This review will focus on the in-depth properties of h-BN and further will concisely focus on BNNS and BNNTs for their various properties. A detailed discussion of the addition of BNNS and BNNTs into polymers to form nanocomposites, their synthesis, properties, and applications is followed by a summary determining the most suitable synthesizing processes and the materials, keeping in mind the current challenges.

Effect of Graphene on the Performance of Silicon-Carbon Composite Anode Materials for Lithium-Ion Batteries

(Si/graphite)@C and (Si/graphite/graphene)@C were synthesized by coating asphalt-cracked carbon on the surface of a Si-based precursor by spray drying, followed by heat treatment at 1000 °C under vacuum for 2h. The impact of graphene on the performance of silicon-carbon composite-based anode materials for lithium-ion batteries (LIBs) was investigated. Transmission electron microscopy (TEM) and selected area electron diffraction (SAED) images of (Si/graphite/graphene)@C showed that the nano-Si and graphene particles were dispersed on the surface of graphite, and thermogravimetric analysis (TGA) curves indicated that the content of silicon in the (Si/graphite/graphene)@C was 18.91%. More bituminous cracking carbon formed on the surface of the (Si/graphite/graphene)@C due to the large specific surface area of graphene. (Si/Graphite/Graphene)@C delivered first discharge and charge capacities of 860.4 and 782.1 mAh/g, respectively, initial coulombic efficiency (ICE) of 90.9%, and capacity retention of 74.5% after 200 cycles. The addition of graphene effectively improved the cycling performance of the Si-based anode materials, which can be attributed to the reduction of electrochemical polarization due to the good structural stability and high conductivity of graphene.

Heteroatom Codoped Graphene: The Importance of Nitrogen

Although graphene has exceptional properties, they are not enough to solve the extensive list of pressing world problems. The substitutional doping of graphene using heteroatoms is one of the preferred methods to adjust the physicochemical properties of graphene. Much effort has been made to dope graphene using a single dopant. However, in recent years, substantial efforts have been made to dope graphene using two or more dopants. This review summarizes all the hard work done to synthesize, characterize, and develop new technologies using codoped, tridoped, and quaternary doped graphene. First, I discuss a simple question that has a complicated answer: When can an atom be considered a dopant? Then, I briefly discuss the single atom doped graphene as a starting point for this review's primary objective: codoped or dual-doped graphene. I extend the discussion to include tridoped and quaternary doped graphene. I review most of the systems that have been synthesized or studied theoretically and the areas in which they have been used to develop new technologies. Finally, I discuss the challenges and prospects that will shape the future of this fascinating field. It will be shown that most of the graphene systems that have been reported involve the use of nitrogen, and much effort is needed to develop codoped graphene systems that do not rely on the stabilizing effects of nitrogen. I expect that this review will contribute to introducing more researchers to this fascinating field and enlarge the list of codoped graphene systems that have been synthesized.

Recent advances in precursor-derived ceramics integrated with two-dimensional materials

This review focused on the recent advances in precursor-derived ceramics integrated with two-dimensional materials. Their fabrication methods, structures and applications were discussed in detail and the perspectives in this field were presented.

Recent advances in heterostructured cathodic electrocatalysts for non-aqueous Li–O2 batteries

Developing efficient energy storage and conversion applications is vital to address fossil energy depletion and global warming. Li–O₂ batteries are one of the most promising devices because of their ultra-high energy density. To overcome their practical difficulties including low specific capacities, high overpotentials, limited rate capability and poor cycle stability, an intensive search for highly efficient electrocatalysts has been performed. Recently, it has been reported that heterostructured catalysts exhibit significantly enhanced activities toward the oxygen reduction reaction and oxygen evolution reaction, and their excellent performance is not only related to the catalyst materials themselves but also the special hetero-interfaces. Herein, an overview focused on the electrocatalytic functions of heterostructured catalysts for non-aqueous Li–O₂ batteries is presented by summarizing recent research progress. Reduction mechanisms of Li–O₂ batteries are first introduced, followed by a detailed discussion on the typical performance enhancement mechanisms of the heterostructured catalysts with different phases and heterointerfaces, and the various heterostructured catalysts applied in Li–O₂ batteries are also intensively discussed. Finally, the existing problems and development perspectives on the heterostructure applications are presented.

The structure–function relationships between heterostructures and their catalytic properties were discussed in detail, and the challenges and improvement strategies for heterostructure based cathodes towards Li–O₂ catalysis were also summarized.

MnCo2 S4 -CoS1.097 Heterostructure Nanotubes as High Efficiency Cathode Catalysts for Stable and Long-Life Lithium-Oxygen Batteries Under High Current Conditions

Constructing the heterostructures is considered to be one of the most effective methods to improve the poor electrical conductivity and insufficient electrocatalytic properties of metal sulfide catalysts. In this work, MnCo2 S4 -CoS1.097 nanotubes are successfully prepared via a reflux- hydrothermal process. This novel cathode catalyst delivers high discharge/charge specific capacities of 21 765/21 746 mAh g-1 at 200 mA g-1 and good rate capability. In addition, a favorable cycling stability with a fixed specific capacity of 1000 mAh g-1 at high current density of 1000 mA g-1 (167 cycles) and 2000 mA g-1 (57 cycles) are delivered. It is proposed that fast transmission of ions and electrons accelerated by the built-in electric field, multiple active sites from the heterostructure, and nanotube architecture with large specific surface area are responsible for the superior electrochemical performance. To some extent, the rational design of this heterostructured metal sulfide catalyst provides guidance for the development of the stable and efficient cathode catalysts for Li-O2 batteries that can be employed under high current conditions.

First-Principles Study of Au-Doped InN Monolayer as Adsorbent and Gas Sensing Material for SF6 Decomposed Species

As an insulating medium, sulfur hexafluoride (SF₆) is extensively applied to electrical insulation equipment to ensure its normal operation. However, both partial discharge and overheating may cause SF₆ to decompose, and then the insulation strength of electrical equipment will be reduced. The adsorption properties and sensing mechanisms of four SF₆ decomposed components (HF, SO₂, SOF₂ and SO₂F₂) upon an Au-modified InN (Au-InN) monolayer were studied in this work based on first-principles theory. Meanwhile, the adsorption energy (E_ad), charge transfer (Q_T), deformation charge density (DCD), density of states (DOS), frontier molecular orbital and recovery property were calculated. It can be observed that the structures of the SO₂, SOF₂ and SO₂F₂ molecules changed significantly after being adsorbed. Meanwhile, the E_ad and Q_T of these three adsorption systems are relatively large, while that of the HF adsorption system is the opposite. These phenomena indicate that Au-InN monolayer has strong adsorption capacity for SO₂, SOF₂ and SO₂F₂, and the adsorption can be identified as chemisorption. In addition, through the analysis of frontier molecular orbital, it is found that the conductivity of Au-InN changed significantly after adsorbing SO₂, SOF₂ and SO₂F₂. Combined with the analysis of the recovery properties, since the recovery time of SO₂ and SO₂F₂ removal from Au-InN monolayer is still very long at 418 K, Au-InN is more suitable as a scavenger for these two gases rather than as a gas sensor. Since the recovery time of the SOF₂ adsorption system is short at 418 K, and the conductivity of the system before and after adsorption changes significantly, Au-InN is an ideal SOF₂ gas-sensing material. These results show that Au-InN has broad application prospects as an SO₂, SOF₂ and SO₂F₂ scavenger and as a resistive SOF₂ sensor, which is of extraordinary meaning to ensure the safe operation of power systems. Our calculations can offer a theoretical basis for further exploration of gas adsorbent and resistive sensors prepared by Au-InN.

Preparation of Bamboo-Like Carbon Nanotube Loaded Piezoresistive Polyurethane-Silicone Rubber Composite

In this study, a novel technology is reported to prepare a piezoresistive polyurethane-silicone rubber nanocomposite. Polyurethane (PU) foam was loaded with a nitrogen-doped bamboo-shaped carbon nanotube (N-BCNT) by using dip-coating, and then, impregnated with silicone rubber. PU was used as a supporting substrate for N-BCNT, while silicone rubber was applied to fill the pores of the foam to improve recoverability, compressive strength, and durability. The composite displays good electrical conductivity, short response time, and excellent repeatability. The resistance was reduced when the amount of N-BCNT (0.43 wt %) was increased due to the expanded conductive path for electron transport. The piezoresistive composite has been successfully tested in many applications, such as human monitoring and finger touch detection.

Applications of Ceramic/Graphene Composites and Hybrids

Research activity on ceramic/graphene composites and hybrids has increased dramatically in the last decade. In this review, we provide an overview of recent contributions involving ceramics, graphene, and graphene-related materials (GRM, i.e., graphene oxide, reduced graphene oxide, and graphene nanoplatelets) with a primary focus on applications. We have adopted a broad scope of the term ceramics, therefore including some applications of GRM with certain metal oxides and cement-based matrices in the review. Applications of ceramic/graphene hybrids and composites cover many different areas, in particular, energy production and storage (batteries, supercapacitors, solar and fuel cells), energy harvesting, sensors and biosensors, electromagnetic interference shielding, biomaterials, thermal management (heat dissipation and heat conduction functions), engineering components, catalysts, etc. A section on ceramic/GRM composites processed by additive manufacturing methods is included due to their industrial potential and waste reduction capability. All these applications of ceramic/graphene composites and hybrids are listed and mentioned in the present review, ending with the authors' outlook of those that seem most promising, based on the research efforts carried out in this field.

Polymer-Derived Ceramic Nanoparticle/Edge-Functionalized Graphene Oxide Composites for Lithium-Ion Storage

Polymer-derived ceramics demonstrate great potential as lithium-ion battery anode materials with good cycling stability and large capacity. SiCNO ceramic nanoparticles are produced by the pyrolysis of polysilazane nanoparticles that are synthesized via an oil-in-oil emulsion crosslinking and used as anode materials. The SiCNO nanoparticles have an average particle size of around 9 nm and contain graphitic carbon and Si₃N₄ and SiO₂ domains. Composite anodes are produced by mixing different concentrations of SiCNO nanoparticles, edge-functionalized graphene oxide, polyvinylidenefluoride, and carbon black Super P. The electrochemical behavior of the anode is investigated to evaluate the Li-ion storage performance of the composite anode and understand the mechanism of Li-ion storage. The lithiation of SiCNO is observed at ∼0.385 V versus Li/Li⁺. The anode has a large capacity of 705 mA h g^-1 after 350 cycles at a current density of 0.1 A g^-1 and shows an excellent cyclic stability with a capacity decay of 0.049 mA h g^-1 (0.0097%) per cycle. SiCNO nanoparticles provide a large specific area that is beneficial to Li⁺ storage and cyclic stability. In situ transmission electron microscopy analysis demonstrates that the SiCNO nanoparticles exhibit extraordinary structural stability with 9.36% linear expansion in the lithiation process. The X-ray diffraction and X-ray photoelectron spectroscopy investigation of the working electrode before and after cycling suggests that Li⁺ was stored through two pathways in SiCNO lithiation: (a) Li-ion intercalation of graphitic carbon in free carbon domains and (b) lithiation of the SiO₂ and Si₃N₄ domains through a two-stage process.

SiOC functionalization of MoS2 as a means to improve stability as sodium-ion battery anode

The development of feasible, scalable, and environmentally-safe electrode materials that provide stable cycling performance are critical for success of beyond lithium rechargeable batteries and supercapacitors. With respect to the sodium-ion battery (SIB) anodes constituting of transition metal dichalcogenides such as molybdenum disulfide (MoS₂), poor cycle stability and fast capacity degradation, due to low electronic conductivity and dissolution of chemical species in the electrolyte, hinders use of these promising layered materials as SIB anodes. Herein we report chemical functionalization in MoS₂ nanosheets with polymer-derived silicon oxycarbide or SiOC with the aim to preserve MoS₂ from dissolution in the SIB organic electrolyte, without compromising its role in sodiation and desodiation processes. Our results suggest that a MoS₂-SiOC composite electrode is effective in bringing improved cycle stability to sodium-ion cycling over neat MoS₂ even after 100 cycles.

Facile One-Pot Solvothermal Synthesis of the RGO/MWCNT/Fe3O4 Hybrids for Microwave Absorption

How to effectively regulate the electromagnetic parameters of magnetic composites to achieve better microwave absorption (MA) performances is still a serious challenge. Herein, we constructed nanocomposites composed of magnetic constituents and carbon materials to obtain high-efficiency electromagnetic wave absorbers. Self-assembled, multi-interfacial, and porous RGO/MWCNT/Fe₃O₄ hybrids (GMFs) were synthesized via in situ one-pot solvothermal method. The growth mechanism of the GMFs would be that the defects on reduced graphene oxide (RGO) provide sites for the crystallization of Fe₃O₄. Also, the RGO and Fe₃O₄ were further linked by the cross-connection of multiwalled carbon nanotubes (MWCNTs), which acted as a bridge. The MA mechanism of GMFs was studied while considering the synergistic effects between the three components (RGO, MWCNT, and raspberry-shaped Fe₃O₄) and their multi-interfacial and porous structure. Also, the MA performance of the GMFs was conducted. The GMFs exhibited a maximum reflection loss (RL) value of -61.29 dB at 10.48 GHz with a thickness of 2.6 mm when the contents of RGO and MWCNT were 6.3 and 1.3 wt %, respectively. The RL values (≤-10 dB) were observed to be in the range of 8.96-12.32 GHz, and the effective microwave absorption bandwidth was tunable from 3.52 to 18 GHz by changing the sample thickness. The results revealed that the multi-interfacial and porous structure of the GMFs is beneficial to MA performance by inducing multiscatterings. Since no toxic solvents were used, this method is environmentally friendly and has potential for large-scale production. The prepared GMFs may have a wide range of applications in MA materials against electromagnetic interference pollution.

Design and characterization of a biomass template/SnO2 nanocomposite for enhanced adsorption of 2,4-dichlorophenol

2,4-Dichlorophenol (2,4-DCP) is a hazardous chlorinated organic chemical derived from phenol that exerts serious effects on living organisms. In the present study, SnO₂ templated with grapefruit peel carbon as a nanocomposite (SnO₂@GPC) was designed via ball-milling, and its mechanism of 2,4-DCP adsorption in aqueous solution was determined. Batch adsorption experiments revealed that the maximum adsorption efficiency of SnO₂@GPC occurred at 6.0 pH, 3 mg L^-1 initial adsorbate concentration, 2 h contact time, and 293 K temperature. The SnO₂@GPC nanocomposite and its non-tin-bearing counterpart, grapefruit derived char (@GPC), showed maximum adsorption capacities (Q_L) of 45.95 and 22.09 mg g^-1 and partition coefficients of 41.77 and 10.83 mg g^-1 μM^-1, respectively. The adsorption of 2,4-DCP was best described by the Redlich-Peterson model followed by the Langmuir model with high correlation coefficients (R² ≥ 0.96), and the adsorption kinetic data best fitted the pseudo-second-order model (R² ≥ 0.98). The thermodynamic parameters indicated that the reaction was spontaneous, exothermic, and involved high affinity between SnO₂@GPC and 2,4-DCP. The high desorption efficiency obtained (>80%) demonstrated the recyclability of the adsorbent. The enhanced Q_L of SnO₂@GPC was due to the effective combination of GPC and SnO₂. A thin porous layer of GPC on SnO₂ nanoparticles provided effective channels, a large surface area, and an abundance of active sites for 2,4-DCP adsorption. Thus, the SnO₂@GPC nanocomposite could potentially be used as a low-cost adsorbent to remove 2,4-DCP from water.

Advances in Template Prepared Nano-Oxides and their Applications: Polluted Water Treatment, Energy, Sensing and Biomedical Drug Delivery

The nano-oxide materials with special structures prepared by template methods have a good dispersion, regular structures and high specific surface areas. Therefore, in some areas, improved properties are observed than conventional bulk oxide materials. For example, in the treatment of dye wastewater, the treatment efficiency of adsorbents and catalytic materials prepared by template method was about 30 % or even higher than that of conventional samples. This review mainly focuses on the progress of inorganic, organic and biological templates in the preparation of micro- and nano- oxide materials with special morphologies, and the roles of the prepared materials as adsorbents and photocatalysts in dye wastewater treatment. The characteristics and advantages of inorganic, organic and biological template are also summarized. In addition, the applications of template method prepared oxides in the field of sensors, drug carrier, energy materials and other fields are briefly discussed with detailed examples.

Superior electrochemical performance of a novel LiFePO4/C/CNTs composite for aqueous rechargeable lithium-ion batteries

Olivine LiFePO₄ covered flocculent carbon layers wrapped with carbon nanotubes (CNTs) prepared by sol-gel method and calcination is used as the cathode material for aqueous rechargeable lithium-ion batteries (ARLBs). The phase structures and morphologies of the composite material are characterized by X-ray diffraction (XRD), selected area electron diffraction (SAED), and transmission electron microscopy (TEM). The mechanism and method through which CNTs and flocculent carbon improve the electrochemical performance are investigated in an aqueous lithium-ion battery by setting up a comparative experiment. The ARLB system is assembled using a LiFePO₄/C/CNTs cathode and a zinc anode in 1 mol L^-1 ZnSO₄·7H₂O and saturated LiNO₃ aqueous solution (pH = 6), which can deliver a capacity of 158 mA h g^-1 at a rate of 1C. Even at a rate of 50C, it still has a capacity of 110 mA h g^-1 after 250 cycles with fantastic capacity retention (95.7%). The lithium-ion diffusion coefficient increases by an order of magnitude due to the addition of CNTs together with flocculent carbon. Four LEDs are successfully powered by the ARLBs for more than one minute to demonstrate the practical application. The excellent rate capabilities and thrilling discharge capacity at a high rate indicate that this cathode material possesses excellent electrochemical performance, and this ARLB system exhibits excellent potential as a power source for environmental applications.

A highly Li+-conductive HfNb24O62 anode material for superior Li+ storage

Highly Li⁺-conductive HfNb₂₄O₆₂ is explored as a new intercalation-type anode material for fast-charging, large-capacity, safe and durable Li⁺ storage.

Improved electrochemical performance of 2D accordion-like MnV2O6 nanosheets as anode materials for Li-ion batteries

MnV₂O₆ is a promising anode material for lithium ion batteries with high theoretical specific capacity, abundant reserves and inexpensive constituent elements.

Porous CuO@C composite as high-performance anode materials for lithium-ion batteries

The in situ formation of a carbon matrix can confine the growth of CuO nanoparticles, which can provide more exposed active sites for electrochemical reactions.

Interpenetrating graphene network bct-C40: a promising anode material for Li ion batteries

The stable sp²-C atoms in graphite enable its excellent structural and electrochemical stability as an anode material for Li-ion battery applications, while the limited Li-storage capacity of graphite also originates from the sp² hybridization. Herein, from first-principles calculations, we show that a synergistic effect of sp² and sp³ hybridized C atoms can substantially enhance the Li-storage performance in carbon-based anodes, using bct-C₄₀ as an example, which is constructed with interconnected graphene layers (sp² hybridized C atoms) and the connecting points are composed of sp³-C atoms. Charge transfer from sp²-C atoms to sp³-C atoms has been found, leading to unoccupied electronic states forming around the Fermi level. Furthermore, we found that the unoccupied electronic states are contributed by the p_z orbital of the sp²-C atoms, resulting in stronger interactions between C atoms and intercalated Li atoms. As a result, the Li intercalation concentration in bct-C₄₀ can reach as high as LiC_2.5 (corresponding to a capacity of 893 mA h g^-1), much higher than that of LiC₆ in graphite (372 mA h g^-1). Furthermore, bct-C₄₀ inherits good structural and electrochemical stability, a metallic electronic structure, and low Li-ion migration energy barriers (0.067-0.112 eV) from the sp² hybridized graphene structures, therefore very good Li-storage performance is expected, indicating that bct-C₄₀ can be used as a high-performance anode material for lithium ion batteries. Our study provides new insights into the functionality of sp²- and sp³-C atoms in carbon-based anode materials and is helpful for the designing of new carbon-based anodes.

Tungsten oxide nanostructures and nanocomposites for photoelectrochemical water splitting

Hydrogen production from photoelectrochemical (PEC) water splitting using semiconductor photocatalysts has attracted great attention to realize clean and renewable energy from solar energy. The visible light response of WO3 with a long hole diffusion length (∼150 nm) and good electron mobility (∼12 cm2 V-1 s-1) makes it suitable as the photoanode. However, WO3 suffers from issues including rapid recombination of photoexcited electron-hole pairs, photo-corrosion during the photocatalytic process due to the formation of peroxo-species, sluggish kinetics of photogenerated holes, and slow charge transfer at the semiconductor/electrolyte interface. This work highlights the approaches to overcome these drawbacks of WO3 photoanodes, including: (i) the manipulation of nanostructured WO3 photoanodes to decrease the nanoparticle size to promote hole migration to the WO3/electrolyte interface which benefits the charge separation; (ii) doping or introducing oxygen vacancies to improve electrical conductivity; exposing high energy crystal surfaces to promote the consumption of photogenerated holes on the high-active crystal face, thereby suppressing the recombination of photogenerated electrons and holes; (iii) decorating with co-catalysts to reduce the overpotential which inhibits the formation of peroxo-species; (iv) other methods such as coupling with narrow band semiconductors to accelerate the charge separation and controlling the crystal phase via annealing to reduce defects. These approaches are reviewed with detailed examples.

Fabrication of regular macro-mesoporous reduced graphene aerogel beads with ultra-high mechanical property for efficient bilirubin adsorption

Three-dimensional graphene materials have been widely studied in many fields for their role as potential absorbent, especially for bilirubin adsorption. In this study, we developed a simple method to prepare reduced graphene aerogel beads as hemoperfusion materials for fast bilirubin adsorption. The graphene oxide (GO) aerogel beads were produced by self-assembly of GO nanosheet that cross-linked by Ca²⁺ previously in a coagulation bath, then it was reduced by ascorbic acid and lyophilized to yield the reduced graphene aerogel beads. The beads had a regular macroscopic spherical structure with a diameter of about 1.3-2 mm, where the macroporosity was about 10 μm and the mesoporosity was about 12 nm. The macro-mesoporous structure also gave the reduced graphene aerogel beads ultra-high mechanical strengths and high specific surface area, which were both important for hemoperfusion materials. Moreover, the fixed-bed column adsorption revealed that the reduced graphene aerogel beads manifested excellent bilirubin adsorption (649.512 mg/g) with a rapid adsorption equilibrium time (1.5 h) under the optimized conditions. Even in the bilirubin-enriched blood, the adsorption capacity of the beads could reach 367.14 mg/g. Furthermore, the aerogel beads had a low hemolysis ratio and improved anticoagulant property showing good blood compatibility. Hence, the spherical reduced graphene aerogel beads with millimeter-level size presented a good potential for clinical applications in hemoperfusion therapy.

Facile Synthesis of Novel V0.13Mo0.87O2.935 Nanowires With High-Rate Supercapacitive Performance

Binary metal oxides composed of molybdenum–vanadium oxides are promising candidates for supercapacitors. Here, we report the synthesis of one-dimensional V_0.13Mo_0.87O_2.935 nanowires through a facile one-step hydrothermal method. This nanowire presented a high specific capacitance of 394.6 F g⁻¹ (1 mV s⁻¹) as an electrode applied to the supercapacitor. Importantly, this electrode showed a perfect rate capability of 91.5% (2 to 10 A g⁻¹) and a continuous verified outstanding cyclic voltammetry of 97.6% after 10,000 cycles. These superior electrochemical properties make the synthesized V_0.13Mo_0.87O_2.935 nanowires a prospective candidate for high-performance supercapacitors.

2D MXenes as Co-catalysts in Photocatalysis: Synthetic Methods

Since their seminal discovery in 2011, two-dimensional (2D) transition metal carbides/nitrides known as MXenes, that constitute a large family of 2D materials, have been targeted toward various applications due to their outstanding electronic properties. MXenes functioning as co-catalyst in combination with certain photocatalysts have been applied in photocatalytic systems to enhance photogenerated charge separation, suppress rapid charge recombination, and convert solar energy into chemical energy or use it in the degradation of organic compounds. The photocatalytic performance greatly depends on the composition and morphology of the photocatalyst, which, in turn, are determined by the method of preparation used. Here, we review the four different synthesis methods (mechanical mixing, self-assembly, in situ decoration, and oxidation) reported for MXenes in view of their application as co-catalyst in photocatalysis. In addition, the working mechanism for MXenes application in photocatalysis is discussed and an outlook for future research is also provided.

Assessing young consumers' awareness and participation in sustainable e-waste management practices: a survey study in Northwest China

The massive generation of electronic waste (e-waste) and the informal recycling of e-waste are serious concerns in China. As a hazardous waste stream, e-waste calls for sustainable management practices to avoid adverse effects on environment and health. However, consumers' awareness and active participation are needed to make e-waste management successful. Therefore, this study is an exploratory attempt to investigate young consumer awareness, knowledge, and participation in sustainable e-waste management practices. Meanwhile, the study reviews the current situation of e-waste recycling, its related legislative framework, and practices in China. The survey revealed that the respondents have keen environmental consciousness, while they have low awareness about e-waste-related rules and regulations, recycling programs, and the formal and informal recycling sector. The findings provide valuable insights for practitioners in order to promote environmental awareness and sustainable e-waste management practices among young consumers in China.

Dissipative Particle Dynamics Simulations of a Protein-Directed Self-Assembly of Nanoparticles

Design and fabrication of multifunctional porous structures play key roles in the development of high-performance energy storage devices. Our experiments demonstrated that nanostructured porous components, such as electrodes and interlayers, generated from the protein-directed self-assembly of nanoparticles can significantly improve the battery performances. The protein-directed assembly of nanoparticles in solution is a complex process involving the complicated interactions among proteins, particles, and solvent molecules. In this paper, we investigate the effects of coating proteins and specific solvent environments on the assembled porous structures. Comprehensive dissipative particle dynamics (DPD) simulations have been implemented to explore the molecular interactions and uncover the fundamental mechanisms in a gelatin-directed self-assembly of carbon black particles under different solvent conditions. Our simulations show that compact triple-strand "rod-like" structures are formed in water while loose curved "sheet-like" structures are formed in an acetic acid/water mixture. The structural difference is mainly due to the redistribution of the charges on the gelatin side chains under specific acid-solvent conditions. The strong and flexible "sheet-like" structures lead to a homogenous porous structure with high porosity and with large functionalized surfaces. Our simulations results can reasonably explain the experimental observations; this work demonstrates the great potential of DPD as a powerful tool in guiding future experimental design and optimization.

Recycling valuable metals from spent lithium-ion batteries by ammonium sulfite-reduction ammonia leaching

The cathode powder is obtained by wet crushing and screening, and the leaching behavior of Li, Ni, Co, Cu, and Al is then investigated using a ternary leaching system composed of ammonia, ammonium sulfite, and ammonium bicarbonate. Ammonium sulfite is necessary as a reductant to improve the Li, Ni, and Co leaching efficiencies, and ammonium bicarbonate acts as a buffer in ammoniacal solutions. A detailed understanding of the selective leaching process is obtained by investigating the effects of parameters such as the leaching reagent composition, leaching time (0-300 min), temperature (40-90 °C), solid-to-liquid ratio (10-50 g/L), and agitation speed (300-700 rpm). It is found that Ni and Cu could be almost fully leached out, while Al is hardly leached and Li(60.53%) and Co(80.99%) exhibit a moderate leaching efficiency. The results show that the optimum solid-liquid ratio of the leaching system is 20 g/L, and the increase of temperature and reaction time is beneficial to metal leaching. The leaching kinetics analysis shows that the chemical reaction control explains the leaching behavior of Li, Ni, and Co well. Therefore, this work may be beneficial for further recycling valuable metals from leaching solutions by introducing an extraction agent.