Interfacial Reaction Mechanism Research Articles

Peroxymonosulfate as inducer driving interfacial electron donation of pollutants over oxygen-rich carbon–nitrogen graphene-like nanosheets for water treatment

Herein, a novel metal-free catalyst consisting of multiporous oxygen-rich carbon–nitrogen graphene-like nanosheets (OLAA-CN NSs) is first developed through a staged temperature-programmed calcination of l-ascorbic acid (LAA)-modified dicyandiamide precursor. It is found that the oxygen species from l-ascorbic acid (OLAA) are introduced into the graphene-like basic matrix and replace partial N atoms to form the COC-R structure, leading to the non-uniform distribution of electrons on the catalyst surface, and the formation of electron-rich centers around the COC microareas according to a series of characterization techniques. As a result, OLAA-CN NSs exhibits excellent performance for refractory pollutant removal in the presence of peroxymonosulfate (PMS) and dissolved oxygen. Some pollutants with complex structures are even completely degraded within only 1 min. The interface reaction mechanism is further revealed that PMS mainly acts as an active inducer to drive the electron donation of pollutants over OLAA-CN NSs. These electrons are finally utilized by dissolved oxygen to generate reactive oxygen species (ROS) through the interface process. This reaction system results in pollutants that can either be cleaved directly by surface oxidation process or degraded by the attack of the generated ROS, such as singlet oxygen (1O2) and superoxide radicals (O2•−), through oxygen activation, which significantly reduces the resource and energy consumption in advanced wastewater treatment by harnessing the energy of pollutants and dissolved oxygen in the water.

Interfacial reaction mechanism between Stellite 6 alloy and CuO

The interfacial reaction of Stellite 6 alloy with CuO at 1200 °C in pure argon was investigated. The bubbling phenomenon was observed during the reaction. The results show that the reaction produced solid oxides (CoO, Cr2O3, SiO2, MnO2 and CoCr2O4/NiCr2O4/Fe3O4) and pure copper, as well as possible CO and CO2 gases. The product gases and oxides caused holes and cracks in the sample.

Research status and prospect of ceramic crucibles for induction melting of titanium alloys

<p indent="0mm">Titanium alloys possess high specific strength, superior heat resistance, excellent corrosion resistance, outstanding physiological compatibility, etc., and thus being considered as the most ideal lightweight structural materials as well as potent biomedical materials. Generally, Ti alloys are manufactured via the technique of ingot metallurgy; however, it suffers from critical issues of high energy consumption and high cost, which desperately need to be well addressed. According to previous research, the crucible vacuum induction melting technology has high superheat and strong electromagnetic stirring, with which titanium alloy ingots with uniform composition can be achieved without applying multiple remelting. The crucible vacuum induction melting not only benefits the removal of low melting point impurities, but also significantly improves the energy consumption efficiency as the forced water cooling becomes not indispensable during the processing. As a result, the crucible vacuum induction melting has been the most potential method to overcome the problems of high energy consumption and low material yield existed in conventional melting technology. However, titanium alloys can react with almost all the refractories because of their high chemical activity, resulting in the pollution of titanium ingot and thus seriously restricting the development and application of this technology in titanium alloy production. For this reason, preparation special crucibles with corrosion resistance to titanium liquid is crucial to realizing low-cost, high-quality, and high-efficiency smelting of titanium alloys. Herein, we provide a comprehensive review of the research status of ceramic crucibles for titanium alloys including the selection of materials (thermodynamic criterion, corrosion resistance mechanism, composition optimization) and the promising processes to improve the durability of these crucibles. Usually, the thermodynamic criterion is used as the first-step to pick ceramic materials with high chemical stability, which involves a comparison of the free energies of formation of ceramic materials with their corresponding titanium compounds. It is necessary to further evaluate the interface reaction mechanism between candidate ceramic materials and titanium melts under induction melting conditions to compensate for the neglect of disregarding physical and chemical erosion in thermodynamic approach. Based on a systematically comparison of the interface reaction mechanism between titanium melts and various common refractory materials involving oxide ceramics (Y₂O₃ and CaO), zirconate ceramics (BaZrO₃ and (Ca,Sr,Ba)ZrO₃) and non-oxide ceramics, AlN and TiN show promising properties for melting titanium alloys due to their relatively smaller oxygen contamination. In addition to corrosion resistance of ceramics against titanium melts, the thermal shock resistance is the other critical criterion to realize a long service life of the crucibles under repeated induction melting conditions. Scholars attempted many methods, such as porosity optimization, doping modification, surface coating, to solve the imbalance between the corrosion resistance of titanium liquid and thermal shock resistance of materials. Currently, the crucibles can only be prepared at laboratory size, how to realize the production of large-size crucibles with balancing the cost, corrosion resistance and thermal shock resistance is full of serious challenges. On the basis of the recent research progress of Huazhong University of Science and Technology, innovative thinking in terms of the future development of ceramic crucibles for titanium alloy induction melting is suggested: (1) the optimization of refractories: how to reap the advantages of computer technology to speed up the development of new crucible materials; (2) higher demands for thermal shock resistance and high temperature strength: figuring out the relationship between the preparation parameters and the surface quality of the crucibles; (3) the preparation of the special crucibles with large size, high durability: addition of ultra-high temperature reinforcements being a promising route for the fabrication of industrial grade crucibles for titanium alloys induction melting.

Partial transient liquid phase diffusion bonding of ZrC-SiC and 304 stainless steel by Ti/Ni interlayer: Microstructure and properties

The ZrC-SiC ceramic (ZS) was joined to 304 stainless steel (304SS) by using Ti/Ni interlayer. The joining process involves a transient liquid phase bonding at the ZS interface and a diffusion bonding at the 304SS interface. It is found TiCx grew fast on ZS interface or precipitated as particles in certain region of transient liquid, and its distribution and morphology were controlled by Ti gradient. Small amount of Si dissolved into liquid and then precipitated as Ti3Ni2Si with similar lattice structure to Ti2Ni. During solid-state diffusion, the TiNi reaction layer quickly transformed to refractory TiNi3 layer with a small number of Kirkendall pores and Ni5Zr phase at the TiNi3/Ni boundary. The underlying mechanism of interfacial reactions and microstructure evolution were proposed. The maximum shear strength of 97 ± 10 MPa was achieved when joining at 960 °C for 3 h. The failure mainly occurred along TiNi3/Ni boundary due to the presence of Kirkendall pores.

Preparation and application evaluation of La2O3-doped Y2O3 crucible materials for melting TiAl alloys

A new La2O3-doped Y2O3 crucible materials was fabricated and evaluated by TiAl alloys melting test. Microstructure and properties of the La2O3-doped Y2O3 ceramics were systemically investigated. In addition, interfacial reaction mechanism of the La2O3-doped Y2O3 crucible materials and TiAl alloys, together with oxygen content of TiAl alloys were discussed. Solid solution of La3+ in the crystal lattice of Y2O3 significantly improved sintering properties of the La2O3-doped Y2O3 crucible materials and decreased the open porosity. Compared with pure Y2O3, when adding 15 wt% La2O3, the open porosity and strength retention ration after thermal shock test of the La2O3-doped Y2O3 crucible materials changed from 10.8% to 3.9% and from 64% to 78%, respectively. The interfacial reaction between La2O3-doped Y2O3 crucible materials and TiAl alloys belongs to physical dissolution, and no reaction products were found during the melting of TiAl alloys. When using the 15 wt% La2O3-doped Y2O3 crucible materials to melt TiAl alloys, oxygen content of the TiAl ingot declined to 530 ppm, which was only one fourth of that using pure Y2O3 materials.

Superior high-temperature tensile properties of aluminum matrix composites reinforced with carbon nanotubes

The relatively low strength of aluminum (Al) alloys and Al matrix composites at high temperatures has greatly limited their applications in aerospace and automobile areas. In this study, high-performance carbon nanotubes (CNTs)/Al composites with high room-temperature tensile strength over 500 MPa were tested at elevated temperatures up to 400 °C. Results showed that the strength of CNTs/Al composites increased with increasing CNT content up to 5 vol%. CNTs/Al composites showed improved reinforcing effects at elevated temperatures compared with those at room temperature. Consequently, the 5 vol%CNTs/Al composite achieved high tensile strength of 205 MPa when tested at 400 °C, which was superior to those values (less than 100 MPa) of most available Al matrix composites. The underlying mechanism was thoroughly discussed from the grain sizes, phase compositions, interface reaction and strengthening mechanisms at different testing temperatures. The results have revealed the excellent high-temperature properties of CNTs/Al composites and their potential use at elevated temperatures.

TiO2 as Second Phase in Na3Zr2Si2PO12 to Suppress Dendrite Growth in Sodium Metal Solid‐State Batteries

AbstractSolid‐state sodium–metal batteries will not achieve reasonable power density without electrolytes that solve the dendrite (filamentation) problem. Metal‐filament formation during plating at ceramic/metal interfaces can cause electrical failure by internal short‐circuit or mechanical failure by electrolyte fracture. Herein, an Na3Zr2Si2PO12 (NZSP) sodium‐ion‐conducting NASICON electrolyte in which TiO2 is incorporated as an additive is presented, leading to a two‐phase composite NZSP(TiO2) with improved density, Young's modulus, hardness, grain structure, and bulk permittivity. These features of NZSP(TiO2) suppress dendrite growth along grain boundaries, microcracks, and micropores. As well as demonstrating ultralow ceramic/Na kinetic resistance with electrochemical measurements, X‐ray photoelectron spectroscopy is performed to probe interfacial reaction mechanisms. The TiO2 phase forms within grain boundaries and along NZSP surfaces. This modifies the two‐phase material's microstructure and improves its electrochemical performance, while also increasing the critical current density for dendrite formation. Design guidelines are discussed to mitigate microscopic defects and dendrites in two‐phase ceramic electrolytes.

How Polytetrafluoroethylene Lubricates Iron: An Atomistic View by Reactive Molecular Dynamics.

The tribochemistry and transfer film formation at the metal/polymer interface plays an essential role in surface protection, wear reduction, and lubrication. Although the topic has been studied for decades, challenges persist in clarifying the nanoscale mechanism and dynamic evolution of tribochemical reactions. To investigate the tribochemistry between iron and polytetrafluoroethylene (PTFE) in ambient and cryogenic environments, we have trained and expanded a ReaxFF reactive force field to describe iron-oxygen-water-PTFE systems (C/H/O/F/Fe). Using ReaxFF molecular dynamics simulations, we find that mechanical shearing of single asperity induced the degradation of PTFE molecules and radicals, showing subsequent oxidation and hydroxylation reactions of the radicals initiated by C-C bond cleavage, in agreement with previous experimental observations. Furthermore, we studied mechanisms of interfacial tribochemical reactions and formation of transfer films. We found that tribochemical wear and Fe-C and Fe-F bonding networks are important mechanisms for anchoring molecular chains to form a transfer film on the iron countersurface. Hydroxyl groups can dehydrogenate to form short and strong chelation bonds with the Fe2O3 countersurface. A friction-induced oriented molecular layer plays a key role in reducing friction, which is responsible for the excellent lubrication property. By varying temperatures in the range of 10-300 K, we found a nonmonotonic change in friction with a maxima at 100 K. At cryogenic temperatures, the molecular mobility was obviously suppressed, while the chain rigidity was enhanced, resulting in the less oriented interface and brittle-like shear interface, which is responsible for nonmonotonic friction. This work elucidates mechanisms of tribochemical reactions and transfer film formation between iron and PTFE at the atomistic level, facilitating design and development of self-lubricating materials, especially under harsh conditions.

On the interface reactions and stability of nonfullerene organic solar cells.

Long-term stability is critical for organic solar cells (OSCs) for practical applications. Several factors affect the stability of OSCs, including materials stability, morphology stability of bulk-heterojunctions and interface stability. In this perspective, we focus on interface stability due to interfacial reactions between the emerging acceptor–donor–acceptor (A–D–A) type nonfullerene active layers and interfacial layers. The description covers the initial phenomena of interfacial instability, mechanism of interfacial reactions, and strategies adopted to suppress interfacial reactions between the nonfullerene active layers and interfacial layers. Methods to test and analyze the chemical instability of nonfullerene acceptors are also included. The C Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> C vinyl linker between the donor moiety and acceptor moiety is chemically or photochemically reactive and is a weak point for interface stability. The interface stability of OSCs could be enhanced by reducing the reactivity of the CC vinyl linker or removing it directly, modifying the surface of interfacial layers, and developing other novel interfacial materials.

Interface Reaction Mechanism During Laser Brazing of Zn–Mg–Al-Coated Steel To Aa 6061 Aluminum Alloy

Interface Reaction Mechanism During Laser Brazing of Zn–Mg–Al-Coated Steel To Aa 6061 Aluminum Alloy

Investigations of interfacial reaction and toughening mechanisms of Ta fiber-reinforced TiAl-matrix composites

Continuous fiber-reinforced TiAl-matrix composites are a potential structural material to satisfy the service requirements in space industry. Ta fiber with outstanding plasticity and toughness is regarded as a promising reinforcement. In this work, a 10 vol% Ta fiber-reinforced TiAl composite was prepared by combining slurry casting and vacuum hot pressing under condition of 1150 °C/ 35 MPa/ 2 h. Microstructure of interfacial reaction zone of the composite was investigated; meanwhile, thermodynamic calculation and theoretical analysis were conducted to explain the formation mechanisms of the reaction products. Three types of reaction products σ-Ta 2 Al, B2 and α 2 phases were formed between Ta fiber and TiAl matrix. σ phase was adjacent to Ta fiber with a fine grain structure, which was formed due to the lowest formation free energy. The aggregation of β stabilizers in Ti-rich region resulted in the formation of B2 phase that was close to σ phase. α 2 phase relied on B2 phase to nucleate and grow based on the Burgers relationship and their structure symmetry. Three-point bending tests show the fracture toughness (K IC ) of the Ta f /TiAl composite was 58% higher than that of pure TiAl matrix. The main toughening mechanism of the Ta f /TiAl composite was plastic deformation of the Ta fiber, meanwhile the interfacial debonding also had a contribution to toughening the TiAl alloy. The interfacial debonding location was mainly at the Ta / L I -σ interface due to the existence of thermal residual stress. • The interfacial reaction products from Ta fiber to TiAl matrix in turn were σ-Ta 2 Al, B2 and α 2 phases. • The fracture toughness (K IC ) of Ta f /TiAl composite has increased by 58% than that of pure TiAl matrix. • Plastic deformation of the Ta fiber was the main toughening mechanisms, and interfacial debonding also had a contribution to toughening TiAl alloy. • Interfacial debonding location was mainly at the Ta/L I -σ interface due to the existence of thermal residual stress.

Interfacial reaction of aluminum borate whisker reinforced Mg-10Gd-3Y-1Zn-0.4Zr (wt%) alloy matrix composite

Magnesium matrix composites usually possess high strength and stiffness as well as low coefficient of thermal expansion, which makes them promising in lightweight and energy-saving strategies. Although the interfacial bonding state has a crucial influence on the properties of magnesium matrix composites, the interfacial reaction mechanism of Mg-RE alloy matrix composites is still unclear. Herein, the interfacial reaction and microstructure of Mg-10Gd-3Y-1Zn-0.4Zr (wt%) alloy matrix composite reinforced with aluminum borate whisker (Al18B4O33w) were reported by heating the matrix to a semisolid region and inducing the interfacial reaction to continue. After heat treatment at 600 °C for 6 h, the thickness of the interface layer increased from 50‐120 nm to about 335 nm, and the main interfacial reaction product was (Mg0.4Al0.6)Al1.8O4. With the increase of heating time to 12 h, a new double interface layer with (Mg0.4Al0.6)Al1.8O4 in the inner layer and MgO in the outer layer was formed. The difference of interfacial reaction products during isothermal heat treatment was related to the concentration gradient of Mg atoms along the radial direction of the whiskers and the hindrance of the migration of Mg atoms by reaction products formed in the early stage. These findings provide a further understanding of the interfacial reaction of Al18B4O33w reinforced Mg-RE alloy matrix composites.

The Gnps Evolution and Interface Reaction Mechanism of Gnps/Ta15 Composites by Pre-Sintering and Canned Hot Extrusion

The Gnps Evolution and Interface Reaction Mechanism of Gnps/Ta15 Composites by Pre-Sintering and Canned Hot Extrusion

Effects of Different Types of Interlayers on the Interfacial Reaction Mechanism at the Cu Side of Al/Cu Lap Joints Obtained by Laser Welding/Brazing.

The influence of tin foil and Ni coatings on microstructures, mechanical properties, and the interfacial reaction mechanism was investigated during laser welding/brazing of Al/Cu lap joints. In the presence of a Zn-based filler, tin foil as well as Ni coating strengthened the Al/Cu joints. The tin foil only slightly influenced the joint strength. It considerably improved the spreading/wetting ability of the weld filler; however, it weakened the bonding between the seam and the Al base metal. The Ni coating considerably strengthened the Al/Cu lap joints; the highest tensile strength was 171 MPa, which was higher by 15.5% than that of a joint without any interlayer. Microstructure analysis revealed that composite layers of Ni3Zn14–(τ2 Zn–Ni–Al ternary phase)–(α-Zn solid solution)–Al3Ni formed at the fusion zone (FZ)/Cu interface. Based on the inferences about the microstructures at the interfaces, thermodynamic results were calculated to analyze the interfacial reaction mechanism. The diffusion of Cu was limited by the Ni coating and the mutual attraction between the Al and Ni atoms. The microstructure comprised Zn, Ni, and Al, and they replaced the brittle Cu–Zn intermetallic compounds, successfully strengthening the bonding of the FZ/Cu interface.

Surface sulfur vacancies enhanced electron transfer over Co-ZnS quantum dots for efficient degradation of plasticizer micropollutants by peroxymonosulfate activation

Peroxymonosulfate (PMS) activation in heterogeneous processes is a promising water treatment technology. Nevertheless, the high energy consumption and low efficiency during the reaction are ineluctable, due to electron cycling rate limitation. Herein, a new strategy is proposed based on a quantum dots (QDs)/PMS system. Co-ZnS QDs are synthesized by a water phase coprecipitation method. The inequivalent lattice-doping of Co for Zn leads to the generation of surface sulfur vacancies (SVs), which modulates the surface of the catalyst to form an electronic nonequilibrium surface. Astonishingly, the plasticizer micropollutants can be completely degraded within only tens of seconds in the Co-ZnS QDs/PMS system due to this type of surface modulation. The interfacial reaction mechanism is revealed that pollutants tend to be adsorbed on the cobalt metal sites as the electron donors, where the internal electrons of pollutants are captured by the metal species and transferred to the surface SVs. Meanwhile, PMS adsorbed on the SVs is reduced to radicals by capturing electrons, achieving effective electron recovery. Dissolved oxygen (DO) molecules are also easily attracted to catalyst defects and are reduced to O 2 •− , further promoting the degradation of pollutants. A new strategy is reported to generate electron-rich/poor reaction sites on the catalyst surface by constructing sulfur vacancies through Co doping into the ZnS QDs lattice. PMS and DO are captured by sulfur vacancies and reduced to reactive oxygen species, thus rapidly degrading organic pollutants.

Carbonized MOF-Coated Zero-Valent Cu Driving an Efficient Dual-Reaction-Center Fenton-like Water Treatment Process through Utilizing Pollutants and Natural Dissolved Oxygen

Excessive consumption of resources and energy is inevitable in a classical Fenton reaction due to the demand for electron donors or electron acceptors (H2O2) and the existence of reaction rate-limiting steps. In this work, we propose an innovative strategy to solve this key scientific problem by utilizing the organic pollutants and the dissolved oxygen (DO) naturally present in the wastewater through a newly developed carbonized metal–organic framework-coated zero-valent Cu catalyst (ZVC@CMOF). It has been found that the formation of a C–O–Cu bond bridge on the catalyst induces electron polarization distribution to form a non-equilibrium surface with electron-rich or electron-poor microareas based on a series of characterization techniques. This typical non-equilibrium surface feature leads to excellent performance for pollutant conversion and a new interfacial reaction mechanism. Various types of refractory organic pollutants can be rapidly degraded in a few minutes in the ZVC@CMOF Fenton-like systems, accompanied by good stability and a wide pH adaptation range. The interfacial reaction processes are revealed by experimental analysis and theoretical calculations, in which pollutants and DO act as electron donors and electron acceptors in the electron-poor and electron-rich microareas, respectively, which greatly reduce the consumption of H2O2 and improve the reaction efficiency and catalytic performance for pollutant removal.

Ab initio -based approach for the oxidation mechanisms at SiO2 /4H-SiC interface: Interplay of dry and wet oxidants during interfacial reaction

Effects of the coexistence of dry and wet oxidants on the reaction process at ${\mathrm{SiO}}_{2}$/4H-SiC(0001) and ($000\overline{1}$) interfaces during SiC oxidation are systematically investigated by performing ab initio calculations. We find characteristic features of the interfacial reaction mechanisms, which are dependent on the plane orientation and wet oxidation condition. The incorporation of wet oxidants leads to lower barrier heights for the reaction of ${\mathrm{O}}_{2}$ molecules, resulting in the promotion of interfacial reaction at the ${\mathrm{SiO}}_{2}$/4H-SiC(0001) interface. In contrast, the coexisting ${\mathrm{O}}_{2}$ molecule assists the reactions by ${\mathrm{H}}_{2}\mathrm{O}$ molecule and OH groups at the ${\mathrm{SiO}}_{2}$/4H-SiC($000\overline{1}$) interface. Furthermore, we estimate the linear rate constants in the Deal-Grove model using the calculated barrier heights and reveal that the preferable wet ambient condition at the ${\mathrm{SiO}}_{2}$/4H-SiC(0001) interface is different from that at the ${\mathrm{SiO}}_{2}$/4H-SiC($000\overline{1}$) interface. The difference in the rate constants is caused by the difference in the rate-limiting reaction pathway between ${\mathrm{SiO}}_{2}$/4H-SiC(0001) and ($000\overline{1}$) interfaces. These calculated results offer better understanding of the atom-scale mechanisms for the significant enhancement of SiC oxidation by the interplay of dry and wet oxidants.

All-Solid-state Lithium Battery with Sulfide Electrolyte: From Interface Design to Full Cell

All-solid-state lithium batteries (ASSLBs) have gained intensive attention because of their intrinsic safety and high energy density.1 However, significant interfacial challenges such as detrimental interfacial reactions, poor solid-solid ionic contact, and lithium dendrite growth have stymied the development of ASSLBs. Besides that, the large gap between fundamental research and practical engineering design has slowed down ASSLBs commercialization. Over the past five years, our group has been dedicated to the research and development of ASSLBs, with the aims of overcoming the interfacial challenges and pushing ASSLBs closer to commercialization. First, we have regulated the interfacial ion and electron transport via increasing the ionic conductivity of interfacial buffer layers,2 manipulating interfacial nanostructures,3, 4 using single-crystal cathodes,5 deciphering interfacial reaction mechanisms,6 and constructing artificial solid electrolyte interphases (SEI).7 Based on these advanced and innovative strategies, the large interfacial resistance was successfully eliminated. As a result, ASSLBs with sulfide electrolytes demonstrated both ultra-long cycling stability and high-rate performance. To transfer these viable technologies into practical application and bridging the large gap between laboratory research and practical full cells, we are committed to engineering solid-state pouch cells with competitive energy density and low cost. Recently, a solvent-free and cost-effective process was developed for fabricating ultra-thin inorganic solid electrolyte membranes as well as solid-state thick electrodes. Furthermore, a solid-liquid interface and a plastic crystal electrolyte were engineered to enable practical solid-state pouch cells with high energy density and excellent safety.8, 9 These works not only provide an in-depth understanding of interfacial mass and charge transport but also offer feasible strategies to commercialize practical solid-state pouch cells. References C. Wang, J. Liang, Y. Zhao, M. Zheng, X. Li, X. Sun*, Energy Environ. Sci. , 2021, doi:10.1039/d1ee00551k.C. Wang, J. Liang, S. Hwang, X. Li, Y. Zhao, K. Adair, C. Zhao, X. Li, S. Deng, X. Lin, X. Yang, R. Li, H. Huang, L. Zhang, S. Lu, D. Su and X. Sun*, Nano Energy , 2020, 72, 104686.C. Wang, X. Li, Y. Zhao, M. N. Banis, J. Liang, X. Li, Y. Sun, K. R. Adair, Q. Sun, Y. Liu, F. Zhao, S. Deng, X. Lin, R. Li, Y. Hu, T.-K. Sham, H. Huang, L. Zhang, R. Yang, S. Lu and X. Sun*, Small Methods , 2019, 3, 1900261.C. Wang, J. Liang, M. Jiang, X. Li, S. Mukherjee, K. Adair, M. Zheng, Y. Zhao, F. Zhao, S. Zhang, R. Li, H. Huang, S. Zhao, L. Zhang, S. Lu, C. V. Singh and X. Sun*, Nano Energy, 2020, 76, 105015.C. Wang, R. Yu, S. Hwang, J. Liang, X. Li, C. Zhao, Y. Sun, J. Wang, N. Holmes, R. Li, H. Huang, S. Zhao, L. Zhang, S. Lu, D. Su and X. Sun*, Energy Storage Mater ., 2020, 30, 98-103.C. Wang, S. Hwang, M. Jiang, J. Liang, Y. Sun, K. Adair, M. Zheng, S. Mukherjee, X. Li, R. Li, H. Huang, S. Zhao, L. Zhang, S. Lu, J. Wang, C. V. Singh, D. Su, X. Sun*. Adv. Energy Mater., 2021, 2100210. doi:10.1002/aenm.202100210.C. Wang, Y. Zhao, Q. Sun, X. Li, Y. Liu, J. Liang, X. Li, X. Lin, R. Li, K. R. Adair, L. Zhang, R. Yang, S. Lu and X. Sun*, Nano Energy, 2018, 53, 168-174.C. Wang, Q. Sun, Y. Liu, Y. Zhao, X. Li, X. Lin, M. N. Banis, M. Li, W. Li, K. R. Adair, D. Wang, J. Liang, R. Li, L. Zhang, R. Yang, S. Lu and X. Sun*, Nano Energy, 2018, 48, 35-43.C. Wang, K. R. Adair, J. Liang, X. Li, Y. Sun, X. Li, J. Wang, Q. Sun, F. Zhao, X. Lin, R. Li, H. Huang, L. Zhang, R. Yang, S. Lu and X. Sun*, Adv. Funct. Mater. , 2019, 29, 1900392.

Recent progress in the function of redox mediators on the electrode/electrolyte interfaces of lithium–oxygen batteries

The nonaqueous lithium–oxygen batteries have attracted considerable interest because of the ultrahigh theoretical capacity. However, the overpotential and cyclability issue of lithium–oxygen battery caused by interfacial issue limits its commercialization. To overcome these challenges, redox mediators, which are capable of charge transport on the electrode/electrolyte interfaces, are introduced to lithium–oxygen batteries to reduce overpotential. This review provides a detailed summary of the interfacial reaction mechanism and the influence of redox mediators on the electrode/electrolyte interfaces. Researches on suppressing redox mediators’ shuttle effect are also beneficial to enhance the electrochemical performance of lithium–oxygen batteries.

Enhanced Fenton-like process via interfacial electron donating of pollutants over in situ Cobalt-doped graphitic carbon nitride

The heterogeneous Fenton process suffers from low efficiency because of the low electron transfer cycle rate of Fe3+/Fe2+, which often consumes enormous amounts of hydrogen peroxide (H2O2) or other energy. Herein, we report a novel Co-based Fenton-like catalyst (in-situ-Co-g-C3N4) synthesized via the surface complexation method, in which Co species were modified in situ into the framework of the graphitic carbon nitride (g-C3N4) substrate through C–O–Co chemical bonding. The catalyst exhibited higher Fenton-like catalytic activity than pure g-C3N4 in the degradation of various pollutants under neutral conditions, as evidenced by the approximately 150-fold higher Fenton-like reaction rate constant of in-situ-Co-g-C3N4 than that of g-C3N4. Density functional theory (DFT) calculations and a series of experimental and characterization analyses revealed the interfacial reaction mechanism between H2O2, pollutants and in-situ-Co-g-C3N4. During the Fenton-like reaction, the electron-poor C center on the aromatic ring of g-C3N4 could capture the electrons deprived from pollutants, and subsequently deliver them to around the electron-rich Co center to efficiently reduce H2O2 to hydroxyl radicals (•OH), enabling H2O2 to be used efficiently for the degradation of pollutants. This study provides a strategy for improving Fenton-like degradation efficiency by effectively utilizing the energy of organic pollutants.