Good Electronic Conductivity Research Articles

Tailoring surface chemistry of MXenes to boost initial coulombic efficiency for lithium storage

MXenes are expected to exhibit excellent lithium-ion storage performance due to its good electron conductivity, tunable functional groups, and unique accordion-like structure. However, they suffer from low initial coulombic efficiency (ICE) caused by the trapping and the irreversible reaction between MXene nanosheets and lithium ions. In this work, we propose a facile d-band center regulation strategy via doping engineering to achieve tailorable surface chemistry of MXene, revealing the intrinsic effects of heteroatoms doping on surface chemistry and ICE. This strategy can be applied to various MXenes, which is verified in the case of V2-yCryC as well as TiNbC, and TiVC MXenes. Typically, the V1.8Cr0.2C MXene delivers a double lithium storage capacity in comparison to V2C MXene. Its ICE is improved from 60% to 86%, surpassing most state-of-the-art MXenes. Theoretical calculations reveal that the shift of the d-band center towards the Fermi level is induced by the introduction of Cr and responsible for the improved electrochemical performance. It increases its chemical affinity and absorbability for oxygen-containing functional groups and lithium ions, providing a favorable surface chemistry for efficient lithium storage. This work provides a new strategy to tailor the fine structures of MXenes for their further energy storage applications.

CoMo layered double hydroxide equipped with carbon nanotubes for electrocatalytic oxygen evolution reaction

To carry out effective resource reforming of sustainable electricity, hydrogen production by electrochemical water splitting provides an eco-friendly and economical way. Nevertheless, the oxygen evolution reaction (OER) at the anode is limited by the slow reaction process, which hinders the large-scale development and application of electrolysis technology. In this work, we present an electrocatalyst with superior OER performance, which attributed to the abundant active sites and good electronic conductivity. The two-dimensional CoMo Layered Double Hydroxide nanosheets are synthesized and deposited on conductive carbon nanotubes (CoMo LDH/CNTs), and then hybrid composites show better catalytic performance than their undecorated counterpart under identical conditions. Specifically, CoMo LDH/CNTs exhibit the low overpotential of 268 mV to obtain 10 mA cm−2 and satisfactory stability (more than 40 h). We emphasize that this hybridization strategy with a conductive supporting framework could design more abundant and low-cost OER electrocatalysts to minimize electrical energy consumption, thereby achieving efficient conversion between energy sources.

Co/Zn bimetallic organic framework nanoparticles on carbon fibers as cathode for a high-performance rechargeable aqueous Zn-ion hybrid supercapacitor

Zinc-ion hybrid supercapacitors (ZHCs) are attracting more attentions due to their high energy/power densities and safety. Pseudocapacitive materials can provide larger capacitances than carbon materials due to their specific faradaic processes. Metal-organic frameworks with good electronic conductivity and abundant redox functional groups are ideal cathodic materials. Herein, a bimetallic organic framework cathode (Co/Zn-ZIF(M24)@CC) is proposed as a high-performance cathode in Zn-ion hybrid supercapacitor. The Co/Zn-ZIF(M24)@CC cathode benefits from a dual-ion storage mechanism of the pseudocapacitive behavior of H+ and the electrical double-layer capacitance behavior of Zn2+, which is methodically explored by ex situ electroanalytic characterizations. The as-prepared Co/Zn-ZIF (M24)@CC electrode achieved the highest energy density of 124.6 Wh kg−1 at 49.2 W kg−1. This study lays the foundation for the rational design of metal-organic cathodes in ZHCs.

Physicochemical Confinement Effect Enables High-Performing Zinc-Iodine Batteries.

Zinc-iodine batteries are promising energy storage devices with the unique features of aqueous electrolytes and safer zinc. However, their performances are still limited by the polyiodide shuttle and the unclear redox mechanism of iodine species. Herein, a single iron atom was embedded in porous carbon with the atomic bridging structure of metal-nitrogen-carbon to not only enhance the confinement effect but also invoke the electrocatalytic redox conversion of iodine, thereby enabling the large capacity and good cycling stability of the zinc-iodine battery. In addition to the physical trapping effect of porous carbon with good electronic conductivity, the in situ experimental characterization and theoretical calculation reveal that the metal-nitrogen-carbon bridging structure modulates the electronic properties of carbon and adjusts the intrinsic activity for the reversible conversion of iodine via the thermodynamically favorable pathway. This work demonstrates that the physicochemical confinement effect can be invoked by the rational anchoring of a single metal atom with nitrogen in a porous carbon matrix to enhance the electrocatalytic redox conversion of iodine, which is crucial to fabricating high-performing zinc-iodine batteries and beyond by applying the fundamental principles.

Layered manganese phosphorus trisulfides for high‐performance lithium‐ion batteries and the storage mechanism

AbstractAlthough advanced anode materials for the lithium‐ion battery have been investigated for decades, a reliable, high‐capacity, and durable material that can enable a fast charge remains elusive. Herein, we report that a metal phosphorous trichalcogenide of MnPS3 (manganese phosphorus trisulfide), endowed with a unique and layered van der Waals structure, is highly beneficial for the fast insertion/extraction of alkali metal ions and can facilitate changes in the buffer volume during cycles with robust structural stability. The few‐layered MnPS3 anodes displayed the desirable specific capacity and excellent rate chargeability owing to their good electronic and ionic conductivities. When assembled as a half‐cell lithium‐ion battery, a high reversible capacity of 380 mA h g−1 was maintained by the MnPS3 after 3000 cycles at a high current density of 4 A g−1, with a capacity retention of close to or above 100%. In full‐cell testing, a reversible capacity of 450 mA h g−1 after 200 cycles was maintained as well. The results of in‐situ TEM revealed that MnPS3 nanoflakes maintained a high structural integrity without exhibiting any pulverization after undergoing large volumetric expansion for the insertion of a large number of lithium ions. Their kinetics of lithium‐ion diffusion, stable structure, and high pseudocapacitance contributed to their comprehensive performance, for example, a high specific capacity, rapid charge–discharge, and long cyclability. MnPS3 is thus an efficient anode for the next generation of batteries with a fast charge/discharge capability.

Robust Porous TiN Layer for Improved Oxygen Evolution Reaction Performance.

The poor reversibility and slow reaction kinetics of catalytic materials seriously hinder the industrialization process of proton exchange membrane (PEM) water electrolysis. It is necessary to develop high-performance and low-cost electrocatalysts to reduce the loss of reaction kinetics. In this study, a novel catalyst support featured with porous surface structure and good electronic conductivity was successfully prepared by surface modification via a thermal nitriding method under ammonia atmosphere. The morphology and composition characterization-confirmed that a TiN layer with granular porous structure and internal pore-like defects was established on the Ti sheet. Meanwhile, the conductivity measurements showed that the in-plane electronic conductivity of the as-developed material increased significantly to 120.8 S cm−1. After IrOx was loaded on the prepared TiN-Ti support, better dispersion of the active phase IrOx, lower ohmic resistance, and faster charge transfer resistance were verified, and accordingly, more accessible catalytic active sites on the catalytic interface were developed as revealed by the electrochemical characterizations. Compared with the IrOx/Ti, the as-obtained IrOx/TiN-Ti catalyst demonstrated remarkable electrocatalytic activity (η10 mA cm−2 = 302 mV) and superior stability (overpotential degradation rate: 0.067 mV h−1) probably due to the enhanced mass adsorption and transport, good dispersion of the supported active phase IrOx, increased electronic conductivity and improved corrosion resistance provided by the TiN-Ti support.

Aqueous metal-sulfide battery with enhanced stability achieved by a four-electron Ag2S electrode with a Cu2+/Cu+ redox charge carrier

Sulfur with high specific capacity is a promising candidate for electrode material of aqueous/nonaqueous metal-sulfide batteries, however, it suffers from poor cycle stability due to its poor conductivity, large volume change and shuttle effect of polysulfide. For the first time, this work employs a semiconductor Ag2S with good electronic conductivity as cathode of aqueous metal-sulfide batteries, which gives a four-electron electrode reaction through a three-step all-solid-state conversion reaction of Ag2S→Ag3CuS2→AgCuS→Cu2S with a specific capacity of 432 mAh g−1. Besides, low volume expansion and the elimination of shuttle effect due to the small Ksp of Ag2S contribute to satisfactory cycle performance. The as-proposed Cu-Ag2S battery shows an extremely low overpotential of 50 mV and excellent cycle performance of 9000 cycles, which are the lowest and highest values respectively among all the reported metal-sulfide batteries. By pairing with Zn of lower potential, a cascade Zn-Ag2S battery is designed and achieves high working voltage up to1.22 V successfully. After Ag2S fully reducing into Cu2S in discharge process, Cu2+ in the electrolyte can provide additional capacity for the battery, thus, the cascade battery design can achieve a higher energy density, representing a promising route to energy-dense aqueous batteries.

Optimization of graphite/silicon-based composite electrodes for lithium ion batteries regarding the interdependencies of active and inactive materials

Due to its high theoretical capacity, silicon is a promising active material candidate for the negative electrode of lithium ion batteries. One way to reduce the severe degradation of silicon during charge/discharge cycling, is to use blends of different active materials and a well-balanced ratio of active and inactive materials. To ensure high-energy densities while still maintaining good electronic conductivity and ionic mobility, the necessity of nano-scale conductive carbons within a graphite/silicon composite was evaluated in this study. In particular, the correlation of silicon particle size and the presence of conductive additive was studied in electrodes, predominantly consisting of graphite (15 wt% silicon). Carbon black as conductive additive has a high contact surface area, which can enhance the electronic conductivity within the electrode and thus the rate capability, however, it can also propagate parasitic side reactions. It was determined that composite electrodes containing micron-sized silicon particles depend on the addition of conductive additives with regard to electrochemical performance. Due to high contact area and small transport distances, electrodes based on nano-sized silicon showed comparable capacity retention and a higher specific discharge capacity. Omitting conductive particles from these composite electrodes allowed lower binder amounts, while maintaining a good mechanical electrode integrity.

ZIF-67 derived NiCoP nanosheets on carbon cloth as a flexible cathode for high-performance solid-state asymmetric supercapacitors

Herein, unique bimetallic phosphide of NiCoP with nanosheet structure coated on carbon cloth (NiCoP@CC) was synthesized. Three-dimensional cobalt-based ZIF-67 (Co-ZIF-67) with dodecahedron morphology was first grown on carbon cloth, and then the NiCoP nanosheets were formed through a synthesis procedure involving Ni2+-induced template scarification of the Co-ZIF-67 and the phosphorization calcination. Impressively, the resulting NiCoP@CC electrode shows a remarkable specific capacity of 1149.2 C g−1 (6.09 C cm−2) at 1 A g−1 and superior cycle performance (the capacity retains 99.7 % after cycled for 10,000 cycles at 6 A g−1), owing to the optimized ZIF-67-template modification, unique morphology, good electronic conductivity, superiority of the bimetallic phosphides, and the battery type feature. Further, a solid-state asymmetric supercapacitor (ASC) was fabricated by using the obtained NiCoP@CC as the cathode and using active carbon (AC) as the anode. The assembled ASC device delivers a high specific energy of 78.5 Wh kg−1 at the specific power of 799.5 W kg−1, and remains 90.3 % capacity retention over 10,000 cycles at 8 A g−1, demonstrating its high potential for applications in the field of high-capacity supercapacitors. These results illustrate the promise of NiCoP@CC as a promising cathode material in supercapacitor.

Steady State Performance Evaluation of Noble-Metal Free Bifunctional Electrode for Overall Water Splitting

The emerging need of clean and renewable energy drives the exploration of effective strategies to produce molecular hydrogen. With the assistance of highly active non-noble metal electrocatalysts, electrolysis of water is becoming a promising candidate to generate pure hydrogen with low cost and high efficiency. This reaction takes place almost exclusively on Pt/C catalysts at the cathode which is expensive and need to be replaced by a metal-based catalyst that is cost effective and can show a comparable HER (Hydrogen Evolution Reaction) activity. Transition metal oxides, nitrides and sulfides have been widely explored as catalysts for HER and OER (Oxygen Evolution Reaction) due to their good electronic conductivity, stable and variable oxidation states, and superior corrosion resistance. In this research, MoNi4 embedded MoO3 nanorods are synthesized using facile hydrothermal method. Further, Molybdenum Vanadium Nitride is coated on top the synthesized electrode using RF/DC magnetron co-sputtering. This combination of hydrothermal and magnetron sputtering fabrication methods of the electrodes results in high surface area of the electrodes thereby improving the reaction kinetics of hydrogen production. The performance of the electrodes is tested in N2/O2 saturated 1M KOH solution using steady state technique called Staircase Voltammetry (SCV) instead of conventional dynamic LSV (Linear Sweep Voltammetry)/CV (Cyclic Voltammetry). This alternative method for testing is performed due to the exaggeration of the catalytic performance through conventional LSV/CV arising from double layer charging for nanostructured electrode. The electrodes are characterized by X-ray diffraction and SEM for structural and morphological analysis. Hence, we report the synthesis of novel MoVN on MoNi4/MoO2 nanorods using DC/RF Magnetron co-sputtering as an efficient, bifunctional, binder free electrode for overall water splitting. The electrode is characterised for both full-cell and half-cell configurations proving its stability for 12 hours. This work provides a reliable approach to the production of low cost and high-effectiveness electrodes for the application in commercial electrolyzers.

Engineering Transition Metals As Noble-Metal Free Bifunctional Electrode for Overall Water Splitting

The emerging need of clean and renewable energy drives the exploration of effective strategies to produce molecular hydrogen. With the assistance of highly active non-noble metal electrocatalysts, electrolysis of water is becoming a promising candidate to generate pure hydrogen with low cost and high efficiency.[1] This reaction takes place almost exclusively on Pt/C catalysts at the cathode which is expensive and need to be replaced by a metal-based catalyst which can show a comparable HER (Hydrogen evolution reaction) activity. Transition metal oxides, nitrides and sulfides have been widely explored as catalysts for HER and OER (Oxygen evolution reaction) due to their good electronic conductivity, stable and variable oxidation states, and superior corrosion resistance.[2] In this research, MoNi4 embedded MoO3 nanorods are synthesized using facile hydrothermal method. Further, Molybdenum Vanadium Nitride is coated on top the synthesized electrode using RF/DC magnetron co-sputtering.[3] This combination of hydrothermal and magnetron sputtering fabrication methods of the electrodes results in high surface area of the electrodes thereby improving the reaction kinetics of hydrogen production. The performance of the electrodes is tested in N2/O2 saturated 1M KOH solution using steady state technique called Staircase Voltammetry (SCV) instead of conventional dynamic LSV (Linear sweep voltammetry)/CV (Cyclic Voltammetry).[4] This alternative method for testing is performed due to the exaggeration of the catalytic performance through conventional LSV/CV arising from double layer charging for nanostructured electrode. The electrodes are characterized by X-ray diffraction and SEM for structural and morphological analysis. Hence, we report the synthesis of novel MoVN on MoNi4/MoO2 nanorods using DC/RF Magnetron co-sputtering as an efficient, bifunctional, binder free electrode for overall water splitting. The electrode is characterised for both full-cell and half-cell configurations proving its stability for 12 hours. This work provides a reliable approach to the production of low cost and high-effectiveness electrodes for the application in commercial electrolyzers.[1] J. Zhang et al., “Efficient hydrogen production on MoNi4 electrocatalysts with fast water dissociation kinetics,” Nat. Commun., vol. 8, no. May, pp. 1–8, 2017, doi: 10.1038/ncomms15437.[2] L. A. Santillán-Vallejo et al., “Supported (NiMo,CoMo)-carbide, -nitride phases: Effect of atomic ratios and phosphorus concentration on the HDS of thiophene and dibenzothiophene,” Catal. Today, vol. 109, no. 1–4, pp. 33–41, 2005, doi: 10.1016/j.cattod.2005.08.022.[3] B. Wei et al., “Bimetallic vanadium-molybdenum nitrides using magnetron co-sputtering as alkaline hydrogen evolution catalyst,” Electrochemistry Communications, vol. 93. pp. 166–170, 2018, doi: 10.1016/j.elecom.2018.07.012.[4] S. Anantharaj and S. Kundu, “Do the Evaluation Parameters Reflect Intrinsic Activity of Electrocatalysts in Electrochemical Water Splitting?,” ACS Energy Lett., vol. 4, no. 6, pp. 1260–1264, 2019, doi: 10.1021/acsenergylett.9b00686. Figure 1

Solid Oxide Fuel Cells with 3D Inkjet Printing Modified LSM-YSZ Interface

Solid oxide fuel cells (SOFCs) have drawn attention as an alternative power generation technology due to demonstrated high efficiency and low emissions. The lanthanum strontium manganite (LSM)-yttria-stabilized zirconia (YSZ) cathode is utilized widely for SOFCs due to its high performance and stability. The electrochemical oxygen reduction reaction that occurs in the cathode can be enhanced by the porous LSM-YSZ cathode with good electronic and ionic conductivity. With sufficient electrochemically active reaction sites, the oxygen ion transfer processes in the mixed ionic conductor (YSZ) and at the interface of cathode and electrolyte (LSM-YSZ) become critical for the activity of the cathode. Thus, the pillar shape YSZ microstructure with ~ 150 μm×150 μm×10 μm (L×W×H) size can be fabricated by 3D inkjet printing on the interface of electrolyte and cathode to increase the TPB area and enhance the connection between the dense YSZ electrolyte and mixed YSZ ionic conductor. Scanning Electron Microscopy (SEM) is utilized to assess the morphology and microstructure of the YSZ interface. To investigate the influence of the modified interface on the performance of the SOFC, electrochemical performance testing and characterization are conducted for the SOFCs with/without the modified YSZ layer. The microstructures with different pillar central spacing are also fabricated by 3D inkjet printer to optimize the geometry of the LSM-YSZ interface.

Mechanism of Improved Lithium-Sulfur Battery Performance by Oxidation Treatment to Microporous Carbon as Sulfur Matrix

1. IntroductionLithium-sulfur (Li-S) batteries are rechargeable devices assembled with a sulfur cathode and a lithium metal anode. Li-S batteries have twice the volumetric energy density and 5 times the gravimetric energy density of lithium-ion batteries (LIB). Hence, Li-S batteries are expected to be applied to stationary power sources and EV vehicles [1]. However, Li-S batteries have the following issues:・Sulfur and the final discharge product (Li2S) are insulators.・In the discharge process, sulfur expands up to 1.8 times, so the structure of batteries is unstable.・Intermediate products (Li2Sx (x = 4 – 8)) dissolve in an electrolyte; Li2Sx (x = 4 – 8) diffused to an anode to provide an insulating layer at the anode surface.・In the charge process, Li2Sx (x = 4 – 8) causes redox shuttling.As a result, Li-S batteries cannot charge and discharge stably. In order to deal with this problem, Nazar et al. reported the method that sulfur is confined in porous carbon [2]. This approach provides a cathode realizing good electronic conductivity, restriction of sulfur expansion, and suppression of Li2Sx (x = 4 – 8) dissolution. Although these improved characteristics allow Li-S batteries to operate, The discharge capacity of Li-S batteries is still not high enough and this needs to be addressed.In our previous study, we reported that oxidation treatment to microporous carbon (MC) with HNO3 improves Li-S batteries' discharge capacity [3]. Moreover, we clarified that the discharge capacity of Li-S batteries has an approximate proportional relation with the amount of oxygen-containing functional groups on the MC surface [4].This work attempts to elucidate the mechanism of improved Li-S battery performance by oxidation treatment to MC. Our report would lead to the proposal of a novel strategy to improve the performance of Li-S batteries.2. Method2.1 Preparation of Oxidized MC-Sulfur composite (Ox MC-S)MC was added into 69 wt.% HNO3 and refluxed at 120ºC for 2 h. By vacuum filtration and washing with deionized water, Ox MC was obtained. Ox MC dried in vacuum at 80ºC overnight was mixed with sulfur at a weight ratio of Ox MC: S = 48: 52. The mixture was thermally annealed at 155ºC for 5 h (Ox MC-S). Untreated MC was also composited with sulfur by the same method (MC-S).2.2 Assembling of CellsEach MC-S cathode was prepared by mixing the MC-S, acetylene black, carboxymethyl cellulose, and styrene butadiene rubber at a respective weight ratio of 89: 5: 3: 3 and coating the resulting aqueous slurry on an Al foil current collector. The cells with the MC-S electrode and Li metal foil as an anode were assembled in a glove box filled with Ar. Lithium bis(trifluorosulfonyl)imide (LiTFSI): tetraglyme (G4): hydrofluoroether (HFE) = 10: 8: 40 (by mol) was used as the electrolyte.2.3 Electrochemical Impedance Spectroscopy (EIS)To elucidate the effect of oxidation treatment on the internal resistance of Li-S batteries, EIS was carried out at various potentials (Discharge 2.0 – 1.0 V and Charge 1.0 – 3.0 V). The obtained Nyquist plots were used for the evaluation of solid electrolyte interphase (SEI) resistance (Rsei), charge-transfer resistance (Rct), and Warburg impedance (Rw). Rw was investigated with the calculation of Warburg coefficient (σ).3. Major results and conclusionSince oxidation treatment to MC significantly increased the discharge capacity of Li-S batteries [3][4], it was expected that oxidation treatment would lower the internal resistance of Li-S batteries. EIS of MC-S and Ox MC-S at various potentials showed that oxidation treatment reduced Rsei by an average of 12.2 Ω. This indicates that the SEI thickness was reduced, or the SEI was composed of highly ion-conductive components by the oxidation treatment. Rct decreased only at lower potentials, and the Warburg coefficient decreased except at the end of charge and discharge potential. These results suggest that the oxidation treatment decreases overall resistance, but especially SEI resistance and Warburg impedance, which may improve the discharge capacity of Li-S batteries.We will also report the activation energy of Rsei and Rct and mechanism analysis of decreasing Rsei by oxidation to MC. This work was supported by “Advanced Low Carbon Technology Research and Development Program, Specially Promoted Research for Innovative Next Generation Batteries (ALCA-SPRING [JPMJAL1301])” from JST.[1] Y. Guo et al., Angew. Chem. Int. Ed., 52 (2013) 13186.[2] X. Ji et al., Nat. Mater., 8 (2009) 500.[3] S. Okabe et al., Electrochemistry, 85 (2017) 671.[4] L. Yoshida et al., ECS 238th PRiME Meeting s (2020).

A high-purity AgO cathode active material for high-performance aqueous AgO–Al batteries

The aqueous divalent silver oxide (AgO)-aluminum (Al) batteries have garnered international attention due to the advantages of high safety, high specific energy, and environmental friendliness. However, the low purity of the AgO used as the cathode material shortens the battery's storage life and causes two voltage plateaus during discharge. Herein, we employ a quick and efficient approach to make AgO for aqueous AgO–Al batteries' cathode active material. The outcomes exhibit the successful production of high purity AgO with good thermal stability. The prepared AgO cathode additionally displays an excellent specific capacity of 394.7 mAh g−1, and the plateau of the discharge profile is closed to 1.7 V at the current density of 500 mA cm−2, taking advantage of the good electronic conductivity and charge transfer kinetics. A maximum output power density of 1260.54 mW cm−2 at 900 mA cm−2 is also possible. Furthermore, the electrochemical mechanism of the AgO electrode is further uncovered by Ex-situ X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), and transmission electron microscope (TEM) studies. Thus, this research presents a viable possibility for the fabrication of aqueous AgO–Al batteries by demonstrating the use of high purity AgO as a cathode active material.

Cathodic photoelectrochemical sensor developed for glutathione detection based on carrier transport in a Ti3C2Tx/AgI heterojunction

Recently, cathodic photoelectrochemical (PEC) sensing has emerged as a convenient and efficient method for molecular detection and analysis. Novel photoactive materials are urgently required for the further development of advanced cathodic PEC sensors. In this study, an original photoactive material, the Ti3C2Tx/AgI heterojunction material (HM), was synthesized by combining the two-dimensional layered material Ti3C2Tx MXenes with the p-type semiconductor AgI. The Ti3C2Tx/AgI HM exhibited excellent PEC performance. The PEC process in the Ti3C2Tx/AgI HM under light irradiation was explored and demonstrated using Vienna abinitio simulation package (VASP) calculations. The Ti3C2Tx/AgI HM exhibited enhanced electron–hole separation and charge transport owing to the good electronic conductivity of Ti3C2Tx and improved interfacial electron transport from Ti3C2Tx to AgI. Therefore, a cathodic PEC sensor was developed for glutathione (GSH) detection. GSH acted as a reductant and consumed the electron acceptor to inhibit electron transfer, resulting in a decrease in photocurrent signals that was linear with the GSH concentration. The linear range was wide (1–10 μM), with a detection limit of 0.31 nM. The PEC sensor also displayed satisfactory selectivity and stability; thus, the findings provide insights into the design and construction of a PEC sensing platform without enzymes.

Heterostructured MXene-derived oxides as superior photocatalysts for MB degradation

This work offers a simple and effective strategy to design a two-dimensional layer heterostructure of carbon/Ti-based oxide nanocomposites via a long-term oxidation process of MXene (Ti 3 C 2 T x ). Oxidation kinetics parameters concluded that MXene initially reacted with oxygen by forming the carbon layer and nanostructured Ti-based oxides with a homogeneous distribution, including TiOF 2 and TiO 2 , whereas the further oxidation process was governed by oxygen diffusion. It suggested that lower oxidation temperature and longer time (300 °C/1 h) facilitated to fabricate carbon-supported TiO 2 @TiOF 2 heterojunction nanocomposites with a unique 2D layer structure, which achieved a 90 % removal of methylene blue (MB) at 1 h under visible light illumination, owning to its large specific surface area, good electronic conductivity, narrowed band-gap, enhanced absorption in the visible range and high charge separation efficiency. Hence, the designed MXene-derived oxides were considered as promising candidates for wide-range responsive photocatalytic degradation of pollutants. ● Ti-based oxides with different architecture were constructed via isothermal oxidation treatment of MXene (Ti 3 C 2 T x ). ● Oxidation of Ti 3 C 2 T x was initially governed by the surface reaction, and then controlled by the oxygen diffusion process. ● Lower temperature and longer holding time was the optimal oxidation condition to construct 2D C/TiO 2 @TiOF 2 heterojunction.

In-situ embedding Co9S8 nanoparticles in polyaniline-based carbon nanotubes for enhanced lithium storage

In this work, Co 9 S 8 nanoparticles embedded polyaniline-based carbon nanotubes (Co 9 S 8 /C nanotubes) have been prepared vis polymerization of aniline, rotary evaporation and further calcination, in which the melamine tubes from protonated melamine under the induction of NO 3 - , serve as templates for the preparation of PAIN tubes by polymerization. After calcination, PANI-based carbon nanotubes provide a good carrier for Co 9 S 8 nanoparticles. The N doping in the carbon nanotubes and unique structure endow Co 9 S 8 /C nanotubes with good electronic and ionic conductivity. As a result, Co 9 S 8 /C nanotubes show favorable rate capability (645 mA h g −1 at 0.2 A g −1 and 524 mA h g −1 at 0.5 A g −1 ) and superior cycling performance at 1.0 A g −1 for 500 cycles, making them promising anode candidate for high-performance lithium-ion batteries. • Nano Co 9 S 8 embedded PANI-based carbon nanotubes are prepared by in-situ strategy. • Melamine tubes act as sacrificial template for the synthesis of Co 9 S 8 /C nanotubes. • Co 9 S 8 /C nanotubes show favorable performances as anode materials for LIBs.

High thermoelectric figure of merit in rhombic porous carbon nitride nanoribbons

AbstractBy performing extensive density functional theory calculations combined with non‐equilibrium Green's function technique, we predict the rhombic porous carbon nitride nanoribbon (rPCNNR) and the vertical rPCNNR junction exhibiting high thermoelectric figure of merit (ZT) values of 0.57 and 2.1 at room temperature respectively. Theoretical results reveal that the ZT value of rPCNNR is significantly larger than that of armchair graphene nanoribbon with the almost same width (~0.035) due to the large Seebeck coefficients and the significantly decreased thermal conductance of rPCNNR, where the phonon states are blocked by the built‐in porous structure and rhombic edge in rPCNNR. The ZT value is further enhanced to be 2.1 in the vertical rPCNNR junction, which is achieved by the synergy effect between the dramatically suppressed thermal conductance in in‐plane direction due to the weak van der Waals interaction between two rPCNNRs, the almost unchanged Seebeck coefficients, and the good electron conductivity provided by the strong overlapping of delocalized VB‐ and CB‐derived states in the scattering region. These presented findings highlight rPCNNR as a promising candidate in building flexible devices with high thermoelectric performance.

Two-dimensional penta-siligraphene with high performance for non‑lithium metal ions batteries anode materials

Non‑lithium metal ion batteries (NLMIBs) will play an important part in sustainable energy and grid storage. Searching for high-performance electrode materials are critical to the development of NLMIBs. From first-principles calculations, we predict that penta-siligraphene (P-Si2C4), a new two-dimensional (2D) layered material obtained by replacing the sp3 C atoms in penta-graphene with Si atoms, can be used as a promising anode material for NLMIBs including Na-, K-, Rb-, Ca-, Sr- and Ba-ion. The theoretical specific capacities for Na, Sr, Ba, Rb, K and Ca ions are 514.3, 1028.7, 1028.7, 578.6, 1028.7 and 2057.3 mA h g−1, respectively. The metal-ion intercalation potentials (0.1–1.0 V) are suitable for battery application. After metal-ions adsorbed, the electronic structures of P-Si2C4 become metallic indicating of good electronic conductivity of the anode. The metal-ion/vacancy diffusion energy barriers on the surface of P-Si2C4 are relatively small and ensure good rate performance. Our research offers a promising high performance anode material for the application in NLMIBs.

Concentrating photoelectrons on sulfur sites of ZnxCd1–xS to active H–OH bond of absorbed water boosts photocatalytic hydrogen generation

Highly hydrophobic polypyrrole (PPy), as a promising conjugated polymer with good electron conductivity and excellent environmental stability, has received active attention in various fields. As is well known, the adsorption and dissociation of water molecules are the rate–limiting step of photocatalytic hydrogen evolution (PHE) reaction in the alkaline media. Herein, highly–hydrophilic polypyrrole–poly(sodium–p–styrenesulfonate) (PPy–PSS) were sectionally wrapped on the surface of ZnxCd1–xS (ZCS) nanorods via redox initiate polymerization to improve the hydrophily of ZCS, which favors water absorption. The density functional theory (DFT) calculation shows the sulfur electronic structure of ZCS is modulated in PPy–PSS–ZCS (PP–ZCS) composite. Specifically, the constituent PPy and PSS polymers through strong electronic interactions with ZCS could improve the water dissociation and the adsorption/desorption of hydrogen intermediates on ZCS component. After activating H–OH bond, the optimized PP–ZCS composite reveals an improved PHE efficiency of 46.1 mmol h−1 g−1 without an obvious decrease for continuous 24 h in visible light, which is 8.67 and 1.68 times higher than those of ZCS and PPy–ZCS. This strategy paves a new way for activating ZnxCd1–xS–based composite by highly hydrophilic and conductive conjugated polymer.