Fast Charge Transfer Research Articles

Porphyrin conjugated polymer/Pt-loaded graphite carbon nitride nanocomposites for efficient charge separation and broadband responsive H2 evolution

An efficient broadband responsive two-dimensional (2D) heterometallic Zn-/Co-porphyrin conjugated polymer (ZnCoP-F CP) with its Co-porphyrin bridging unit bearing two perfluorophenyls is coupled with 2.0 wt% Pt-loaded graphite carbon nitride (PCN) to fabricate a novel 2D/2D nanocomposite (ZnCoP-F/PCN). The resultant ZnCoP-F/PCN composite with an optimal mass ratio exhibits broadband (UV–vis–NIR) responsive H2 evolution reaction (HER) activity up to 432 μmol h−1, 5.2 and 2.8 times higher than that of the ZnCoP-F CP (83 μmol h−1) and PCN (151 μmol h−1) alone, respectively. Furthermore, the ZnCoP-F/PCN displays excellent apparent quantum yields (AQY) of 18.2%, 18.3%, 17.6%, 16.5%, 13.9%, 8.7%, 5.1%, 4.3%, 1.9%, 0.95% and 0.62% at 350, 380, 420, 450, 500, 550, 600, 700, 785, 850 and 950 nm, which are also higher than that of ZnCoP-F CP illuminated at the respective monochromatic light. The enhanced broadband responsive HER performance of ZnCoP-F/PCN can be attributed to the easily assembled ZnCoP-F CP and PCN nanosheets through strong π–π stacking interaction, which can facilitate the fast charge transfer from ZnCoP-F CP to PCN for HER. This work opens a new pathway to fabricate porphyrin polymer-based nanocomposite for more efficiently converting solar radiation and water into H2.

Accelerated Intramolecular Charge Transfer in Tetracyanobutadiene- and Expanded Tetracyanobutadiene-Incorporated Asymmetric Triphenylamine–Quinoxaline Push–Pull Conjugates

The excited-state properties of an asymmetric triphenylamine–quinoxaline push–pull system wherein triphenylamine and quinoxaline take up the roles of an electron donor and acceptor, respectively, are initially investigated. Further, in order to improve the push–pull effect, powerful electron acceptors, viz., 1,1,4,4-tetracyanobutadiene (TCBD) and cyclohexa-2,5-diene-1,4-diylidene-expanded tetracyanobutadiene (also known as expanded-TCBD or exTCBD), have been introduced into the triphenylamine–quinoxaline molecular framework using a catalyst-free [2 + 2] cycloaddition–retroelectrocyclization reaction. The presence of these electron acceptors caused strong ground-state polarization extending the absorption well into the near-IR region accompanied by strong fluorescence quenching due to intramolecular charge transfer (CT). Systematic studies were performed using a suite of spectral, electrochemical, computational, and pump–probe spectroscopic techniques to unravel the intramolecular CT mechanism and to probe the role of TCBD and exTCBD in promoting excited-state CT and separation events. Faster CT in exTCBD-derived compared to that in TCBD-derived push–pull systems has been witnessed in polar benzonitrile.

Bidirectional Construction of 3D Flexible Ti3C2Tx MXene Films for High-Performance Lithium-Ion Capacitors

Lithium-ion capacitors (LICs) are considered ideal devices, which bridge the energy and power density gap between lithium-ion batteries (LIBs) and supercapacitors (SCs). However, the mismatched kinetics between the cathode and anode remains an obstacle to the development of LICs. Herein, an anode with excellent flexibility and fast electrochemical reaction kinetics is designed for advanced LICs by coupling highly conductive single-walled carbon nanotubes (CNTs) with the bidirectionally designed Ti3C2Tx MXene (KTi3C2-O). In such a composite (KTi3C2-O/CNTs), the bidirectional design of Ti3C2Tx MXene based on the interlayers of K+ ions intercalation and interfaces of −O terminal groups modification will increase the interlayer distance, provide more active sites, and improve Li+ ions storage capacity; the introduction of CNTs forming a three-dimensional (3D) interpenetrating structure with KTi3C2-O can alleviate Ti3C2Tx MXene interlayer stacking and offer fast charge transfer kinetics. When evaluated as a self-supported anode of LIC, the LIC displays a high power density of 15.63 kW kg–1, a high energy density of 138.89 Wh kg–1, and an exceptional capacity retention of 77.75% over 10 000 cycles at 5 A g–1. Such a bidirectional construction strategy based on interlayer and interfacial modification provides new ideas for the design of such two-dimensional (2D) materials that can be applied in advanced energy storage devices.

Photocathodic protection of 304 stainless steel by coating muscovite/TiO2 heterostructure

The sol-gel method was used to prepare a series of muscovite/TiO2 heterostructures for photocathodic protection of 304 stainless steels (304SS). The effects of different mass ratio of muscovite to TiO2 (1:0.5, 1:1 and 1:1.5, denoted as MT-0.5, MT-1 and MT-1.5, respectively) on the crystal phase, grain size, light absorption properties and photoelectrochemical properties of TiO2 and muscovite/TiO2 heterostructures were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and UV–visible diffuse reflection spectroscopy (UV–vis DRS). The corrosion resistances and photoelectrochemical properties of the 304SS coated with muscovite/TiO2 heterostructures (304SS/MT) were studied through corrosion immersion test and electrochemical workstation in 3.5 wt% NaCl solution, respectively. In addition, Tafel curves and the electrochemical impedance spectroscopy (EIS) measurements were carried out to evaluate the photogenerated electron separation and transfer efficiency, and the interfacial charge transfer resistance of the 304SS and 304SS/MT electrodes, respectively. The time-dependent photocurrent responses of the MT-1 heterostructures demonstrated an enhanced photo-generated cathodic protection performance for 304SS substrates under visible light irradiation compared to TiO2. A photoinduced potential drop value for 304SS coated with MT-1 in 3.5 wt% NaCl solution was −0.54 V (vs. SCE). After immersion test, the corrosion image analyses of the 304SS, 304SS-MT, and 304SS coated with physically mixed muscovite/TiO2 samples showed that the 304SS/MT-1 exhibits the best corrosion resistances. After connecting with 304SS/MT-1 in 3.5 wt% NaCl solution, the corrosion current densities (icorr) of 304SS increased significantly under the white light illumination, indicating more photoinduced electrons were migrated from the muscovite/TiO2 heterostructures to the 304SS compared with that from pure TiO2. Furthermore, the simulated charge transfer resistance (Rct) of 304SS/MT-1 electrode is smaller than that of the 304SS electrode coated with TiO2, indicating that there exists an effective separation of the photogenerated electrons and holes, and a fast interfacial charge transfer after coating muscovite/TiO2 heterostructures.

Semitransparent organic solar cells based on low temperature processed PEIE as electron transport layer with enhanced charge transfer ability

In inverted structure-based semitransparent organic solar cells (OSCs), the electron transport layer (ETL) plays a crucial role in the improvement of the transparent cathode efficiency in collecting and extracting negative charge carriers. Zinc oxide (ZnO) thin film prepared by zinc acetate dihydrate precursor with various benefits is generally used as ETL. However, high temperature, less charge transfer ability, and irregular film surface due to fiber-like domain formation limit the device performance. In this work, a new approach is presented by using low-temperature processed polyethylenimine ethoxylated (PEIE) as ETL in semitransparent OSCs fabricated in an ambient environment with a blend of low-bandgap donor polymer PTB7-Th, and fullerene acceptor, PC71BM, based active layer. For semitransparent OSCs, the thickness of the silver electrode has been varied from 55 nm to 25 nm to investigate its effect on the electrical and optical properties of the devices. The power conversion efficiencies (PCE) of 5.1% and 4.6% were achieved for semitransparent devices (25 nm thickness of silver electrode) for PEIE and ZnO ETLs, respectively. Similarly, PCE of 7% and 6.7% have been achieved for opaque devices (85 nm thickness of silver electrode) using PEIE and ZnO ETLs, respectively. PEIE based devices with 25 nm Ag demonstrate about 25%–30% transparency. The impedance spectroscopy measurements indicate low interfacial contact resistance and fast charge transfer capability for PEIE interlayer-based devices compared to the ZnO based devices. The encapsulated semitransparent devices processed and stored in ambient conditions with PEIE and ZnO ETLs were found to retain ≈80% performance for up to 45 days.

Hierarchical N-doped carbon nanofiber-loaded NiCo alloy nanocrystals with enhanced methanol electrooxidation for alkaline direct methanol fuel cells

The high catalytic activity of non-precious metals in alkaline media opens a new direction for the development of alkaline direct methanol fuel cell (ADMFC) electrocatalysts. Herein, a highly dispersed N-doped carbon nanofibers (CNFs) -loaded NiCo non-precious metal alloy electrocatalyst based on metal–organic frameworks (MOFs) was prepared, which conferred excellent methanol oxidation activity and resistance to carbon monoxide (CO) poisoning through a surface electronic structure modulation strategy. The porous electrospun polyacrylonitrile (PAN) nanofibers and the P-electron conjugated structure of polyaniline chains provide fast charge transfer channels, enabling electrocatalysts with abundant active sites and efficient electron transfer. The optimized NiCo/N-CNFs@800 was tested as an anode catalyst for ADMFC single cell and exhibited a power density of 29.15 mW cm−2. Due to the fast charge transfer and mass transfer brought by its one-dimensional porous structure and the synergistic effect between NiCo alloy, NiCo/N-CNFs@800 is expected to be an economical, efficient and CO-resistant methanol oxidation reaction (MOR) electrocatalyst.

Simultaneously Achieving Fast Intramolecular Charge Transfer and Mass Transport in Holey D-π-A Organic Conjugated Polymers for Highly Efficient Photocatalytic Pollutant Degradation.

Simultaneously realizing efficient intramolecular charge transfer and mass transport in metal-free polymer photocatalysts is critical but challenging for environmental remediation. Herein, we develop a simple strategy to construct holey polymeric carbon nitride (PCN)-based donor-π-acceptor organic conjugated polymers via copolymerizing urea with 5-bromo-2-thiophenecarboxaldehyde (PCN-5B2T D-π-A OCPs). The resultant PCN-5B2T D-π-A OCPs extended the π-conjugate structure and introduced abundant micro-, meso-, and macro-pores, which greatly promoted intramolecular charge transfer, light absorption, and mass transport and thus significantly enhanced the photocatalytic performance in pollutant degradation. The apparent rate constant of the optimized PCN-5B2T D-π-A OCP for 2-mercaptobenzothiazole (2-MBT) removal is ∼10 times higher than that of the pure PCN. Density functional theory calculations reveal that the photogenerated electrons in PCN-5B2T D-π-A OCPs are much easier to transfer from the donor tertiary amine group to the benzene π-bridge and then to the acceptor imine group, while 2-MBT is more easily adsorbed on π-bridge and reacts with the photogenerated holes. A Fukui function calculation on the intermediates of 2-MBT predicted the real-time changing of actual reaction sites during the entire degradation process. Additionally, computational fluid dynamics further verified the rapid mass transport in holey PCN-5B2T D-π-A OCPs. These results demonstrate a novel concept toward highly efficient photocatalysis for environmental remediation by improving both intramolecular charge transfer and mass transport.

Exploration of the lithium ions storage performance and mechanism of ZrN@reduced graphene oxide composite

The lithium ions storage behavior of zirconium nitride (ZrN) has been rarely explored. This work proposes a facile covalent self-assemble strategy to prepare the ZrN@reduced graphene oxide (ZrN@rGO) composite for enhanced lithium-ion battery (LIB). The X-ray photo spectra realizes that the strong Zr-C covalent bond is formed between ZrN and rGO. The Bader charge analysis features that the electron transferred from ZrN to rGO promotes the charge density at the ZrN@rGO heterointerface. Remarkably, the volume change decreases from 34% to 18% after the lithiation, corresponding to ZrN and ZrN@rGO, which highlights that the volume change of ZrN can be effectively alleviated by coupling with rGO. Further, the density functional calculation proves that the Li atom prefers to adsorb on Zr-N bridge site, and the adsorption energy of Li atom on ZrN@rGO (−2.01 eV) is higher than that on ZrN (−1.59 eV). Beyond that, the density of states of ZrN@rGO is significantly increased at the Fermi level, implying the high conductivity and fast charge transfer kinetics of ZrN@rGO. As a result, the specific capacity of ZrN@rGO remains at 199.5 mAh·g−1 at 1.0 A·g−1 after 1000 cycles.

M-N4-Gr/MXene Heterojunction Nanosheets as Oxygen Reduction and Evolution Reaction Catalysts: Machine Learning and Density Functional Theory Insights

MXene nanosheet materials with fast charge transfer characteristics and superior electrical conductivity are popular candidates for oxygen electrocatalysts. In this paper, the oxygen reduction and evolution reaction (ORR and OER, respectively) catalytic activities of 78 M-N4-Gr/MXene (Ti2C, Nb2C, and V2C) heterostructure nanosheets were investigated based on density functional theory (DFT) calculations and machine learning (ML) predictions. The random forest regression (RFR) algorithm proved to be the most desirable ML model for the prediction of catalytic activity with ORR/OER root mean square errors of 0.10 and 0.23 V, respectively. The obtained results show that Ni-N4-Gr/Nb2C (η*ORR = 0.31 V) and Ni-N4-Gr/V2C (η*ORR = 0.32 V) are effective ORR catalysts (prediction error of 0.03 V only), Ru-N4-Gr/Nb2C (η*OER = 0.40 V) is a promising OER catalyst, and Co-N4-Gr/V2C (η*ORR = 0.45 V/η*OER = 0.30 V) is an excellent bifunctional catalyst. Through further model analysis, the d band center of the metal active site was determined to be the most effective descriptor and a volcano curve relationship between the intrinsic descriptor and the overpotential was established based on the characteristic importance and Pearson correlation. The research approach adopted in this study may be used to screen and design other MXene heterojunction catalysts and remarkably accelerate catalyst design for many significant reactions.

Boosting aqueous zinc-ion storage by synergistically coupling sodium manganese oxides with MXene nanosheets

Aqueous zinc ion batteries (ZIBs) are regarded as a promising battery mainly due to their high safety and environmental friendliness, but suffer from low capacity and energy density. Herein, a pre-intercalated manganese oxide (Na0.55Mn2O4·1.5 H2O)/MXene hybrid (NMO/MXene) is successfully proposed for high-performance ZIBs, in which synergistic effect between MXene and NMO greatly improves the structural stability of NMO and facilitates fast charge transfer and ion diffusion kinetics. Therefore, the resulting NMO/MXene cathodes deliver high-rate capacity of 180 mAh g−1 at 10 C (3.08 A g−1) and long cycling life over 2500 times at 5 C, outperforming most reported Mn-base cathodes. The MXene-mediated strategy for advanced Mn-based cathodes developed here paves a new way to construct high-performance Zn-MnO2 batteries.

Environmental Footprint Assessment of Methylene Blue Photodegradation using Graphene-based Titanium Dioxide

To date, photocatalysis has received much attention in terms of the degradation of organic pollutants in wastewater. Various studies have shown that graphene-based photocatalysts are one of the impressive options owing to their intriguing features, including high surface area, good conductivity, low recombination rate of electron-hole pair, and fast charge separation and transfer. However, the environmental impacts of the photocatalysts synthesis and their photodegradation activity remain unclear. Thus, this report aims to identify the environmental impacts associated with the photodegradation of methylene blue (MB) over reduced graphene oxide/titanium oxide photocatalyst (TiO2/rGO) using Life Cycle Assessment (LCA). The life cycle impacts were assessed using ReCiPe 2016 v1.1 midpoint method, Hierachist version in Gabi software. A cradle-to-gate approach and a functional unit of 1 kg TiO2/rGOwere adopted in the study. Several important parameters, such as the solvent type (ultrapure water, ethanol, and isopropanol), with/without silver ion doping, and visible light power consumption (150, 300, and 500 W) were evaluated in this study. In terms of the selection of solvent, ultrapure water is certainly a better choice since it contributed the least negative impact on the environment. Furthermore, it is not advisable to dope the photocatalyst with silver ions since the increment in performance is insufficient to offset the environmental impact that it caused. The results of different power of visible light for MB degradation showed that the minimum power level, 150 W, could give a comparable photodegradation efficiency and better environmental impacts compared to higher power light sources. Copyright © 2023 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Bimetallic Fe, Ni-PBA on hollow graphite tube for capacitive deionization with exceptional stability

Faradic materials become more and more attractive for capacitive deionization (CDI) due to their high ion adsorption capacity. However, it is still a great challenge to design a stable and high charge-transfer rate material for high-performance desalination. Herein, we report a bimetallic Fe, Ni-doped Prussian blue analogue (PBA)-packed hollow graphite tube (FeNiHCF@HGT) electrode for boosting the CDI performance. The high conductivity of HGT and the tight adhesion of PBA crystals on HGT endow the FeNiHCF@HGT electrode with fast charge-transfer, excellent redox activity and high stability through buffering the crystal deformation of PBAs in the ion-intercalation/deintercalation process. In addition, the bimetallic Fe, Ni-doping in PBA at the high-spin (HS) sites enhances the redox activity of FeIIC6/ FeIIIC6 in FeNiHCF with Ni substitution for partial HS Fe. Under the optimal Ni-doping condition, the obtained Fe1Ni1HCF@HGT delivers a high specific capacity and superior rate performance (364F g−1 at 1 A g−1, 88.2% retention at 20 A g−1), with an ultra-high surface capacitance contribution (92.3% at 20 mV s−1). The CDI results demonstrate its outstanding salt adsorption capacity (60.2 mg g−1 in 100 mM NaCl) and exceptional cycle stability (106.6% retention after 100 cycles). This new strategy with the synergy of conductive tube matrix and Ni substitution at PBA lattice sites fully achieves the high-performance CDI.

Three-dimensional hierarchically porous micro sponge-ball comprising anatase TiO2 nanodots and nitrogen-doped graphitic carbon as anodes for ultra-stable lithium-ion batteries

Hierarchically porous three-dimensional micro sponge-balls comprising highly conductive nitrogen-doped graphitic carbon (NGC) and anatase-type TiO2 nanodots (TiO2@NGC MSB) are synthesized using spray pyrolysis technique followed by heat treatment. The as-sprayed powders obtained after spray pyrolysis consist of polystyrene (PS) nanobeads-derived macropores and anatase TiO2 nanodots embedded in an amorphous carbon (AC)-NGC carbon matrix (TiO2@NGC-AC MSB). The subsequent heat treatment of the as-sprayed powders at 300 °C resulted in the formation of additional micropores by selective removal of the AC into gaseous products to form TiO2@NGC MSB. The obtained hierarchically porous and highly conductive architecture guarantees effective electrolyte infiltration inside the electrode, enhanced Li-ion diffusion, and faster charge transfer during the redox reactions. Benefited from the structural merits, the TiO2@NGC MSB anode exhibits remarkable electrochemical performance compared to those of TiO2@NGC-AC MSB and filled-type TiO2 anodes. A reasonable discharge capacity of 105 mA h g−1 at a high current density of 10.0 A g−1 and exceptional cycling performance (219 mA h g−1 with 0.0006 % decay rate after 2000 cycles at 2.0 A g−1 and 160 mA h g−1 with 0.003 % decay rate after 5000 cycles at 3.0 A g−1) are obtained.

Ti3C2Tx MXenes bonded MoS2 nanosheets for superior sodium-ion batteries

Sodium-ion batteries (SIBs) have evolved into the most potential alternatives to lithium-ion batteries (LIBs) especially for large-scale energy storage applications. However, the large radius of sodium ion inevitably causes large volume change and sluggish ion diffusion kinetics. Molybdenum disulfide (MoS2) as a rising star of anode for SIBs has raised concern because of its high theoretical capacity. Nevertheless, MoS2 suffers from low electronic conductivity and serious re-stacking, resulting in declined cycling stability and poor rate capability. Herein, we reported an electrostatic self-assembly process to synthesize three-dimensional (3D) crumpled MXene-bonded MoS2 nanosheets. The MoS2/MXene heterostructure not only avoids the serious self-aggregation of MoS2 nanoparticles but only maintains the chemical and mechanical stability of MoS2/MXene hybrids during sodiation and desodiation. Strong chemical interactions were validated on the interface of MXene and MoS2, favoring fast charge transfer kinetics and durable structural stability. The developed MoS2/MXene electrode exhibits a high specific capacity (509 mAh g−1 at 0.05 A g−1) and considerable cyclability (326 mAh g−1 at 1 A g−1 after 900 cycles), manifesting a promising application prospect for SIBs. Our work can provide a rational strategy for the electrode design strategy for SIBs.

High‐efficiency sodium storage of Co0.85Se/WSe2 encapsulated in N‐doped carbon polyhedron via vacancy and heterojunction engineering

AbstractWith the advantage of fast charge transfer, heterojunction engineering is identified as a viable method to reinforce the anodes' sodium storage performance. Also, vacancies can effectively strengthen the Na+ adsorption ability and provide extra active sites for Na+ adsorption. However, their synchronous engineering is rarely reported. Herein, a hybrid of Co0.85Se/WSe2 heterostructure with Se vacancies and N‐doped carbon polyhedron (CoWSe/NCP) has been fabricated for the first time via a hydrothermal and subsequent selenization strategy. Spherical aberration‐corrected transmission electron microscopy confirms the phase interface of the Co0.85Se/WSe2 heterostructure and the existence of Se vacancies. Density functional theory simulations reveal the accelerated charge transfer and enhanced Na+ adsorption ability, which are contributed by the Co0.85Se/WSe2 heterostructure and Se vacancies, respectively. As expected, the CoWSe/NCP anode in sodium‐ion battery achieves outstanding rate capability (339.6 mAh g−1 at 20 A g−1), outperforming almost all Co/W‐based selenides.

Core-shell heterostructure by coupling layered ReS2 with Co9S8 nanocubes for boosted oxygen evolution reaction

The controllable morphology and composition of catalysts are crucial to improving the electrocatalytic activity of oxygen evolution reaction (OER). Herein, we construct a bimetallic heterostructure by sulfidation and hydrothermal methods, and the layered ReS2 is vertically aligned on Prussian blue-derived hollow Co9S8 nanocubes (Co9S8@ReS2). The core-shell structure of Co9S8@ReS2 can effectively prevent the restacking of layered ReS2, expose the abundant surface area and improve the utilization of electrocatalytic sites, resulting in fast electrolyte diffusion and charge transfer during OER. Due to the synergistic effect of the core-shell morphology and the formed bimetallic heterostructure, Co9S8@ReS2 exhibits excellent catalytic OER performance. At 10 mA/cm2, only 288 mV of overpotential is required with the Tafel slope of 73.3 mV/dec for Co9S8@ReS2, which are both lower than that of Co9S8 and ReS2. Meanwhile, Co9S8@ReS2 exhibits high catalytic stability and low charge transfer resistance and the boosted active sites are confirmed by density functional theory. This work provides a rational design of the OER catalysts by constructing the bimetallic heterostructure.

Graphene Oxide: Key to Efficient Charge Extraction and Suppression of Polaronic Transport in Hybrids with Poly (3-hexylthiophene) Nanoparticles.

Nanoparticles (NPs) of conjugated polymers in intimate contact with sheets of graphene oxide (GO) constitute a promising class of water-dispersible nanohybrid materials of increased interest for the design of sustainable and improved optoelectronic thin-film devices, revealing properties exclusively pre-established upon their liquid-phase synthesis. In this context, we report for the first time the preparation of a P3HTNPs-GO nanohybrid employing a miniemulsion synthesis approach, whereby GO sheets dispersed in the aqueous phase serve as a surfactant. We show that this process uniquely favors a quinoid-like conformation of the P3HT chains of the resulting NPs well located onto individual GO sheets. The accompanied change in the electronic behavior of these P3HTNPs, consistently confirmed by the photoluminescence and Raman response of the hybrid in the liquid and solid states, respectively, as well as by the properties of the surface potential of isolated individual P3HTNPs-GO nano-objects, facilitates unprecedented charge transfer interactions between the two constituents. While the electrochemical performance of nanohybrid films is featured by fast charge transfer processes, compared to those taking place in pure P3HTNPs films, the loss of electrochromic effects in P3HTNPs-GO films additionally indicates the unusual suppression of polaronic charge transport processes typically encountered in P3HT. Thus, the established interface interactions in the P3HTNPs-GO hybrid enable a direct and highly efficient charge extraction channel via GO sheets. These findings are of relevance for the sustainable design of novel high-performance optoelectronic device structures based on water-dispersible conjugated polymer nanoparticles.

Tubular Polypyrrole with Chloride Ion Dopants as an Ultrafast Organic Anode for High-Power Lithium-Ion Batteries.

Polypyrrole (PPy), as a representative p-type conductive polymer, attracts wide attention for energy storage materials. However, the sluggish reaction kinetics and low specific capacity of PPy impede its application in high-power lithium-ion batteries (LIBs). Herein, tubular PPy with chloride and methyl orange (MO) anionic dopants is synthesized and investigated as an anode for LIBs. The Cl- and MO anionic dopants can increase the ordered aggregation and the conjugation length of pyrrolic chains, forming plentiful conductive domains and affecting the conduction channel inside the pyrrolic matrix, thereby achieving fast charge transfer and Li+ ion diffusion, low ion transfer energy barriers, and rapid reaction kinetics. On account of the above synergistic effect, PPy electrodes deliver a high specific capacity of 2067.8 mAh g-1 at 200 mA g-1 and a remarkable rate capacity of 1026 mAh g-1 at 10 A g-1 , realizing high energy density (724 Wh kg-1 ) and power density (7237 W kg-1 ) simultaneously.

Electrocatalytic performance of Pd-based electro-catalysts supported on CNTs for isopropanol and ethanol electro-oxidation in alkaline medium

Palladium carbon nanotubes and palladium-niobium carbon nanotubes electro-catalysts were successfully prepared through the alcohol reduction method. The composition and morphology of the synthesized electro-catalysts were examined using different physicochemical characterization techniques such as Field Emission Scanning Electron Microscopy, High-Resolution Transmission Electron microscopy, and X-ray photoelectron spectroscopy. High-Resolution Transmission Electron microscopy revealed hollow tubular structures showing multi-walled carbon nanotubes with palladium-niobium nanoparticles deposited on their surface with an average particle size of 5.02 nm. The electrochemical behavior of palladium carbon nanotubes and palladium-niobium carbon nanotubes for isopropanol and ethanol electro-oxidation were investigated through cyclic voltammetry, chronoamperometry, and electrochemical impedance spectroscopy techniques. Palladium-niobium carbon nanotubes bimetallic electro-catalyst demonstrated better poisoning tolerance and the highest electrocatalytic activity through low Tafel slopes, low onset potentials, and fast charge transfer kinetics compared to palladium carbon nanotubes monometallic and the commercial palladium on carbon. The addition of niobium modified the structure of palladium through the electronic effect, weakening the binding strength of carbonaceous species on the surface of palladium and thus increasing its electrocatalytic activity. The obtained results provided essential insights into palladium-niobium carbon nanotubes as promising electro-catalysts for direct alcohol fuel cells.

One-pot self-assembled two-dimensional Ni/Ni3C/C3N4 nanosheets with highly efficient glucose oxidation for fuel cell and sensing applications

As the main reaction in both the glucose fuel cells and sensors, glucose oxidation reaction (GOR) is vital to their properties. In this work, we present a highly efficient GOR catalyst with two-dimensional sheet-like structures, which was prepared through one-pot self-assembled process. The as prepared Ni/Ni3C/C3N4 nanosheets with thickness less than 50 nm were composed of many Ni/Ni3C nanoparticles less than 5 nm anchoring on C3N4 sheets. Electrochemical characterizations confirmed that Ni/Ni3C/C3N4 nanosheets have the excellent GOR performance. The glucose fuel cells equipped with Ni/Ni3C/C3N4 nanosheets anodes (599.68 μW·cm−2) displayed greater power density than that of Ni, Ni3C, and C3N4 with the maximum power density obtained at 0.41 V. Moreover, the superior non-enzymatic glucose sensing performance was also obtained on Ni/Ni3C/C3N4 nanosheets electrodes, including high sensitivity (395.08μA.mM−2.cm−2 in range of 0–1000 μM and 163.64μA.mM−2.cm−2 in range of 1000 μM - 12000 μM), low detection limit (0.33 μM), good stability and repeatability. The high performance of Ni/Ni3C/C3N4 nanosheets may be due to the fast charge and mass transfer originating from the synergistic effect of Ni/Ni3C and C3N4 nanosheets.