Fast Charge Transfer Kinetics Research Articles

A strategy of boosting the effect of carbon nanotubes in graphite-blended Si electrodes for high-energy lithium-ion batteries

High capacity silicon (Si) has been added in graphite electrodes to overcome the theoretical capacity limit of the carbonaceous anode. However, different active materials that store Li+ ions via intercalation and alloying mechanisms are prone to suffer electrical disconnection due to the large gap derived from their different volume shrinkage ratios during delithiation. Herein, to address this poor compatibility on graphite-blended Si composite electrode (Gr-SC), a strategic usage of carbon nanotubes (CNTs) as electric bridge between graphite and Si is investigated through the comparison of three different types of Si blended graphite anodes (Gr-SC, Gr-SC with CNTs as additive, and Gr-MSC having implanted multi-walled CNTs on Si). Among the comparison group, the selectively located MW-CNT around Si in Gr-MSC exhibits outperformed capacity retention (98.4 %) and faster charge transfer kinetics after 50 cycles in a half cell, demonstrating a great compatibility between graphite and Si. This study presents a comprehensive understanding on the role of CNTs as an electric bridge on the electrode exploiting multiple Li storage mechanisms which undergo dissimilar volume change.

Boosting the activity and CO tolerance for methanol oxidation reaction in alkaline media by constructing the Pt-TMNs electrocatalysts

Developing the efficient and high CO tolerance electrocatalysts is important for methanol oxidation reaction. In this study, a sequence ofcatalysts were constructed by introducting various transition metal nitrides (TMNs) to modify the Pt/C catalyst. The corresponding electrochemical performance were evaluated to investigate the activity, kinetics, charge transfer rate, CO tolerance and stability for MOR in alkaline media. Based on the structural characterization analysis from ICP-MS, XRD, HRTEM and XPS, it could be indicated that the participation of TMNs mainly brought the electronic effect, but not for the geometric effect. The evident difference did not exist in the nanoparticle size, morphology and crystallinity of the related catalysts. After the evaluation on the catalytic performance for alkaline MOR, The TMNs-modified catalysts exhibited higher activity and lower onset potential potential compared with the commercial Pt/C. Among them, Pt-NbN/C showed the highest mass activity with 9.56-fold that of the commercial Pt/C. The faster charge transfer kinetics and reaction rate were confirmed by Tafel and EIS results. CA measurements indicated that they also exhibited higher stability and anti-CO poisoning ability for alkaline MOR, consistent with the CO stripping experiments. To quantitatively describe the realtionship of the electronic effect on the catalytic activity and CO tolerance, the d-band center was employed as a parameter to bulid the corresponding function. Interestingly, it was proposed that the rational d-band center could lead high MOR performance and anti-CO poisoning ability. The introduction of TMNs brought the evident shift of the Pt d-band center and boosted the catalytic activity and anti-CO poisoning ability for alkaline MOR.

Improved Electrochemical Performance of Ni2P2O7 and Mn‐doped Ni2P2O7 Electrode Materials for Supercapacitor Applications

AbstractThe development of electrode materials for supercapacitors is really progressive and it still poses a huge challenge for researchers in many aspects. Doping of transition metals is indeed effective method because fast interfacial charge transfer kinetics has demonstrated their potential supercapacitive nature. The present work submits the structural, morphological and electrochemical performances of nickel pyrophosphate (Ni2P2O7) and manganese doped nickel pyrophosphate (Mn‐Ni2P2O7) thin film electrodes synthesized by chemical bath deposition method. The crystal structure of Ni2P2O7 obtained through X‐ray diffraction (XRD) is confirmed to be monoclinic which remains unaltered despite of Mn doping concentration. Morphological studies reveal that crystalline phase of Mn is intimately anchored on the surface of Ni2P2O7 which is beneficial for better charge transfer between transition metal and transition metal phosphates. A specific capacitance value of 603 F/g is obtained for 3 M concentration of Mn doped Ni2P2O7 from galvanostatic charge‐discharge curve at current density 1 A/g. This value is noticeably higher than what is obtained for the pure Ni2P2O7 indicating that Mn doping enhances the electrochemical performance of Ni2P2O7 thin films.

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.

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.

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.

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.

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.

A Bifunctional Electrocatalyst for OER and ORR based on a Cobalt(II) Triazole Pyridine Bis-[Cobalt(III) Corrole] Complex.

As alternative energy sources are essential to reach a climate-neutral economy, hydrogen peroxide (H2O2) as futuristic energy carrier gains enormous awareness. However, seeking for stable and electrochemically selective H2O2 ORR electrocatalyst is yet a challenge, making the design of-ideally-bifunctional catalysts extremely important and outmost of interest. In this study, we explore the application of a trimetallic cobalt(II) triazole pyridine bis-[cobalt(III) corrole] complex CoIITP[CoIIIC]2 3 in OER and ORR catalysis due to its remarkable physicochemical properties, fast charge transfer kinetics, electrochemical reversibility, and durability. With nearly 100 % selective catalytic activity towards the two-electron transfer generated H2O2, an ORR onset potential of 0.8 V vs RHE and a cycling stability of 50 000 cycles are detected. Similarly, promising results are obtained when applied in OER catalysis. A relatively low overpotential at 10 mA cm-2 of 412 mV, Faraday efficiency 98 % for oxygen, an outstanding Tafel slope of 64 mV dec-1 combined with superior stability.

A Bifunctional Electrocatalyst for OER and ORR based on a Cobalt(II) Triazole Pyridine Bis-[Cobalt(III) Corrole] Complex.

As alternative energy sources are essential to reach a climate-neutral economy, hydrogen peroxide (H2 O2 ) as futuristic energy carrier gains enormous awareness. However, seeking for stable and electrochemically selective H2 O2 ORR electrocatalyst is yet a challenge, making the design of-ideally-bifunctional catalysts extremely important and outmost of interest. In this study, we explore the application of a trimetallic cobalt(II) triazole pyridine bis-[cobalt(III) corrole] complex CoII TP[CoIII C]2 3 in OER and ORR catalysis due to its remarkable physicochemical properties, fast charge transfer kinetics, electrochemical reversibility, and durability. With nearly 100 % selective catalytic activity towards the two-electron transfer generated H2 O2 , an ORR onset potential of 0.8 V vs RHE and a cycling stability of 50 000 cycles are detected. Similarly, promising results are obtained when applied in OER catalysis. A relatively low overpotential at 10 mA cm-2 of 412 mV, Faraday efficiency 98 % for oxygen, an outstanding Tafel slope of 64 mV dec-1 combined with superior stability.

Manipulating Polymer Backbone Configuration via Halogenated Asymmetric End-Groups Enables Over 18% Efficiency All-Polymer Solar Cells.

High-performance all-polymer solar cells (all-PSCs) deeply rely on the joint contributions of desirable optical absorption, adaptive energy levels, and appropriate morphology. Herein, two structural analogous polymerized small-molecule acceptors (PSMAs), PYFCl-T and PYF&PYCl-T, are synthesized, and then incorporated into the PM6:PY-IT binary blends to construct ternary all-PSCs. Due to the superior compatibility of PY-IT and PYFCl-T, theternary all-PSC based on PM6:PY-IT:PYFCl-T with 10 wt% PYFCl-T, presents higher and more balanced charge mobility, suppressed charge recombination, and faster charge-transfer kinetics, resulting in an outstanding power conversion efficiency (PCE) of 18.12% with enhanced Jsc and FF, which is much higher than that (PCE of 16.09%) of the binary all-PSCs based on PM6:PY-IT. Besides, the ternary all-PSCs also exhibit improved photostability. The conspicuous performance enhancement principally should give the credit to the miscibility-driven phase optimization of the donor and acceptor. These findings highlight the significance of polymer-backbone configuration modulation of PSMAs in morphology optimization toward boosting the device properties of all-PSCs.

Heterostructured Mo2N–Mo2C Nanoparticles Coupled with N‐Doped Carbonized Wood to Accelerate the Hydrogen Evolution Reaction

Mo2C is a promising non‐precious hydrogen evolution reaction (HER) electrocatalyst. However, regulating the strong hydrogen adsorption characteristics of Mo2C and finding suitable support electrodes are essential processes before Mo2C can replace Pt to realize a sustainable hydrogen economy. Herein, the facile synthesis of heterostructured Mo2N–Mo2C nanoparticles on N‐doped carbonized wood (Mo2N–Mo2C/N‐CW) as a self‐supported electrode through carbonization and NH3 plasma treatment is demonstrated. The synergistic effects of heterostructured Mo2N–Mo2C and N‐CW with aligned microchannels provide enhanced catalytic activity, fast charge transfer kinetics, additional active site exposure, and rapid transport of the electrolyte and H2 bubbles, which improves the HER performance. Consequently, the Mo2N–Mo2C/N‐CW electrode exhibits superior HER performance with low overpotentials of only 79 and 311 mV to reach 10 and 500 mA cm−2 in an acidic solution, respectively. It also exhibits long‐term stability for 20 h in the high‐current‐density region (110 mA cm−2). The density functional theory (DFT) calculations at various sites reveal that the heterointerface of Mo2N and Mo2C promoted the catalytic activity by optimizing the adsorption/desorption of hydrogen.

Unveiling the effect and correlative mechanism of series-dilute electrolytes on lithium metal anodes

An emerging development direction for electrolytes is the utilization of low-concentration electrolytes (LCE, generally less than 0.5 M) owing to their promising properties such as better wetting ability, reduced costs, and fast electrochemical kinetics, which have been studied in several battery scenarios. However, the direct assessment of LCEs with Li metal anodes has not yet been done, which would provide new insights to high-energy-density rechargeable lithium metal batteries (LMBs). For this purpose, apparent cycling performances of Li metal anode (LMA) in series-diluted (0.1∼1.0 M) ether-based electrolytes are reported in this study with Li||Li and Li||Cu cells, showing the enhanced performances with the concentration increasing. Moreover, the concentration effect and the underlying mechanism are revealed in detail by using coordinated post-mortem analyses and theoretical simulations, demonstrating that the preferential solvent decomposition in LCEs induces the organic-dominant interfacial layer on LMAs. Such layer demonstrates low interface stability, causing poor cycling performance among various current densities in Li half cells. However, comprehensive results also indicate that LCEs are facing a good opportunity because of the fast interfacial charge transfer kinetics originating from the weak solvation nature. This work elucidates the roles of electrolyte concentration on the LMA and uncovers their correlative mechanism of series-diluted electrolytes. It is a certain breakthrough for this timely research to provide a comprehensive perspective for designing novel low-concentration electrolytes.

Tuning Li Nucleation by a Hybrid Lithiophilic Protective Layer for High-Performance Lithium Metal Batteries

Lithium (Li) metal has been recognized as the most promising anode material for next-generation rechargeable batteries. However, the practical application of Li anodes is hampered by the growth of Li dendrites. To address this issue, a robust and uniform Sb-based hybrid lithiophilic protective layer is designed and built by a facile in situ surface reaction approach. As evidenced theoretically and experimentally, the as-prepared hybrid protective layer provides outstanding wettability and fast charge-transfer kinetics. Moreover, the lithiophilic Sb embedded in the protective layer provides a rich site for Li nucleation, which effectively reduces the overpotential and induces uniform Li deposition. Consequently, the symmetric cell exhibits a long lifespan of over 1600 h at 1 mA cm-2 and 1 mAh cm-2 with a low voltage polarization. Furthermore, excellent cycling stability is also obtained in Li-S full cells (60% capacity retention in 800 cycles at 1 C) and Li||LFP full cells (74% capacity retention in 500 cycles at 5 C). This work proposed a facile but efficient strategy to stabilize the Li metal anode.

Self-supported system of MoO2@Ni2P heterostructures as an efficient electrocatalyst for hydrogen evolution reactions in alkaline media.

Efficient, stable and low-cost catalysts are essential for improving the efficiency of hydrogen evolution reactions. Herein, the MoO2@Ni2P heterostructure electrocatalyst was synthesized in a self-supported system on a carbon paper (CP) by two-step deposition and phosphorization at low temperature. The self-supported nanoarray structure makes the catalyst to effectively and efficiently transfer electrons and exposes more of its active sites. Moreover, the strong interaction between Ni2P and MoO2 helps to effectively optimize the electronic structure. The density of states calculations demonstrate that there is an increase in the density of electronic states near the MoO2/Ni2P Fermi level. This shows that MoO2/Ni2P has fast charge transfer kinetics. MoO2 modulates the d-band center of nickel, resulting in moderate adsorption/desorption of hydrogen. The above results show that MoO2@Ni2P has good hydrogen evolution activity. The experimental results show that the overpotential (η10) of MoO2@Ni2P/CP in the alkaline environment is only 57mV with a Tafel slope of 61mV dec-1. It is similar to the commercial noble-metal catalysts and outperforms most reported catalysts.

A layered CoSeO3 pre-catalyst for electrocatalytic water oxidation.

In electrocatalytic water oxidation, the surface reconstruction of electrocatalysts is a common issue due to the applied anodic potential. The study of the fundamentals of catalyst structure transformation and the relationship between structure and performance is important. Herein, we designed two cobalt selenites (CoSeO3 and CoSeO3·2H2O) with different structures for comparative studies. The cross channels in layered CoSeO3 provide space for easy surface reconstruction. The reasons are defined by a series of electrochemical studies, indicating a larger ion diffusion coefficient, more surface contacting OH- anions and faster charge transfer kinetics in CoSeO3. This work provided a paradigm for studying the influence of geometric structure on pre-catalyst reconstruction.

Solvent Molecule Design Enables Excellent Charge Transfer Kinetics for a Magnesium Metal Anode

Lacking of suitable electrolytes is a fatal obstacle for the development of rechargeable magnesium batteries (RMBs). Herein, according to the design of a series of solvent molecules, we find 3-methoxypropylamine possesses a middle coordination ability that can be used as an effective solvent and realize a reversible Mg anode with traditional Mg salts. Mechanism study indicates, attributed to its unique solvated structure, energy barriers in both the charge transfer process and desolvation process are extremely low, thus leading to the fast charge transfer kinetics. The relationship between solvated structures and performances is precisely revealed for the first time in RMBs. Additionally, electrolytes with amine solvents possess outstanding water-resistant properties owing to strong hydrogen bonds between amine groups and water. This work proposes a universal design principle of solvent molecules for RMBs, inspiring a new thinking of developing advanced electrolytes in the view of solvents.

Mild construction of an Fe-B-O based flexible electrode toward highly efficient alkaline simulated seawater splitting

It is essential to construct self-supporting electrodes based on earth-abundant iron borides in a mild and economical manner for grid-scale hydrogen production. Herein, a series of highly efficient, flexible, robust, and scalable Fe-B-O@FeBx modified on hydrophilic cloth (denoted as Fe-B-O@FeBx/HC, 10 cm × 10 cm) are fabricated by mild electroless plating. The overpotentials and Tafel slope values for the hydrogen and oxygen evolution reactions are 59 mV and 57.62 mV dec−1 and 181 mV and 65.44 mV dec−1, respectively; only 1.462 V is required to achieve 10 mA cm−2 during overall water splitting (OWS). Fe-B-O@FeBx/HC maintains its high catalytic activity for more than 7 days at an industrial current density (400 mA cm−2), owing to the loosened popcorn-like Fe-B-O@FeBx that is firmly loaded on a 2D-layered and mechanically robust substrate along with its fast charge and mass transfer kinetics. The chimney effect of core–shell borides@(oxyhydro)oxides enhances the OWS performance and protects the inner metal borides from further corrosion. Moreover, the flexible Fe-B-O@FeBx/HC electrode has a low cost for grid-scale hydrogen production ($2.97 kg−1). The proposed strategy lays a solid foundation for universal preparation, large-scale hydrogen production and practical applications thereof.

Fast Ion Transport in Li‐Rich Alloy Anode for High‐Energy‐Density All Solid‐State Lithium Metal Batteries

AbstractAll‐solid‐state Li batteries (ASSLBs) with solid‐polymer electrolytes are considered promising battery systems to achieve improved safety and high energy density. However, Li dendrite formation at the Li anode under high charging current density/capacity has limited their development. To tackle the issue, Li‐metal alloying has been proposed as an alternative strategy to suppress Li dendrite growth in ASSLBs. One drawback of alloying is the relatively lower operating cell voltages, which will inevitably lower energy density compared to cells with pure Li anode. Herein, a Li‐rich Li13In3 alloy electrode (LiRLIA) is proposed, where the Li13In3 alloy scaffold guides Li nucleation and hinders Li dendrite formation. Meanwhile, the free Li can recover Li's potential and facilitate fast charge transfer kinetics to realize high‐energy‐density ASSLBs. Benefitting from the stronger adsorption energy and lower diffusion energy barrier of Li on a Li13In3 substrate, Li prefers to deposit in the 3D Li13In3 scaffold selectively. Therefore, the Li–Li symmetric cell constructed with LiRLIA can operate at a high current density/capacity of 5 mA cm−2/5 mAh cm−2 for almost 1000 h.

Highly dispersed Pt/CuO nanoclusters in N-doped porous carbon array for superior hydrogen evolution

The preparation of hydrogen evolution reaction (HER) catalysts with high activity, good stability and low precious metal loading has been the focus of research. Herein, we successfully fabricated Pt/CuO nanoclusters loaded directionally on nitrogen-doped porous carbon array using MOF as precursor. DFT calculations show that Pt sites of Pt/CuO reduced hydrogen adsorption Gibbs free energy and had a higher carrier concentration, suggesting that the Pt/CuO catalyst had faster charge transfer kinetics. In particular, the optimal electrocatalyst presented excellent catalytic performance of HER with overpotential of 39 mV at 10 mA cm−2 that was better than commercial Pt/C in alkaline electrolyte and Tafel slope of 41.7 mV·dec–1.