Fast Electron Transfer Process Research Articles

Selective lithium extraction with LiMn2O4: Impossible triangle and reconcile via in-situ growth on flexible 3D substrate

The electrochemically switched ion exchange (ESIX) with LiMn2O4, which can selectively extract lithium from salt-lake brines, has attracted intensive attention in recent years owing to the rapid development of the electric vehicle industry. However, the balancing of the membrane electrode’s impossible triangle, i.e., high load capacity, high porosity, and high conductivity, is something that has long puzzled scientists. In this study, one-step in-situ hydrothermal synthesis was utilized to prepare LiMn2O4 one-dimensional nano-rod (ODNR, 10 ∼ 40 nm and a length-diameter ratio of 18–220) on the flexible carbon cloth substrate (LiMn2O4@CC), thus reconciling the impossible triangle. The exchange capacity (37.73 mg/g), dissolution ratio (<0.05 %), kinetics (88 % capacity with 1.5 h), and specific energy consumption (5.04 Wh/mol·Li) of ODNR LiMn2O4@CC flexible electrode are significantly superior to the LiMn2O4 on rigid titanium electrode (LiMn2O4@RTE) ascribing to the 3 times higher conductivity, 2 to 4 orders of magnitude higher internal Li+ diffusion coefficient, and the intrinsic 3D porous nature of the flexible electrode. Electrochemical analyses verified the redox of ODNR LiMn2O4/λ-MnO2 is a one-electron transfer electrochemical reversible process with a fast electron transfer process, which may be induced by the in-situ growth ODNR and the 3D porous structure of the flexible substrate. The separation coefficients for Li+/Mg2+ and Li+/Na+ were 804.6 and 513.2, respectively. And the capacity retention ratio is > 92 % even after 50 cycles. This work sheds light on the reconciling of the impossible triangle for membrane electrode fabrication.

Electromagnetic Field Drives the Bioelectrocatalysis of γ-Fe2O3-Coated Shewanella putrefaciens CN32 to Boost Extracellular Electron Transfer.

The microbial hybrid system modified by magnetic nanomaterials can enhance the interfacial electron transfer and energy conversion under the stimulation of a magnetic field. However, the bioelectrocatalytic performance of a hybrid system still needs to be improved, and the mechanism of magnetic field-induced bioelectrocatalytic enhancements is still unclear. In this work, γ-Fe2O3 magnetic nanoparticles were coated on a Shewanella putrefaciens CN32 cell surface and followed by placing in an electromagnetic field. The results showed that the electromagnetic field can greatly boost the extracellular electron transfer, and the oxidation peak current of CN32@γ-Fe2O3 increased to 2.24 times under an electromagnetic field. The enhancement mechanism is mainly due to the fact that the surface modified microorganism provides an elevated contact area for the high microbial catalytic activity of the outer cell membrane's cytochrome, while the magnetic nanoparticles provide a networked interface between the cytoplasm and the outer membrane for boosting the fast multidimensional electron transport path in the magnetic field. This work sheds fresh scientific light on the rational design of magnetic-field-coupled electroactive microorganisms and the fundamentals of an optimal interfacial structure for a fast electron transfer process toward an efficient bioenergy conversion.

Revisiting the Butler-Volmer Electrode Kinetics: Separating the Anodic and Cathodic Current Components of a Quasi-Reversible Electrode Reaction in Staircase Voltammetry

A simple mathematical strategy is proposed to estimate anodic and cathodic current components in voltammetry by combining the basic mathematical model of a quasi-reversible electrode reaction at a conventional planar electrode with the Butler-Volmer electrode kinetics with a goal to simplify and facilitate the measurement of electrode kinetics. In spite of the fact that the separate anodic and cathodic current components are experimentally inaccessible parameters, it is demonstrated for the first time that they can be reliably estimated from the net (total) current over the whole potential interval of a common voltammetry, requiring only the current–potential relationship, without prior knowledge of any electrode kinetic parameter (i.e., the standard rate constant and the electron transfer coefficient). The mathematical procedure requires semi-integration of the current and previous knowledge of the formal potential of the studied redox couple. The theory predicts that very fast electrode processes, with an apparent electrochemical reversible behavior, are associated with anodic and cathodic current components the intensity of which is proportional to the standard rate constant. Thus, the proposed simple methodology provides a new perspective in analyzing voltammetric data and expands the accessible kinetic interval towards very fast electron transfer processes by means of simple voltammetry at macroscopic planar electrodes. The proposed methodology is experimentally illustrated with the electrode reaction of hexacyanoferrate(II) ion oxidation at platinum electrode.

CuTe supported on graphitic carbon nitride nanocomposite as an effective electrocatalyst for oxidation of water in basic media

For the purpose of using water electrolysis to yield hydrogen and to solve this issue of energy shortage, the highly active electrocatalysts for water (H2O) oxidation must be developed. For this purpose, the potential of copper-based nanomaterials electrocatalysts are completely investigated due to its good conductivity. In this study, we account the hydrothermal synthesis of novel hierarchical CuTe-gCN nanocomposite, and numerous characterization techniques are utilized to check the crystal structure, morphology, textual properties and oxidation states as well. On the other hand, the electrocatalytic performance and durability for OER in basic conditions are confirmed by different electrochemical testing. Furthermore, among all the CuTe-gCN nano-catalyst have exceptional electrocatalytic performance, like, a less overpotential around 277 mV, that is less than 312 and 326 mV for CuTe and gCN, respectively to get a current density (Cd) around 10 mAcm−2. On the other hand, it is also showing results almost similar to RuO2 having overpotential of 269 mV as well. In addition, the as prepared CuTe-gCN nanohybrid shows an impressively smaller Tafel value of 53 mVdec-1 to show the fast electron transfer process. Hence, the remarkable results are because of large surface area, accessible mesoporous structure, the remarkable electrical conductivity of gCN shows synergistic effect with CuTe was responsible for high catalytic performance, and may be useful for many other applications in future.

Enhanced Photovoltaic Property and Panchromatic Photocatalytic by Forming D‐π‐A‐Bacteriochlorin Dyads: A Computational Investigation

The photovoltaic characteristics and panchromatic photocatalysis based on monomers and bithiophene‐chlorophyll dyads is investigated. The optical properties and the electron transport capacity of the titled dyes are explicated by investigating the geometry, electronic structure, electron injection, and recombination, intramolecular charge transfer, regeneration process, dye aggregation, and light‐harvesting. The results manifest that the original 3,3′‐dithioalkyl‐2,2′‐bithiophene (SBT)‐based molecule behaves better with photovoltaic performance and an enhanced JSC and VOC. For molecular design, the designed dyads not only show the enhanced absorption range and prolonged excited lifetimes but also noticeable electron transfer ability. Moreover, the strong interfacial interaction, fast electron transfer process, long recombination distance, inhibition in dye aggregate, enhanced regenerative interaction energy are elucidated, which is beneficial for a better photocurrent response. However, the slight shift of the conduction band edge in dyads significantly reduces the VOC, especially for SBT‐Chl. Among dyads, SBT‐BChl exhibits outstanding photovoltaic performance of 14%. Besides, photocatalysis analysis manifests that the dyad composites behave with red‐shifted spectra, enhanced dipole moments, better interfacial interaction to ensure electron transfer, which significantly improved the photocatalytic performance of TiO2. Our study is expected to offer theoretical guidelines for further screening the promising D‐π‐A‐bacteriochlorin dyads in photoelectric functional materials.

Optical Properties of Cationic Perylenediimide Nanowires in Aqueous Medium: Experimental and Computational Studies

Cationic perylenediimide derivative, namely N,N’-di(2-(trimethylammoniumiodide)ethylene) perylenediimide (TAIPDI), has been synthesized and characterized in an aqueous medium by using dynamic light scattering (DLS), X-ray diffraction (XRD), fourier-transform infrared (FTIR), scanning electron microscope (SEM), and high-resolution transmission electron microscopy (HRTEM) techniques. The optical absorption and fluorescence spectra of TAIPDI revealed the formation of aggregated TAIPDI nanowires in water, but not in organic solvents. In order to control the aggregation behavior, the optical properties of TAIPDI have been examined in different aqueous media, namely cetyltrimethylammonium bromide (CTAB), and sodium dodecyl sulfate (SDS). Furthermore, the utilization of the examined TAIPDI for constructing supramolecular donor–acceptor dyad has been achieved by combining the electron accepting TAIPDI with the electron donating 4,4’–bis (2-sulfostyryl)-biphenyl disodium salt (BSSBP). The formed supramolecular dyad TAIPDI-BSSBP through the ionic and electrostatic π-π interactions have been well examined by various spectroscopic techniques, e.g., steady-state absorption and fluorescence, cyclic voltammetry, and time-correlated single-photon counting (TCSPC), and first principle computational chemistry methods. Experimental results suggested the occurring of intra-supramolecular electron transfer from BSSBP to TAIPDI with rate constant and efficiency of 4.76 × 109 s−1 and 0.95, respectively. The ease of construction, absorption in the UV–Visible region, and fast electron transfer process render the supramolecular TAIPDI-BSSBP complex as a donor–acceptor material for optoelectronic devices.

High-Spatiotemporal-Resolution Electrochemical Measurements of Electrocatalytic Reactivity

The real-time measurement of the individual or local electrocatalytic reactivity of catalyst particles instead of ensemble behavior is considerably challenging but very critical to uncover fundamental insights into catalytic mechanisms. Recent remarkable efforts have been made to the development of high-spatiotemporal-resolution electrochemical techniques, which allow the imaging of the topography and reactivity of fast electron-transfer processes at the nanoscale. This Perspective summarizes emerging powerful electrochemical measurement techniques for studying various electrocatalytic reactions on different types of catalysts. Principles of scanning electrochemical microscopy, scanning electrochemical cell microscopy, single-entity measurement, and molecular probing technique have been discussed for the purpose of measuring important parameters in electrocatalysis. We further demonstrate recent advances in these techniques that reveal quantitative information about the thermodynamic and kinetic properties of catalysts for various electrocatalytic reactions associated with our perspectives. Future research on the next-generation electrochemical techniques is anticipated to be focused on the development of instrumentation, correlative multimodal techniques, and new applications, thus enabling new opportunities for elucidating structure-reactivity relationships and dynamic information at the single active-site level.

Zeolitic imidazolate framework-67 derived Al-Co-S hierarchical sheets bridged by nitrogen-doped graphene: Incorporation of PANI derived carbon nanorods for solid-state asymmetric supercapacitors

Metal sulfides have been widely enticed as battery-type electrodes in supercapacitor devices because of their maximal theoretical capacitance. Nevertheless, their lower conductivity and ion transport kinetics can largely restrict their rate performance, hence the practical usage in fields of demanding high power devices. Therefore, the design of new electrodes with higher energy and power densities remains a highly challenging task. To the best of our knowledge, a novel hierarchical composite of Al-CoS2 on nitrogen-doped graphene (NG) is prepared based on a zeolite imidazole framework using a simple and scalable hydrothermal process. In this hybrid, ultrathin Al-CoS2 nanosheet arrays are vertically orientated on the NG framework to limit self-aggregation, hence increasing the electrical property and cycle stability of composite. It is investigated that the Al/Co feeding ratio plays a crucial role in controlling the obtained hierarchical structure of Al-Co-S sheets and their electrode performance. Also, Al3+ can influence remarkably the morphology and electrochemical property of the resultant graphene composite. An effective synergism is noticed between the redox Al-CoS2 and NG resulting in fast electron transfer and charging-discharging processes. Surprisingly, when the as-developed composite is utilized as a positive electrode at an applied current density of 1 A/g, a specific capacitance of 1915.8 F/g is attained with ultra-long cycle stability (96%, 10,000 cycles) and an excellent retention rate (∼89%). As a consequence, when a solid-state asymmetric supercapacitor (ASC) device is made by combining an Al-CoS2@NG hybrid with a negative electrode made of polyaniline (PANI) derived carbon nanorods (PCNRs), it demonstrates remarkable specific capacitance (188 F/g), energy density (66.9 Wh/kg), and cyclic stability of 92% after 10,000 cycles. This may open the pathway for the application of the next-generation supercapacitors in the future.

Modulating the adsorption orientation of methionine-rich laccase by tailoring the surface chemistry of single-walled carbon nanotubes

Achieving fast electron transfer process between oxidoreductase and electrodes is pivotal for the biocathode of enzymatic biofuel cells (EBFCs). However, in-depth understanding of the interplay mechanism between enzymes and electrode materials remains challenging when designing and constructing EBFCs. Herein, atomic-scale insight into the direct electron transfer (DET) behavior of Thermus thermophilus laccase (TtLac) with a special methionine-rich β-hairpin motif adsorbed on the carboxyl-functionalized carbon nanotube (COOH-CNT) and amino-functionalized carbon nanotube (NH2-CNT) surfaces were disclosed by multi-scale molecular simulations. Simulation results reveal that electrostatic modification is an effective way to tune the DET behavior for TtLac on the modified-CNTs electrode surface. Surprisingly, the positively charged TtLac can be attracted by both negatively charged COOH-CNT and positively charged NH2-CNT surfaces, yet only the latter is capable to trigger the DET process due to the ‘lying-on’ adsorption orientation. Specifically, the T1 copper site is near the methionine-rich β-hairpin motif, which is the key binding site for TtLac binding onto the NH2-CNT surface via electrostatic interaction, π−π stacking and cation−π interaction. Moreover, TtLac on the NH2-CNT surface undergoes less conformational changes than those on the COOH-CNT surface, which allows the laccase stability and catalytic efficiency to be well preserved. These findings provide a fundamental guidance for future design and fabrication of methionine-rich laccase-based EBFCs with high power output and long lifespan.

Au-Decorated N-Rich Carbon Dots as Peroxidase Mimics for the Detection of Acetylcholinesterase Activity

Well-distributed metals anchored on supports have attracted great attention owing to their potential application as cost-effective catalysts. Here, we demonstrate the successful preparation of Au-decorated N-rich carbon dot (Au-CD) nanocomposites, which possess excellent stability in aqueous media. The Au-CDs exhibit remarkable peroxidase-mimicking activity and high affinity to the substrate due to the fast electron-transfer process and ligand-free surface. Based on this, an Au-CD nanozyme-based colorimetric biosensor was successfully developed to assess the activity of acetylcholinesterase with high sensitivity and selectivity. More importantly, an ideal performance was achieved in clinical serum analysis. This work paves the way for the development of well-distributed metals anchored on supports as nanozymes for sensing applications.

Complexity of Electron Injection Dynamics and Light Soaking Effects in Efficient Dyes for Modern DSSC

Electron transfer dynamics in dye sensitized solar cells (DSSCs) employing triphenylamine Y123 dye were investigated by means of femtosecond broadband transient absorption spectroscopy in the visible and mid-IR range of detection. The electron injection process to the titania conduction band was found to appear biphasically with the time constant of the first component within 350 fs and that of the second component between 80 and 95 ps. Subsequently, the effects of continuous irradiation on the ultrafast and fast electron transfer processes were studied in the systems comprising Y123 dye or carbazole MK2 dye in combination with cobalt- or copper-based redox mediators: [Co(bpy)3](B(CN)4)2/3 (bpy = 2,2′-bipyridine) or [Cu(tmby)2](TFSI)1/2 (tmby = 4,4′,6,6′ tetramethyl-2,2′-bipyridine, TFSI = bis(trifluoromethane)sulfonamide). We have found that the steady-state illumination led to acceleration of the electron injection process due to the lowering of titania conduction band edge energy. Moreover, we have observed that the back electron transfer to the oxidized dye was suppressed. These changes in the initial (up to 3 ns) charge separation efficiency were directly correlated with the photocurrent enhancement.

One-step synthesis of γ-Fe2O3/Fe3O4 nanocomposite for sensitive electrochemical detection of hydrogen peroxide

Maghemite/magnetite nanocomposite (γ-Fe2O3/Fe3O4) was prepared via an electrochemical method using pulse alternating current and applied for electrocatalytic reduction and sensing of hydrogen peroxide. The structural and compositional analysis of the γ-Fe2O3/Fe3O4 was characterized by XRD, SEM, TEM and XPS. Its thermal decomposition behavior was studied using TG/DSC. The mechanism for γ-Fe2O3/Fe3O4 nanocomposite formation was proposed. Furthermore, the H2O2 sensing performance of the γ-Fe2O3/Fe3O4 nanocomposite was evaluated in 0.1 M KH2PO4. The sensor exhibited a fast electron transfer process in γ-Fe2O3/Fe3O4 nanocomposite. The optimized H2O2 sensor revealed a remarkable low limit of detection of 0.05 μM, a wide linear range from 0.0002 to 8 mM, and a fast response time of 2 s. These results demonstrated that γ-Fe2O3/Fe3O4 prepared via an electrochemical method using pulse alternating current is a promising efficient material for electrochemical sensing of H2O2.

Electroanalytical Performance of Graphene Paste Electrode Modified Al(III)-TiO2 Nanocomposites in Fipronil Solution

The new composite material Al(III)-TiO2 has been synthesized and applied as a modifier of graphene paste electrode for the determination of fipronil pesticide by cyclic voltammetry. The methods were to synthesis of Aluminum-Titanium dioxide (AT), preparation of graphene paste electrode with mass varied Al(III)-TiO2 (GAT) (0.05 g, 0.1 g, 0.2 g), and fipronil electroanalytic respons. Addition of Al(III)-TiO2 to the graphene paste electrode shows redox properties which are well characterized by a fast electron transfer process. Based on the results of measurements in a solution containing fipronil, it is known that fipronil is oxidized at a potential value of 0.26 V. Furthermore, the fipronil oxidation process on the GAT surface is influenced by diffusion control, this is powered by R2 value 0.91 when plotted between peak oxidation currents (Ip­a) vs. root scan rate. Other results show that measurement linearity is in the range 0.01 to 0.09 µg/L with a limit of detection (LOD) value of 0.0164 μg/L. Moreover, GAT shows good stability in the determination of fipronil with% RSD equal to 5%.

Construction of electrochemiluminescence sensing platform with in situ generated coreactant strategy for sensitive detection of prostate specific antigen

A sandwich-type ECL platform was fabricated for sensitive detection of prostate specific antigen (PSA) by using AuNPs decorated MoS2 (MoS2-AuNPs) as electrode material and SiO2 nanoparticles labeled with secondary antibody (Ab2) and glucose oxidase (Ab2-SiO2-GOD) as signal probes. Owing to the excellent conductivity and large surface area of MoS2-AuNPs, the fast electron transfer process and the immobilization of numerous biomolecules can be achieved. The GOD labeled signal probes can realize the in situ generation of H2O2 as coreactant to amplify the ECL intensity of luminol. The developed immunosensor displayed a wide linear range of 0.5 pg mL−1–10.0 ng mL−1 and low detection limit of 0.20 pg mL−1 for PSA detection. The immunosensor also has been successfully applied for the analysis of PSA in human serum samples. Furthermore, the proposed strategy shows great application prospects for determination of other biomarkers in biological samples.

Fabrication of ultra-sensitive piperidine chemical sensor with a direct grown well-aligned ZnO nanorods on FTO substrate as a working electrode

In this work, we report a direct growth of well-aligned zinc oxide nanorods (ZNRs) on fluorine doped tin oxide (FTO) substrate by a single step chemical method in an aqueous solution; the synthesized ZNRs were then used for piperidine sensing studies, as a working electrode. The ZNRs were uniformly grown in a large area, highly crystalline, and vertically aligned with an average length and diameter of ~650 nm and ~50 nm, respectively. The vertically aligned ZNRs provide the higher surface area for electrocatalytic activity of piperidine, and thus exhibited an ultra-sensitivity of 527 μAmM−1cm−2, a low detection limit (~60 nM), and a wide linear detection range from 0.1 μM to 200 μM. The improved piperidine sensing response characteristics of direct grown ZNRs on FTO substrate due to the large surface area, higher electrocatalytic activity and the fast electron transfer process, which makes them interesting candidate for fabricating other chemical sensing devices.

Non‐covalent Immobilization of Iron‐triazole (Fe(Htrz)3) Molecular Mediator in Mesoporous Silica Films for the Electrochemical Detection of Hydrogen Peroxide

AbstractMesoporous silica thin films encapsulating a molecular iron‐triazole complex, Fe(Htrz)3 (Htrz=1,2,4,‐1H‐triazole), have been generated by electrochemically assisted self‐assembly (EASA) on indium‐tin oxide (ITO) electrode. The obtained modified electrodes are characterized by well‐defined voltammetric signals corresponding to the FeII/III centers of the Fe(Htrz)3 species immobilized into the films, indicating fast electron transfer processes and stable operational stability. This is due to the presence of a high density of redox probes in the material (1.6×10−4 mol g−1 Fe(Htrz)3 in the mesoporous silica film) enabling efficient charge transport by electron hopping. The mesoporous films are uniformly deposited over the whole electrode surface and they are characterized by a thickness of 110 nm and a wormlike mesostructure directed by the template role played by Fe(Htrz)3 species in the EASA process. These species are durably immobilized in the material (they are not removed by solvent extraction). The composite mesoporous material (denoted Fe(Htrz)3@SiO2) is then used for the electrocatalytic detection of hydrogen peroxide, which can be performed by amperometry at an applied potential of −0.4 V versus Ag/AgCl and by flow injection analysis. The organic‐inorganic hybrid film electrode displays good sensitivity for H2O2 sensing over a dynamic range from 5 to 300 μM, with a detection limit estimated at 2 μM.

Selective photoluminescence enhancement of red emitted surface modified poly(p-phenylenediamine) dots: An ultra-sensitive anion photoluminescence sensor for F− in vitro

• An ultra-sensitive anion PL sensor for F − was reported. • The system’s detection limit is 2 × 10 −10 M, lower than most other methods. • This “OFF-ON” detection system shows value in practical applications. • We also show successful F − detection in vitro based on TPPDs. • This work is helpful for the development of other anion PL sensors. The weak interactions between anions and common functional groups make it difficult for the development of anion photoluminescence sensors. In this work, we report an ultra-sensitive anion photoluminescence (PL) sensor for F − based on triethylene glycol monomethyl ether modified poly(p-phenylenediamine) dots (TPPDs). Due to the PET process in excited TPPDs, no obvious PL behavior can be observed in TPPDs. Due to the fast photoinduced electron transfer (PET) process in excited TPPDs, no obvious photoluminescence behavior can be observed: however, the PET process can be cut off in the presence of F − and TPPDs show bright red PL. The detection limit of this system is 2 × 10 −10 M, which is much lower than most other reported detection methods. Compared with traditional “ON-OFF” PL sensors, such an “OFF-ON” PL detection system shows higher value in practical applications. The detection system exhibits superior photostability and high selectivity for F − . We also demonstrate the successful F − detection in vitro based on TPPDs.

Photoconductive Curved-Nanographene/Fullerene Supramolecular Heterojunctions.

This study presents synthesis and characterizations of two novel curved nanographenes that strongly bind with fullerene C60 to form photoconductive heterojunctions. Films of the self-assembled curved nanographene/fullerene complexes, which served as the photoconductive layer, generated a significant photocurrent under light irradiation. Gram-scale quantities of these curved nanographenes (TCR and HCR) as the "crown" sidewalls can be incorporated into a carbon nanoring to form molecular crowns, and the molecular structure of C60 @TCR is determined by single-crystal X-ray diffraction. The UV/Vis absorption and emission spectra, and theoretical studies revealed their unique structural features and photophysical properties. Time-resolved spectroscopic results clearly suggest fast photoinduced electron transfer process in the supramolecular heterojunctions.

Photoconductive Curved‐Nanographene/Fullerene Supramolecular Heterojunctions

AbstractThis study presents synthesis and characterizations of two novel curved nanographenes that strongly bind with fullerene C60 to form photoconductive heterojunctions. Films of the self‐assembled curved nanographene/fullerene complexes, which served as the photoconductive layer, generated a significant photocurrent under light irradiation. Gram‐scale quantities of these curved nanographenes (TCR and HCR) as the “crown” sidewalls can be incorporated into a carbon nanoring to form molecular crowns, and the molecular structure of C60@TCR is determined by single‐crystal X‐ray diffraction. The UV/Vis absorption and emission spectra, and theoretical studies revealed their unique structural features and photophysical properties. Time‐resolved spectroscopic results clearly suggest fast photoinduced electron transfer process in the supramolecular heterojunctions.

Electrochemical Hydrogenation with Gaseous Ammonia.

As a carbon-free and sustainable fuel, ammonia serves as high-energy-density hydrogen-storage material. It is important to develop new reactions able to utilize ammonia as a hydrogen source directly. Herein, we report an electrochemical hydrogenation of alkenes, alkynes, and ketones using ammonia as the hydrogen source and carbon electrodes. A variety of heterocycles and functional groups, including for example sulfide, benzyl, benzyl carbamate, and allyl carbamate were well tolerated. Fast stepwise electron transfer and proton transfer processes were proposed to account for the transformation.