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In this work we investigate the effects of the diffuse double layer thickness on the electrochemical Stark tuning and oxidation of carbon monoxide at Pt(111) surfaces in perchloric acid solution. The diffuse double layer thickness was modified by changing the concentration (ionic strength) of the supporting electrolyte. The Stark tuning slope of the adsorbed CO was evaluated with Fourier Transformed Infrared Spectroscopy, and the CO oxidation was monitored with cyclic voltammetry. The results show that both electrochemical Stark tuning and oxidation are independent of the HClO4 concentration of the supporting electrolyte, revealing the absence of diffuse layer effects on the aqueous Pt(111)/CO system. By comparison to previously reported theoretical calculations, we attribute this insensitivity to the special double layer structure of Pt(111)/CO, in which the potential drop occurs primarily between the terminating oxygen of the adsorbed CO adlayer and first water layer of the electrolyte, making the properties of adsorbed CO nearly independent of the ionic strength of the electrolyte. (c) 2018 The Authors. Published by Elsevier Ltd.

Sodium-ion batteries (SIBs) have recently been proclaimed as the frontrunner 'post lithium' energy storage technology. This is because SIBs share similar performance metrics with lithium-ion batteries, and sodium is 1000 times more abundant than lithium. In order to understand the electrochemical characteristics of SIBs and improve present-day designs, physics-based models are necessary. Herein, a physics-based, pseudo-two-dimensional (P2D) model is introduced for SIBs for the first time. The P2D SIB model is based on Na3V2(PO4)2F3 (NVPF) and hard carbon (HC) as positive and negative electrodes, respectively. Charge transfer in the NVPF and HC electrodes is described by concentration-dependent diffusion coefficients and kinetic rate constants. Parametrization of the model is based on experimental data and genetic algorithm optimization. It is shown that the model is highly accurate in predicting the discharge profiles of full cell HC//NVPF SIBs. In addition, internal battery states, such as the individual electrode potentials and concentrations, can be obtained from the model at applied currents. Several key challenges in both electrodes and the electrolyte are herein unraveled, and useful design considerations to improve the performance of SIBs are highlighted.

ZnFe 2 O 4 and M x Zn 1-x Fe 2 O 4 (M = Sn, Mg) nanorods are synthesized by a facile co-precipitation method followed by thermal treatment of metal-organic frameworks in air to form mesoporous structure. Temperatures of thermal treatment affects the porous structure of the materials and influences charge/discharge process of ZnFe 2 O 4 . From the electrochemical performance, we find that doping Sn which is electrochemically active would raise the voltage plateau corresponding to the reaction peaks of the doping elements, and Sn 0.05 Zn 0.95 Fe 2 O 4 exhibits the highest capacity of 1318 mA h g −1 after 50 cycles at 0.1 C. In contrast, doping Mg which is electrochemically inactive would inhibit volume change and stabilize structure during lithiation-delithiation. Mg 0.9 Zn 0.1 Fe 2 O 4 shows an excellent reversible capacity of 811 mA h g −1 with a capacity retention of 82% after 250 cycles at 1 C, while the pristine ZnFe 2 O 4 only remains 382 mA h g −1 with a capacity retention of 32%.

In search of an optimal gene electrotransfer (GET) protocol, an electroporation-based (EP) tumor treatment with great potential as a non-viral gene-delivery system, the concept of the dose-response relationship is introduced. It is shown that a reliable dose parameter is the pulse dosage and reliable response parameters are the reversibly electroporated tissue area as well as the unwanted damaged tissue area and plasmid damage due to pH. The standard stationary EP model consists in computing the reversibly electroporated tissue area in the first pulse as the region of tissue subjected to an electric field distribution higher than an electric field threshold for EP, where the electric field threshold comes from an experimental measurement and the electric field distribution from the solution of the nonlinear stationary Laplace equation for the electrostatic potential. The extended standard EP model introduced here consists in replicating for n consecutive pulses the standard EP model, via the experimental measurement in time of the successive thresholds. Because experimental data of this threshold variation is lacking, an exponential time decay function is assumed based on experimental measurements. The damage induced by pH fronts is defined as the tissue area subjected to pH abrupt changes above a basic threshold or below an acid threshold, where these changes come from numerical solutions via the electrolytic ablation (EA) model for EP-based protocols and the basic and acid thresholds from experiments. An optimal dose-response relationship in a GET protocol, for the range of pulse intensities with fixed pulse length and frequency, tested here, is predicted as the critical pulse dosage yielding maximum reversibly electroporated tissue area with minimal tissue area damage induced by pH fronts. Moreover, since damage induced by pH changes is proportional to the Coulomb dosage, damage induced by pH fronts is negligible in typical EP-based tumor protocols such as in electrochemotherapy (ECT) and irreversible electroporation (IRE) but not in GET, due to the most often longer pulses applied/used, i.e. higher dosage applied.

To address the demand for high-rate anodes for lithium ion batteries, herein, crumpled MoS2/nitrogen-doped carbon hybrid sheets (CMNCS) were synthesized via a modified mix-bake-wash method. Material characterization proved that CMNCS comprised sheets with few-layer thickness that were composed of homogenously distributed MoS2 and N-doped carbon matrix with numerous mesopores. CMNCS offers the morphological advantage of 3D interconnected electron pathways and an enlarged ionic contact area for improving the rate performance. Furthermore, the N-doped carbon matrix in CMNCS plays a role in enhancing the electrical conductivity as well as suppressing volume changes during cycling. The CMNCS demonstrated a reversible discharge capacity of 264 mAh g−1 at 10 A g−1 and a stable cycle life with a discharge capacity of 324.2 mAh g−1 and coulombic efficiency of 99.7%, even after the 1000th cycle at 4 A g−1. These results indicate that CMNCS offers great potential as an anode material for lithium ion batteries that require high current and stable cycle life.

Hydrogen production is an immediate need to replace the fossil fuels to keep environmental balance, and water splitting is an effective solution in presence of catalyst through oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). Herein, for the first time, we have synthesized Iron Phosphate Hydroxide (Fe 2.95 (PO 4 ) 2 (OH) 2 ) thin film electrode as a superior electrocatalyst by facile hydrothermal method using binder free approach. The crystallographic properties are studied from X-ray diffraction pattern, and Reitveld refinement analysis shows best fit with the tetragonal Lipscombite structure of Iron Phosphate Hydroxide (Fe 2.95 (PO 4 ) 2 (OH) 2 ). Flower like structure consist of agglomerated nanorods on micro and sub-micrometric spheres of Fe 2.95 (PO 4 ) 2 (OH) 2 exhibits lower overpotential of 281 mV at 10 mA/cm 2 current density towards OER in alkaline (1 M KOH) medium and maintains its activity after 12 h catalytic stability test. Moreover, prepared electrode shows HER with overpotential 165.7 mV at current density 10 mA/cm 2 in acidic (1 M H 3 PO 4 ) medium and demonstrates enhanced performance (126.4 mV overpotential) after 12 h catalytic stability. The Fe 2.95 (PO 4 ) 2 (OH) 2 thin film electrodes show superior performance in OER and HER, compared with its oxide counterpart (Fe 2 O 3 ).

Here we introduce the new approach to high-efficiency power generation from a salinity difference using conventional nanoporous Nafion membrane. When access areas on each side of nanoporous Nafion membrane are set to be asymmetric, the ratio of ionic current upon a voltage bias of the different polarity also becomes asymmetric, resulting in ionic diode phenomena. When this geometrical ionic diode effect is combined with a salinity gradient, it can help significantly improve the energy conversion efficiency from a salinity difference even under a hyper-saline environment with a large salinity difference, e.g. ∼41% conversion efficiency and ∼120 nW power generation with 1 M KCl and 1000-fold salinity difference, both of which are comparable with the best performances reported in the previous studies. We propose that the decrease in ion concentration polarization at a low salt concentration side is responsible for the enhanced power generation with the membrane having asymmetric access areas. Our approach is simple to implement and can be applicable to any nanoporous membrane to enhance the power generation from a salinity difference.

The effects of catalyst support and synthesis process on the interaction between Pt nanoparticles (NPs) and S-doped carbon nanotubes (SCNTs), and the resultant electro-oxidation catalytic performance of glycerol, formic acid and CO were systematically researched. Pt NPs on SCNTs had better electro-oxidation catalytic performances than that of Pt NPs on CNTs. The doped S in thiophene-like structure (C-S-C) activated the neighboring C atoms to interact with Pt NPs, improving the catalytic performance with stronger ability to remove poisonous intermediates. The formed C-S-C had a synergistic effect with the neighboring Pt-C, promoting the adsorption and activation of reactants. The improved metal-support interaction resulted in Pt with smaller nanoparticle size and more exposed active sites. In different synthesis process, Pt NPs were more likely to interact with activated C neighboring S in ethylene glycol reduction method. However, defects containing doped S preferred to interact with Pt NPs in impregnation method. The research results indicated that rationally regulating the surface properties of carbon support and choosing an appropriate catalyst synthesis strategy to intensify the required metal-support interaction can greatly improve the catalytic performance.

Considering the lack of lithium resources, sodium- and potassium-ion storage systems possess great potential for large scale energy storage. However, the slow charge storage kinetics of graphite hinders the intercalation of large sodium and potassium ions, leading to low capacity and poor cycling stability. Herein, we report a nitrogen-doped carbon nanotube coated porous carbon derived from the metal-organic framework precursor for boosting the sodium and potassium ion storage. The carbon product tested as anode deliverers a high specific capacity of 320/339 mAh g−1 at 0.05 A g−1 in sodium/potassium ion batteries. Ex-situ X-ray diffraction studies indicate that the dominant charge storage mechanism in the carbon is based on adsorption, rather than intercalation. In addition, kinetics analysis further confirms that the capacitive-controlled capacity is dominant in the carbon electrode. To further illustrate the merits of metal-organic framework derived nanoporous materials, hybrid sodium and potassium ion capacitors are assembled by using the carbon anode and cathode both from metal organic frameworks. A high energy density of 118/126 W h kg−1 can be achieved for sodium/potassium ion capacitors. The present work provides a new strategy to design nanostructured carbons for high-performance metal-ion capacitors based on earth-abundant metals besides lithium.

Nickel-cobalt (Ni-Co) oxide nanocages were synthesized by etching the cobalt-based metal-organic framework (Co-MOF) with nickel nitrate in an isopropyl alcohol solution. The dodecahedral Co-MOF (300 nm in size) was composed of micropores, while the Ni-Co oxide nanocages gained additional mesopores and macropores. Both Co-MOF and Ni-Co oxide electrodes in KOH behaved more like the nondiffusion-controlled pseudocapacitor through the surface adsorption/desorption with a concomitant faradaic charge-transfer reaction. In the presence of ferrocyanide/ferricyanide redox electrolyte, both nondiffusion- and diffusion-controlled currents contributed equally to the current response of Ni-Co oxide electrode at lower scan rates. Nondiffusion-limited processes governed the charge-storage behavior of Ni-Co oxide electrode at faster scan rates. The Ni-Co oxide electrode with redox electrolyte showed high specific capacities of 810 and 496 C g−1 at the charge/discharge current densities of 10 and 50 A g−1, respectively, much greater than that electrode without redox electrolyte (384 and 348 C g−1). Ni-Co oxide electrode with highly porous nanocages could provide large electrolyte/electrode interface to store more charges and short pathways to expedite the transport of electron and ion, showing a noticeable increase in its electrochemical performance compared with Co-MOF electrode.

Herein, we design and prepare Ni3S2/NiCo2O4 arrays on Ni foam with core-shell flakes structure as charge-storage materials. In this synthetic strategy, NiCo2O4 flakes are firstly grown on Ni foam substrate through simple hydrothermal process, and then ultrathin Ni3S2 nanoflakes are electrodeposited into scaffold of NiCo2O4 arrays. Those nanoflakes supported with each other can form a three-dimensional porous and interconnected structure, which afford more active sites and ion transfer channels for redox reaction. As expected, Ni3S2/NiCo2O4 arrays show excellent charge-storage properties in electrochemical energy storage, including high specific capacity of 1201 C g−1 (3.46 C cm−2) at 1 mA cm−2, which far larger than those of pure NiCo2O4(572 C g−1, 0.86 C cm−2) and Ni3S2 (612 C g−1, 0.98 C cm−2). Meanwhile, Ni3S2/NiCo2O4 arrays show a good rate capability of 742 C g−1 at 60 mA cm−2. Furthermore, hybrid device is fabricated using Ni3S2/NiCo2O4 arrays (positive electrode) and graphene on Ni foam (negative electrode). This device can deliver high energy density of 47.62 Wh kg−1, indicating a good application ability of Ni3S2/NiCo2O4 arrays. The excellent charge-storage performance of Ni3S2/NiCo2O4 arrays is attributed to the core-shell structure of flakes arrays and synergistic effects of two components.

Micro-sized electrochemical energy storage device is a prospective candidate to power the miniaturized electronic devices and micro-pseudocapacitor (MPC) is a typical one with high power density and long life span. Developing a versatile architectural design with high capacity delivering in a micrometer range is paramount for remarkable MPC constructions. Here, an interdigitated graphene framework (IGF) is developed using a facile 3D printing technique to enable the customized geometries as well as the superior support of metal oxide nanostructures. With this unique design, the IGF-supported NiO nanorod heterostructured microelectrodes deliver high specific capacity of 220.2 C g−1 (400.3 F g−1). When directly assembled to quasi-solid-state symmetric MPCs, the NiO filled one exhibits a remarkable device capacity of 197.5 mC cm−2. Robust MPC cycling stabilities are also demonstrated during 10000 charge and discharge cycles. In addition to the NiO based ones, MnO2 nanosheet filled MPCs are also fabricated, where a high device capacity and a good cycling stability are also exhibited. We expect that this novel 3D-printed IGF can pave the way for constructing state-of-the-art miniaturized electrochemical energy storage devices with customized geometries.

Charge-discharge processes of supercapacitor with carbon black KJEC 600/Li in non-aqueous electrolyte: 1 M LiPF6 in a mixture of ethylene carbonate (1/3), diethyl carbonate (1/3), dimethyl carbonate (1/3) are investigated. Galvanostatic cycling was carried out in the range from 1 to 4 V with currents from 100 to 5000 mA/g of carbon black. The maximum discharge capacity of 196 F/g has been reached. The porous structure and hydrophilic-hydrophobic properties of carbon black KJEC 600 were investigated by the standard contact porosimetry method (MSCP). The following values were obtained: total specific surface area of 2500 m2/g, total porosity of 7.8 cm3/g, hydrophilic porosity of 4.9 cm3/g, hydrophobic porosity of 2.9 cm3/g. The obtained experimental dependence of the energy efficiency has a maximum (80%) at a current of 250 mA/g. Mathematical modeling of charge-discharge processes of the supercapacitor is developed with taking into account the charging of the double electric layer (EDL) and adsorption of lithium ions according to the Butler-Volmer equation and the Frumkin isotherm for the carbon electrode are taken into account. From the comparison of the calculated and measured charge-discharge curves it follows that these curves are satisfactorily consistent with each other, which indicates the correctness of the model. The density of the exchange current and the specific capacitance of the EDL refereed to the true surface found by the fitting are equal to i0,ad = 2.8 × 10−29A/сm2 and Cdl = 3.5 μF/сm2 respectively. On the basis of the developed model for different specific currents the energy efficiency dependences on the exchange current density of the adsorption reaction were calculated. Interestingly, these dependencies have a minimum. Based on the model, the profiles of the potential the surface coverage of lithium ions were also calculated.

Herein, we report a nano-cylindrical strontium titanate/N-doped graphene (SrTiO 3 /N-GNS) hybrid composite synthesized by a solvothermal method. The composite material has been explored by various physicochemical and electrochemical characterization techniques. It is found that the nano-cylindrical SrTiO 3 nanoparticles with highly crystalline mesoporous structure are consistently present in between as well as on the surface of N-GNS sheets resulted in 3-dimensional continuous structure. The electrochemical investigations reveal that SrTiO 3 /N-GNS hybrid composite displays excellent electrocatalytic behavior towards simultaneous electro-oxidation of two commonly encountered anti-allergic drugs viz. Diphenhydramine (DPH) and Bromhexine (BRO) in phosphate buffer of pH 7.0 employing adsorptive stripping differential pulse voltammetry. The new application of SrTiO 3 /N-GNS hybrid as an electrochemical sensor shows wide linear working range from 0.038 to 100.0 μM for DPH and 0.030–90.0 μM for BRO with detection limit of 2.1 and 1.9 nM respectively. Also, the developed sensor manifests adequate recoveries in synthetic pharmaceutical samples and human body fluids. These findings suggest that SrTiO 3 /N-GNS composite is and could serve as a potential candidate for highly sensitive electrochemical sensing applications.

High voltage LiNi0.5Mn1.5O4 material is a promising cathode for lithium ion battery, but the unsatisfied cycle stability hinders its further development in higher energy density battery. Amorphous terpolymer poly(butyl methacrylate-acrylonitrile-styrene) (P(BMA-AN-St)), which possesses good affinity with carbonated liquid electrolyte and high adhesion ability, is used together with traditional poly(vinylidene fluoride) (PVDF) binder to improve the cyclic performance of LiNi0.5Mn1.5O4 cathode. The retention ability of discharge capacity is 92% for Li/LiNi0.5Mn1.5O4 coin cell after 300 cycles at 1C rate when the cathode uses the co-binders of PVDF and P(BMA-AN-St) (2:1 in weight), compared with 55% capacity retention for the cathode fabricated with PVDF binder alone. From the physical and electrochemical characterizations of the cycled electrode, it is found that the introduced terpolymer enhances the liquid electrolyte uptake ability of LiNi0.5Mn1.5O4 cathode and the adhesion strength inside the particles by building a better interconnected conductive structure. Furthermore, the improved cycle stability of co-binder based cathode is contributed to the passivating layer formed by the terpolymer on the surface of LiNi0.5Mn1.5O4 particles, which effectively suppresses the decomposition of liquid electrolyte at high voltage and maintains the structural integrity of active material in the repeated intercalation/de-intercalation process.

An interdigitated capacitance immunosensing system based enzymatic biocatalytic precipitation on micro-comb electrode was designed for the sensitive detection of prostate-specific antigen (PSA) by coupling Ti3C2 MXenes with tyramine signal amplification strategy. The immunosensor was prepared by immobilizing anti-PSA capture antibody on MXenes-coated interdigitated electrode, whereas gold nanoparticles heavily functionalized with horseradish peroxidase (HRP) and detection antibody were utilized as the signal-transducer tags. Introduction of interdigitated electrode was expected to enhance the sensitivity of capacitance immunosensor. This system mainly consisted of the sandwich-type immunoreaction, formation of tyramine-HRP repeats on gold nanoparticle and enzymatic biocatalytic precipitation. The concatenated HRP through the tyramine oxidized numerous 4-chloro-1-naphthol molecules into insoluble benzo-4-chlorohexadienone with the help of H2O2, and coated the modified immunosensor to keep free ions away from the electrode, thus causing the local alteration in the capacitance. Under optimum conditions, the change of the immunosensor in the capacitance increased with the increasing target PSA concentrations from 0.1 ng mL−1 to 50 ng mL−1 at a detection limit of 0.031 ng mL−1. Moreover, the interdigitated capacitance immunosensor showed good reproducibility, high specificity and acceptable accuracy for the analysis of human serum specimens in comparison with those obtained from commercial human PSA ELISA kit. Importantly, Ti3C2 MXenes-based interdigitated capacitance transducer open new opportunities for protein diagnostics and biosecurity.

Developing non-precious metal bifunctional electrocatalysts for effective overall water splitting is promising to realize high-efficient renewable energy production. In this work, ternary (NixFey)2P nanoplates arrays on 3D self-supported nickel foams were prepared through a simple coelectrodeposition followed by phosphorization. The synthesized (NixFey)2P nanoplates arrays showed remarkable bifunctional electrocatalytic performances in the KOH electrolyte, with the Tafel slopes of 57.8 mV·dec−1 and 53.6 mV·dec−1, and low overpotentials of 115 mV and 182 mV to reach a current density of 10 mA cm−2 for hydrogen evolution reaction and oxygen evolution reaction, respectively. In addition, the optimized (Ni0.66Fe0.33)2P anode and cathode demonstrated outstanding ability for overall water splitting in the two-electrode alkaline electrolyzer, generating a current density of 10 mA cm−2 at the applied cell voltage of 1.61 V. This benefited by the active surface to expedite reactants absorption, faster electron transport in the solid-liquid interface and reduced charge-transfer resistance due to the bimetallic synergistic effect. This delicate design of bifunctional transition metal phosphides provides a potential approach to realize water reuse and energy regeneration by the full water splitting.

Understanding the kinetics of oxygen reduction reactions (ORRs) over non-precious-metal (NPM) catalysts in alkaline media is quite important for commercializing anion exchange membrane fuel cells. Rotating ring-disk electrode (RRDE) voltammetry has been useful for studying the selectivity of ORR, but typical analytical models might overestimate the four-electron pathway. The present study investigated ORR in alkaline media over Fe/N/C and N/C catalysts, which were prepared by pyrolyzing polyimide nano-particles. The obtained data were analyzed using the novel RRDE theory, which involves the Nabae model to distinguish a genuine four-electron reduction from a quasi-four-electron reduction (two plus two-electron reduction). The results demonstrated that the reduction with the Fe/N/C catalyst proceeded via an inherent four-electron pathway while that with the N/C catalyst prepared by a similar method proceeded majorly via a two-electron pathway.

In this study, a quasi-solid-state supercapacitor with high energy density was successfully developed using a zwitterionic gel electrolyte with a dual-function redox additive. A polyzwitterion charged polymer, poly([2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide) (PPDE), was used with LiCl as the flexible gel electrolyte. This proposed electrolyte demonstrates promise for use in practical supercapacitors due to its environmental friendliness, transparency, flexibility, and high ionic conductivity. To further improve the electrochemical performance, a dual-function redox additive, ethyl viologen dibromide, was incorporated into the polyzwitterion. With the redox mediator in the polyzwitterionic electrolyte (PPDE-LiCl-EV), the specific capacitance improved by a factor of three compared to the pristine zwitterionic polymer (178 F g−1 for PPDE-LiCl and 677 F g−1 for PPDE-LiCl-EV) due to additional faradaic reactions. In addition, a quasi-solid-state supercapacitor incorporating PPDE-LiCl-EV exhibited a high energy density of 542 Wh kg−1 and a power density of 2.88 kW kg−1 over a wide potential window of 2.4 V. Fourier transform infrared spectroscopy in attenuated total reflectance mode was employed for in situ monitoring of the redox reactions of additives on the electrode surface. To the best of our knowledge, this is the first attempt to analyze the redox reactions of redox additives.

A new core-shell structured MnO2@Ni2P2O7 (NPO) nanohybrid with unique nano-design is engineered by simple solution process and utilized as promising positive electrode for solid-state hybrid supercapacitors (HSCs). Firstly, two-dimensional (2D) NPO micro-sheets are grown on the Ni foam where the ultrathin MnO2 nanoflakes are decorated on NPO micro-sheets to realise MnO2@NPO core-shell nanohybrid. The as-synthesized MnO2@NPO electrode delivers impressive electrochemical performances with specific capacity of 309 mA h/g with long-term cycling stability over the 12,000 charge-discharge cycles. A solid-state hybrid supercapacitor (HSC) is fabricated using MnO2@NPO and activated carbon (AC) as positive and negative electrodes with polymer-gel electrolyte. The assembled HSC offers an upgraded cell potential of 1.6 V with high specific energy of 66 Wh/kg at specific power of 640 W/kg. More importantly, the HSC delivers excellent cycling stability over the 10,000 cycles (∼93% of capacity retention) with good energy efficiency at all current densities.

Rechargeable Li–CO 2 batteries recently have gained an increasing popularity because they can directly reduce fossil fuel consumption and convert chemical energy of greenhouse gas CO 2 into electric energy. However, Li–CO 2 batteries still suffer from great challenges to realize long-term cycling due to a high charging voltage to drive the electrochemical decomposition of discharge products Li 2 CO 3 . Herein, porous NiO nanofibers obtained by electrospining technique are firstly served as a high-efficient cathode catalyst in Li–CO 2 batteries. The addition of NiO not only improves the catalytic performance of batteries but also tailors the cathode structure. Experimental results and theoretical calculation show the existence of NiO facilitates a conformal growth of Li 2 CO 3 on the NiO surface with large contact areas, which promotes the decomposition of Li 2 CO 3 among charging process. Owing to these synchronous advantages, enhanced electrochemical performances including high capacity, superior round-trip efficiency and especially the long cycling-life are achieved.

In this study we investigate how electronic properties of buried semiconductor/ionic liquid interfaces may influence on charging effects observed by X-ray photoelectron spectroscopy (XPS). Droplets of the ionic liquid 1-ethyl-3-methylimidazolium bis (trifluoromethylsulfonyl)imide ([EMIM][Tf2N]) were deposited on silicon and germanium semiconductor surfaces with different doping states. Core level spectra were recorded from the ionic liquid/ultra-high vacuum interface with and without irradiation of the droplets using low energy electrons from a flood gun. Changing electron intensity results in shifts of the binding energy of all XPS signals to lower values. Magnitude of shifts is found to directly depend on the intensity of the electron beam and to correlate with the nominal resistivity of the substrates. The observations are qualitatively explained by flood gun induced changes of the electronic properties of the [EMIM][Tf2N]/substrate interface and suggested to refer to space charge layer effects.

Magnesium-1,4-benzenedicarboxylic acid (Mg-TPA) and magnesium- 1,3,5-benzene tricarboxylic acid (Mg-TMA) MOFs were synthesized and successfully incorporated in a poly (ethylene oxide) (PEO) matrix as filler for different proportions of LiN(CF3SO2)2 (LiTFSI) as salt. The membranes prepared were thermally stable up to 360 °C. The ionic conductivity of the polymer electrolytes was enhanced upon addition of MOF and a maximum conductivity of 7.02 × 10−4 S cm−1 was achieved for CPE containing 10 wt % of Mg-TPA as filler. The interfacial properties of the CPEs with lithium metal anode were analysed by compatibility, Fourier transform infrared (FT-IR) and XPS analyses. Li/NCPE/Li symmetric cells were assembled and the dendrite growth was also studied. The lithium transference numbers (t Li+) was measured as 0.58 and 0.52 for the CPE containing Mg-TPA and Mg-TMA, respectively which is appreciable for battery applications. The influence of different organic ligands on the electrochemical and interfacial properties of solid polymer electrolytes was investigated and discussed.

Scanning electron microscopy (SEM) for the electrode reaction in next-generation battery with ionic liquid (IL) electrolyte, which has both high stability under vacuum and an antistatic nature, is applied to the binder-free high capacity Si anode to observe the morphology change of the Si nanoparticle aggregate active material at different potentials during charge-discharge processes. In the IL electrolyte, 1-ethyl-3-methylimidazolium bis(fluoromethylsulfonyl)amide ([C2mim][FSA]) with 1.0 M lithium bis(trifluoromethanesulfonyl)amide (Li[TFSA]), the morphology greatly varied at the plateau observed at 0.200 to 0.070 V (vs. Li(I)/Li) in the charge-discharge curve during the first cycle, suggesting that phase transition of a-Si to c-Li13Si4 is a potential problematic process. After the first cycle, the lithiation process initiated at more positive potential. Similar behavior was also recognized in the Li[TFSA]‒tetraglyme solvate IL electrolyte in a 1:1 molar ratio ([Li(G4)][TFSA]).

The objective of this work is to explore whether carbon materials, which are usually utilized as additives for improving the electronic conductivity of oxide-based oxygen evolution reaction (OER) catalysts, could be replaced by silver nanoparticles. We integrate La 0.75 Sr 0.25 Mn 0.5 Co 0.5 O 3−δ , a perovskite with a limited electronic conductivity, in electrode compositions with either carbon materials (pyrolytic carbon of the Sibunit family – Sibunit-152, furnace black – Vulcan XC-72R, and Acetylene black) or silver nanoparticles, and investigate their OER activity in 1 M NaOH solution. We apply the rotating ring-disk electrode (RRDE) technique to separate the OER currents from those originating from corrosion of the additives under anodic polarization. We conclude that certain carbon materials would be better suited for use as conductive additives for oxide-based OER catalysts than silver particles.

Herein we provide an effective strategy for drastically improving the cyclic behavior and rate capability of an LiMn 2 O 4 (LMO) electrode at elevated temperature through P element doping. The P-doped LiMn 2 O 4 materials are characterized by X-ray diffraction, scanning electron microscopy, and X-ray photoelectron spectrometry analysis. The results show that the P element is effectively and uniformly doped within the LiMn 2 O 4 crystal lattice and is beneficial for growth of the truncated octahedral crystal structure. The electrochemical results reveal that P doping can greatly improve the cycling performance of LiMn 2 O 4 electrodes, especially improving the rate capability at elevated temperatures. At a high 10C rate of current density and 55 °C, the optimized LMO (1.5 wt% P) electrode shows the highest initial specific capacity of 101.2 mAh g −1 , which become 74.4 mAh g −1 after 500 cycles, corresponding to 73.5% capacity retention. Under similar conditions, the LMO (2.5 wt% P) electrode shows an initial discharge capacity of 78.5 mA g −1 , which become 72.2 mAh g −1 after 500 cycles, corresponding to 92.3% capacity retention.

Due to the unique three-dimensional open framework with large interstitial sites, Prussian blue analogues offer great advantages in energy storage, however, besides solid cubic or hollow structure obtained by post treatments of etching or annealing, the fine structure of Prussian blue analogues remains difficult to control by one-step method. This may somewhat hinder its full application in energy storage. Herein, for the first time, a yolk-shell K0.86Mn[Fe(CN)6]0.74·2.35H2O microboxes with self-assembled hierarchical subunits are synthesized through a facile one-step approach. This growth process utilizes the self-assembly driving force of poly-vinyl pyrrolidone (PVP) to motivate the consumption of the interior bulky crystal to outward rearrangement, and meanwhile preserving the outer shell. By virtue of the flexible reaction time, controllable structures with specific surface area and pore size can be realized. As a cathode for lithium ion battery it exhibits a high specific capacity of over 160 mAh g−1 and excellent rate performance, owing to the tailored high specific surface area yolk-shell structures. The nano-structured shell and the porous voids provide large active surface to build up the electrolyte/electrode interface and enable fast kinetics for reversible Li+ insertion and removal. With the help of highly reversible phase transition and sufficient expansion space for discharge/charge, the cathodes show an impressive cycling lifespan of 500 with over 80% capacity retention. This work highlights new insights into the rational design of Prussian blue analogues for rechargeable batteries.

Simultaneously modulating the optical and electrical properties of the hole transporting layer (HTL) plays a vital role in the performance of p-i-n perovskite solar cells (PSCs). Here, a negligible hysteresis inverted planar PSC with 17.30% power conversion efficiency was successfully fabricated by employing a thin and non-stoichiometric dopant-free nickel oxide (DF-NiOx) film as the HTL. The DF-NiOx film was formed by a radio frequency magnetron sputtering method. The Ni3+ content as well as the crystallization of the DF-NiOx thin films were tuned by regulating the post-annealing treatment, leading to enhanced optical transmittance and electrical conductivity. The optimized DF-NiOx films exhibit a high transmittance of more than 90%, appropriate conductivity, uniform surface morphology, and a better energy level match with the perovskite layer. This study not only highlights the importance of optimizing the Ni3+ content and crystallization for the formation of high-performance DF-NiOx HTLs, but also provides an excellent device platform for making large area high-performance PSCs and tandem solar cells.

Nanohybrid photoanodes made of mixed phase TiO2 nanorods (NRs) decorated with reduced graphene oxide (rGO) is fabricated by one step hydrothermal technique. Addition of rGO influences the phase formation of the TiO2 and optimum mixed phase formation of rutile (16%) and anatase (84%) TiO2 polymorphs is achieved at 1.0 wt% rGO decoration. Using rGO decorated TiO2 hybrid photoanodes, bacteriorhodopsin sensitized solar cells is fabricated with liquid and quasi-state electrolyte. Decoration of 1.0 wt% rGO upon TiO2 NRs boosted the photocurrent (Jsc = 2.2 mA/cm2) generation and photoconversion (η = 1.3%) efficiency which is 94% enhanced than pristine TiO2 NRs photoanodes. Experimental observation showcase higher rGO decoration (>1.0 wt% rGO) suppress the charge transport due to the formation of self-induced trapping sites within the transfer network. Minimum charge transfer resistance and maximum charge collection efficiency of ∼98% is achieved at 1.0 wt% rGO decorated TiO2 nanorods photoanodes. The ideal decoration of rGO (1.0 wt%) in photoanodes significantly improves the bio-sensitizer loading, charge transfer, electron lifetime and reduces the recombination of the BSSCs. Thus nanohybrid (rGO-TiO2 NR) photoanode assembled BSSC exhibit higher photoconversion efficiency than earlier BSSCs fabricated with nanoparticle (P25 mixed-phase TiO2) and nanorod (rutile and anatase pristine TiO2) based photoanodes.

Two-step aluminium anodizing is widely used to prepare oxide films with a highly-ordered porous structure through the whole thickness. It can be realized solely at relatively low values of current density in the kinetic anodizing regime that makes this process extremely time-consuming. Temperature is an important thermodynamic parameter which is able to accelerate chemical reactions and mass-transport and, thus, could be suggested as an effective tool to control the growth rate of anodic alumina. Here we report a systematic study of the porous anodic alumina films formation in 0.3 M oxalic acid electrolyte in a wide temperature range. The influence of electrolyte temperature on the kinetics of aluminium anodizing and on the morphology of the obtained anodic alumina films is addressed quantitatively. Current transients registered at various temperatures are used for the calculation of the apparent activation energy of the anodization process in both mild and hard anodizing regimes. In the case of thick oxide films and high electrolyte temperature, the increase in diffusion current contribution leads to switching the kinetically controlled anodizing to the mixed regime which results in destroying the hexagonal pore ordering. Based on the experimental findings, rational electrolyte temperatures and porous layer thicknesses for the first and second anodizing steps are proposed as a guide for express preparation of alumina films with well-ordered porous structure.

Pyrolysis gradually becomes a promising green method to dispose the sewage sludge who has brought serious problems to environment. In this study, hierarchical porous hollow carbon nanospheres are directly obtained by specific carbonization/activation procedures using sewage sludge as the only precursor for the first time. The resultant carbon possesses tailor-made hierarchically porous structure with larger surface area (1518.40 m2 g−1), high pore volume (1.21 cm3 g−1), and rich oxygenic functional groups, which is favorable for lithium ion diffusion and can better enhance the ionic conductivity in an electrode system. As anode for li-ion battery, the carbon displays superior discharge capacity, which reaches 1168.9 mAh g−1 at 0.1 A g−1 and 287.1 mAh g−1 at 2 A g−1. And the capacitance retention is 98.7% over 100 cycles at 0.1 A g−1. Therefore, it is anticipated that such a pollutants-derived carbon can facilitate the development of new green and sustainable pathways for the construction and design of well-defined porous carbon nanospheres to ease energy and environmental issues.

A novel NiCo2O4/N-doped carbon nanowebs serving as a bifunctional electrocatalyst, consisting of hollow NiCo2O4 nanospheres and N-doped carbon nanowebs are prepared through a liquid-phase synthesis method accompanied by subsequent heat treatment. The N-doped carbon nanowebs mainly contribute to the high activity for oxygen reduction reaction, whereas the NiCo2O4 nanospheres act as an active phase for oxygen evolution reaction. The electrocatalytic performance is promoted by the synergistic effect between NiCo2O4 and N-doped carbon nanowebs. Benefiting from the hollow and N-doped structure with merits of more activity sites, fast charge and mass transport, the NiCo2O4/N-doped carbon nanowebs exhibit an excellent bifunctional catalytic activity, high selectivity of the apparent 4e− pathway, small ΔE values and long-term durability. Rechargeable Zn-air batteries using NiCo2O4/N-doped carbon nanowebs as catalyst display a lower overpotential, a high capacity (826.9 mAh g−1), a high energy density (954.2 Wh Kg−1) and long-term stability (600 cycles at 5 mA cm−2), when compared to commercial Pt/C + Ir/C. Furthermore, the NiCo2O4/N-doped carbon nanowebs is directly used as air catalyst in flexible Zn-air batteries, which also exhibit superior flexibility and cycling stability. This work provide a new method for developing highly efficiency electrocatalyst, rechargeable and flexible Zn-air batteries.

Nickel (oxy)hydroxide materials gradients were prepared using bipolar electrochemistry. A correlated microscopy approach, using scanning electron microscopy and scanning electrochemical cell microscopy, was used to study the local morphology and electrocatalytic activity of the nickel (oxy)hydroxide materials gradient. It was found that bipolar electrodeposition led to the formation of discrete nickel (oxy)hydroxide particles, while energy dispersive X-ray spectroscopy and local electrochemical surface area measurements showed that the amount of nickel on the surface increased with increasing deposition overpotential. An apparent turnover frequency was calculated for the oxygen evolution reaction as a function of electrode position enabling local electrocatalytic activity to be quantified. This new approach, combining bipolar electrochemistry with local electrochemical measurements, enables the screening of electrocatalytic materials gradients generated across the surface of heterogeneous bipolar electrode substrates.

Electrodialysis (ED) is a well-established water desalination technology, applied mainly to brackish water desalination. In ED, desalination is driven by an applied electric field, which results in salt ion electromigration through alternating cation and anion exchange membranes. Recently, classical ED cells have been modified by driving them via spontaneous redox reactions occurring at the electrodes. Such a cell is distinct from classical ED as it does not require electricity, but rather requires solely chemical energy input in the form of redox active chemicals, and outputs both desalted water and electricity simultaneously. We here extend ED theory in order to capture a cell driven by spontaneous redox half-reactions occurring at electrode surfaces. In the cell considered, an AEM and CEM are separated by a channel with flowing feedwater. On the opposite side of the AEM is an anode and flowing anolyte, while a cathode and flowing catholyte are on the opposite side of the CEM. To capture cell behavior and performance at steady state, we solve a set of equations comprising the species’ Nernst–Planck equation and electroneutrality, which are coupled to activation and concentration overpotential losses at planar electrodes. Our model captures the crossover of coion species through membranes as well as electric potential, counterion, and coion concentration variations within the membranes. We elucidate key predicted phenomena, including that the cell current is limited by reactant starvation at the cathode, and that current and certain ion fluxes scale as x−1/3, where x is the coordinate in the direction of flow. Our model predicts that at steady state, the cell can achieve an order of magnitude reduction in the NaCl concentration of a 500 mM feed, while generating up to ∼42 mW/cm2 electrical power density. Further, we determined that the main limitation of the cell as designed is a relatively high coion crossover flux through the membranes.

Confining the dissolution and diffusion of polysulfide is considered a key factor in the realization of high-performance lithium-sulfur battery. Here, we report a polydopamine (pDA) coated sulfur-carbon composite with a unique hierarchical tower-like structure (S-HTC@pDA) for lithium sulfur cathode. The internal layer by layer structure is capable of uniformly dispersing of sulfur, providing a continuous electronic conductive path and shortening the Li+ transport distance, while the external pDA coating can inhibit the diffusion of polysulfide. Benefited from the smart design, the S-HTC@pDA electrode achieved an excellent cycling stability, realizing a high discharge capacity of 916 mAh g−1 at the first cycle and a capacity retention of 79.4% after 500 cycles at 1 C. Therefore, this work provides a new concept in structure design for high performance lithium sulfur cathodes.

We demonstrated an organic-inorganic composite as hole transport layer consisting of water-free PEDOT:PSS and tungsten oxide (WO3) nanoparticles, which enhanced the power conversion efficiency of normal-structure perovskite solar cells (PSCs). The PSC employing the WO3/PEDOT:PSS film as a hole transport layer exhibited better device stability and improved power conversion efficiency (PCE) with approximately 20% performance enhancement. The highest PCE obtained from WO3/PEDOT:PSS device was 15.1%, owing to simultaneous increments on short circuit current, open circuit voltage and fill factor. WO3 nanoparticles can fill out the pinholes of porous PEDOT:PSS layer, demonstrating a void-free and homogenous HTL surface. WO3/PEDOT:PSS composite demonstrated much higher charge conductivity and hole mobility than pristine PEDOT:PSS layer. The interface of perovskite absorber and WO3/PEDOT:PSS HTL also contained less defect density. The superior performance of WO3/PEDOT:PSS composite was attributed to the reduced current leakage, enhanced hole extraction characteristics, and less trap-assisted interfacial recombination via current density - voltage, electron microscopy (SEM, AFM and c-AFM), electrochemical impedance spectroscopy (EIS) and space-charge limited current–voltage (SCLC) measurements and analysis.

Herein, we report the surface treatment on Zr4+/Al3+ codoped α-Fe2O3 photoanode for high-performance photoelectrochemical water splitting. A high-temperature quenching exhibits the Zr4+/Al3+ codoping in α-Fe2O3 photoanode without damaging morphology. The presence of Zr4+/Al3+ codoping shows a cathodic shift in onset potential, but lack of increment in photocurrent reveals the major role of passivation and the minimum doping effect of aluminum. Additionally, CoOx cocatalyst exhibits increment in photocurrent with the greater cathodic shift in onset potential than the pristine α-Fe2O3 nanorods. The CoOx surface-reworked Zr4+/Al3+ codoped α-Fe2O3 photoanode displays the highest photocurrent of 1.5 mA/cm2 at 1.23 V vs. RHE (76% increment over the pristine α-Fe2O3) and 0.7 mA/cm2 at 1.0 V vs. RHE (102% increment over the pristine α-Fe2O3). The systematic characterization carried out using x-ray diffraction and scanning electron microscopy confirms that after Zr4+/Al3+ codoping, and surface treatment, the crystalline structure, and morphology of the photoanodes remains unchanged. X-ray photoelectron spectroscopy confirmed the existence of Zr4+/Al3+ codopants in the hematite nanostructure. The electrochemical properties of the photoanode suggest that Al3+ and Zr4+ codoping, as well as surface treatment with CoOx, cocatalyst lowers charge transfer resistance across the FTO/hematite interface, and hematite/electrolyte interface. This designs not only lowers onset potential but also offers the blueprint for the development of an efficient catalyst for solar water oxidation.

In this work, we report a new type anode material, MoO 2 combined carbon dots (CDs) with nanoparticle-stacking structure via a facile hydrothermal route. Herein, CDs is introduced as the reductant which in-situ reduces Mo VI to Mo IV . It is further confirmed that the particles of MoO 2 with evenly distributed beset of carbon dots form a nanoparticle-stacking structure. Thanks to this specific structure, the as-made MoO 2 -CDs manifest high performance in lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs). The capacities maintain 854 and 236 mAh g −1 at 0.50 A g −1 after 300 cycles for LIBs and 600 cycles for SIBs, respectively. Furthermore, we explored the structure-stability relationship by the electrochemical measurement and morphology, found the mechanisms of charge/discharge composed of dominant redox reaction and auxiliary intercalation reaction, and explained the characteristics of a high rate performance through kinetic issues and extrinsic pseudocapacitance contributions. This green synthetic method of anode material could make it possible to obtain high-performance alkali-ion batteries and other energy storage devices.

Lithium-sulfur (Li–S) battery system shows immense potential as energy storage devices with high energy density. However, the soluble property of polysulfides into the electrolyte during charge/discharge process leads to low sulfur utilization, severe polarization and short cyclic life, which has been a serious obstacle for practical application. How to anchor the polysulfides onto the cathode materials and moreover, enhance its further conversion to the final products, have been important challenges for the utilization of Li–S batteries. Herein, a novel well crystallized nanosized Fe7S8 possessing of a high specific surface area of 55.6 m2 g−1 fabricated by a simple microwave-assisted method combined with high temperature pyrolysis technique, is introduced into the S/C composite cathode for the first time. Strong interaction between polysulfides and the Fe7S8 can be realized to relieve the shuttle effect. The redox reaction of polysulfides can also be promoted to reduce electrode polarization. As a result of the enhanced utilization of sulfur, the optimized S@GFS-15 electrode may deliver a high initial discharge capacity of 1307.2 mA h g−1 at 0.1 C (1 C = 1675 mA h g−1) and low decay rates of 0.047% and 0.037% per cycle after 1000 cycles at 1 and 2 C respectively when the sulfur loading is ordinary 1.1 mg cm−2. Even the sulfur loading rises up to 2.6 mg cm−2, a large initial discharge specific capacity of 1134.5 mA h g−1 can be achieved at 0.1 C. After 600 cycles, the specific capacity of 457.3 mA h g−1 with a relatively small average decay rate of 0.062% per cycle can be obtained. Thus, incorporation of the nanosized Fe7S8 with graphene can help to achieve effective performance improvement route for Li–S batteries.

The effect of additives of transition metal cations (Zn2+, Cu2+, Co2+, Ni2+, and Mn 2+) on the passivation of lithium metal anode in Li–S batteries was investigated. The effects of transition cation additives on improving rate capability and Coulombic efficiency were observed in the following order: Zn2+ > Cu2+ > Co2+ > Ni2+ > Mn2+ > no salt. With Zn additives, less-accumulation of sulfur and smoother surfaces were observed using Scanning Electron Microscope (SEM) compared to that without additives. The result is consistent with Electrochemical Quartz Crystal Microbalance (EQCM) measurement, where less increase in mass changes of the anode for Zn additive as compared to Cu and no additive. The findings can be attributed to transition metal sulfides deposited on lithium surface cooperate with lithium sulfide and electrolyte decomposition product resulting in a smoother and more robust solid electrolyte interphase (SEI) films. The enhanced homogeneity of passivation layer greatly hinders the parasitic reactions between lithium metal and polysulfides as well as organic electrolyte, reducing the loss of active material and improving Coulombic efficiency. On the other hand, the uniform and mechanically strong SEI film introduces less undesired lithium plating and further accumulation on active sites, which significantly enhance the long-term stability due to improved surface morphology and chemistry. The results of this study provide a facile method of in-situ chemical formation of passivation layer protecting the lithium metal in batteries.

In this study, a new DMF-derived ionic liquid electrolyte [EDMF]BF4 was prepared, characterized and applied as a high-capacitance electrolyte for electric double-layer capacitors (EDLCs). [EDMF]BF4 was measured to have very high ionic conductivity and low viscosity (24.8 mS cm−1 and 21.6 mPa s at 25 °C), as well as a comparable electrochemical window (4.4 V, on a GC electrode) with [EMIm]BF4, which is one of the most widely studied ionic liquid electrolytes with high performance. Therefore, [EDMF]BF4 was used as a non-volatile electrolyte for activated carbon-based EDLCs. The [EDMF]BF4-based EDLCs are capable to operate stably over a voltage of 2.7 V, and the specific capacitance of activated carbon was determined to be 165 F g−1 (100th cycle at 1 mA cm−2 and 30 °C), which is much larger than in the case of [EMIm]BF4 (126 F g−1). Besides, [EDMF]BF4 showed lower ohmic resistance and double layer resistance than [EMIm]BF4 in EDLCs. The high performance of [EDMF]BF4 electrolyte should be related to the quasi-linear [EDMF] cation of moderate size, which is presumably more suitable for enhanced ion mobility and compact electric double layer.

This study adopts high-concentration ether electrolytes to improve high-rate capability, cycling stability, and Coulombic efficiency (CE) for lithium ion batteries with lithium anode. A series of ether-based electrolytes including lithium bis(fluorosulfonyl)imide (LiFSI)-glyme/ethylene carbonate (EC), LiFSI-glyme/EC, LiFSI-diglyme/EC, LiFSI-triglyme/EC, LiFSI-tetraglyme (G4)/EC, and LiFSI-1,3-dioxolane (DOL)/EC, along with commonly used LiPF6-DEC/EC were prepared to delineate the influences of concentration, chain length, molecular structure (linear or ring ether), and EC additive on the electrochemical performance of Li anodes. An optimum composition for ether-based electrolyte was determined resulting in significant improvement in anti-flammability as well as CE at both low and high rates. At ultra-high current density operation (e.g. 6 mA cm−2), the CE was 95.5 and 97.1% with 3 M LiFSI-G4/EC and 3 M LiFSI-DOL/EC, respectively. Using 1 M LiPF6 carbonate-based electrolyte tend to grow a needle-like dendritic structure when depositing lithium metal on Cu foils, whereas high-concentration ether electrolyte promotes a knot-like and rounded Li metal microstructure. High concentration EC-based electrolytes, are capable of facilitating Li+ almost in tandem with solvent molecules, thereby reducing the number of free molecules, reducing the chance of side reaction with Li metal, and subsequently inhibiting the formation of dendritic Li structures.

Advanced operando spectroscopic techniques monitor real-time changes in crystal structure, oxidation state, coordination environments, and chemical evolution of Na-ion host anodes during charge-discharge cycles . Operando spectroscopy techniques include Raman spectroscopy, nuclear magnetic resonance, powder X-ray diffraction, X-ray adsorption fine structure, X-ray absorption near edge and extended X-ray absorption fine structure, which provide outstanding scientific understanding of anodes for the next generation of Na-ion batteries. This review systematically summarizes intercalation, alloying, and conversion anodes investigated through operando spectroscopy techniques. These have generated a profound and fundamental understanding of diverse phenomena occurring on the active material surface and/or bulk during the electrochemical reaction conditions, such as phase transitions, side reactions, lattice parameter changes, and molecular scale structure-reactivity relationships.

Cube-like anatase TiO2 mesocrystals have been fabricated successfully by using amorphous titanate as a precursor. The size and shape of the synthesized mesocrystals are uniform with an average size of 100 nm. Interestingly, the low index facets of (100), (010) and (001) are exposed completely, forming the special cube-like shape. When used as an anode for lithium-ion batteries, anatase TiO2 mesocrystals exhibit an excellent lithium storage ability. A capacity of 166 mA h g−1 can be remained after 800 cycles at 5C, demonstrating a good long-term cycling performance. Furthermore, an average reversible capacity of 148 mA h g−1 can be also maintained even at a rate as high as 20C. Such an excellent electrochemical performance can be attributed to the special cube-like shape of TiO2 mesocrystals with exposed facets, which facilitate lithium-ion diffusion.

Zinc cobalt sulfide (ZCS) is a promising and high performance electrode material for pseudocapacitors due to its good electrical conductivity, abundant active sites and rich valence states. In this work, zinc cobalt oxide (ZCO) nanoparticles are firstly synthesized via a hydrothermal method assisted by hexadecyltrimethyl ammonium bromide (CTAB), and then transformed into zinc cobalt sulfide nanoparticles (ZCS NPs) using a facile sulfuration process. The average diameter of ZCS NPs is estimated to be about 15 nm, which is beneficial for Faradaic redox reactions in energy storage process due to their numerous active surfaces. The ZCS NPs are then coated onto a nickel foam to form the working electrode of supercapacitors. Because the ZCS electrode has lower series and charge transfer resistance, and also higher ion diffusion rate than that of the ZCO electrode, it achieves a large specific capacitance of 1269.1 F g−1 at 0.5 A g−1 in 2 M KOH electrolyte, which is four times more than that of the ZCO electrode (e.g., 295.8 F g−1 at 0.5 A g−1). In addition, an asymmetric supercapacitor using the ZCS NPs as the positive electrode and activated carbon as the negative electrode is assembled, which delivers a high energy density of 45.4 Wh kg−1 at a power density of 805.0 W kg−1, with an excellent cycling stability (91.6% retention of the initial capacitance over 5000 cycles).

Considering severe threat of bisphenol A (BPA) to environment and human health, it is urgent to develop a convenient and specific method for accurately detecting BPA. An efficient photoelectrochemical (PEC) aptasensor for determining BPA in water is constructed using Bi microspheres/carbon nitride (Bi/CN) heterojunction as a PEC material. The promoting effect of Bi on the enhanced PEC performance of Bi/CN heterojunction is initiated by two unique effects: the construction of heterojunction (heterojunction effect) and surface plasmon resonance (SPR) effect. For heterojunction effect, a metal-semiconductor heterojunction of Bi/CN is constructed, which increases the light absorption of CN, generates more electron-hole pairs and accelerates the separation of carriers. Simultaneously, as a plasmonic metal, Bi microspheres accelerate charge transfer generated from the heterojunction. This function of Bi is of high benefit to suppress the electron-hole recombination, leading to an enhanced PEC performance. Benefiting from enhanced PEC performance of the heterojunction, a sensitive PEC aptasensor for detecting BPA is realized. This work demonstrates that the Bi/CN heterojunction amplified photoelectric conversion strategy can be used as an efficient method for Bi-based materials to significantly enhance the PEC performance and also provides more opportunities for application of Bi-based materials in PEC field.

A potential-responsive 2-2′-dithiodibenzoic acid (DTSA)/Polyaniline (PANI) hybrid film with high ion-exchange capability and selectivity to cadmium ions was successfully fabricated on electrode by a one-step cyclic voltammetry (CV) method. S–S bonds in the DTSA serve as a gate that can be controllably opened and closed to let cadmium ions get in and out of the hybrid film when changing its redox state, and the PANI mainly enhanced the conductivity of the hybrid film. The working mechanism of the film is proposed and identified via the electrochemical quartz crystal microbalance (EQCM) technique, X-ray photoelectron spectroscopy (XPS), Raman and density functional theory (DFT) computations. As a result, the obtained hybrid film exhibited high selectivity towards cadmium ions even in the presences of other cations. More interestingly, over 240% of its initial capacity was retained after 25 consecutive cycles and maintained in the following cycles. Furthermore, the regeneration rate of the hybrid film retains 99% of its initial value even after 30 cycles. It is expected that such a potential-responsive film can be applied for the removal and recovery of cadmium ions from wastewater in various industrial processes.

A binder free battery type supercapacitor electrode composed of 3D hierarchical dandelion-fiber flake-like structure has been synthesized by cost-effective, layer by layer (LbL) method for 10, 20, 30, 40 and 50 LbL cycles on flexible stainless-steel substrate. Among all the synthesized working electrodes, 40 LbL cycles shows the prominent electrochemical performance with a wide operating potential window (−1.0 to +1.0 V) in 1.0 M aq. Na2SO4 electrolyte. The maximum specific capacity of 958 C g−1 (maximum specific capacitance 479 F g−1) for 1 mA current rate has been achieved by using the three-electrode system. The novel composite material Al(OH)3/MnO2 shows the battery type supercapacitor electrode that comprises the high electronic conductivity with a better electrocapacitive performance that improves the energy storage capability. For having the deeper insight of charge storage mechanism, we evaluate the contribution of charges coming from the individual surface capacitive and diffusion-controlled process. The galvanostatic charge discharge illustrates good cyclic reversibility of composite film whereas electrochemical impedance spectroscopy (EIS) demonstrate the capacitive behavior of nanocomposite thin film with a low value of Rct ∼ 0.01 Ω cm−1. Therefore, it could be anticipated that Al(OH)3/MnO2 nanocomposite thin film is a promising electrode material for flexible and portable electronic devices, electric vehicles, etc.

In this work, a novel dual-analyte electrochemical sensor was developed based on the combination of boronate affinity and indicator displacement assay (IDA) strategy. Reduced graphene oxidation (RGO) and poly(3-aminophenylboronic acid) (pAPBA) were modified on glassy carbon electrode (GCE), which further bound dopamine (DA) via a reversible covalent interaction between the APBA and DA. Due to the higher affinity of pAPBA to the analytes, the bound DA can be displaced by fructose (Fru) or Alizarin Red S (ARS). As an indicator, the decrease of DA current caused by the displacement was used to monitor the concentration of the analyte. For non electro-active molecule, the decrease of DA current was directly proportional to the logarithm of Fru concentration in a range from 7.0 × 10 −8 to 1.0 × 10 −4 mol/L. For electro-active molecule, the current of DA decreased along with the increase of ARS current owing to the displacement, which were combined as a dual-signl for ARS sensitive detection with a linear range of 9.0 × 10 −8 - 1.0 × 10 −5 mol/L. The results of determining analytes with their interferences demonstrated the good specific affinity of the sensor toward the analytes. The dual-analyte electrochemical sensor based on IDA strategy probably provides a potential guidance for multi-analyte facile, sensitive, and specific detection.

The electrooxidation of ethanol with Pt/C, PtRu/C and Pt3Sn in alkaline electrolyte has been studied using electrochemical coupled infrared spectroscopy. In order to identify the evolution of the species formed during the electrooxidation of ethanol infrared spectra have been collected in KOH/H2O and KOD/D2O electrolytes. Whereas the electrochemical studies show different catalytic performance for the EOR (Ethanol Oxidation Reaction) over the three catalysts in terms of onset potential and actual current density, especially at low potentials, the IR spectra show that carbonates and acetates are the main species formed during the EOR with all catalysts. The infrared spectra reveal that the scission of the C–C bond of ethanol takes place at the surface of Pt/C, PtRu/C and Pt3Sn catalysts at potentials as low as 20 mV vs RHE yielding carbonates. At higher potentials, C2 species resulting from the partial oxidation of ethanol to acetates are the main species detected with all catalysts. Upon the progress of the ethanol oxidation, the electrolyte becomes acidified and acetaldehyde and acetic acid (C2 species typically formed during the EOR at acid electrolyte) are observed.