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Proximal configuration of dissimilar metal atoms in amorphous high-entropy-alloys (HEAs) always result in interatomic d-band ligand effect, dense defect distribution, coordinatively unsaturated sites, high potential energy, and loose atom bonding. Herein, nanostructured amorphous Fe29Co27Ni23Si9B12 HEA ribbon is fabricated via a melt spinning method combined with electrochemical corrosion etching process, which is applied as the potential oxygen evolution reaction electrocatalyst. It is found that there are micro/nano pits on the surface of etched amorphous Fe29Co27Ni23Si9B12 ribbons. Various elements of HEAs bond with each other to form a highly disordered configuration, which could result in an optimized bonding energy and enhanced intrinsic catalytic activity. The electrocatalysis activity measurements indicate that the amorphous HEAs endows a much higher activity than the crystalline one, which is further improved by the electrochemical etching treatment. Especially, the HEA ribbon etched for 3 h requires a low overpotential of 230 mV to afford 10 mA cm-2 current density. In addition, density functional theory calculations demonstrate that the amorphous structure can weaken the interaction between the surface of Fe29Co27Ni23Si9B12 alloy and the intermediates, leading to an optimized adsorption Gibbs free energy.

Conversion of CO2 into valuable chemicals via electrochemical CO2 reduction reaction (CO2RR) is a promising technology to alleviate the energy crisis and the greenhouse effect. Herein, low-cost woo...

In this work, the unipolar pulse electrodeposition (UPED) method is used to electrodeposit the conductive polyaniline (PANI) on the carbonized polyhedron zeolitic imidazole particles (C-ZIF-8). The composite film of C-ZIF-8/PANI coated on the flexible substrate stainless steel wire mesh (SSWM) offers large contact area between the electrode material and the electrolyte, which provides enough active sites for charge storage. The obtained flexible electrode exhibits efficient-specific capacity of 363 F g−1 with 300° stretching angle and excellent long-term cycling stability after 10,000 cycles at 5 mA g−1 in 1 M H2SO4 electrolyte. It is found that the flexible electrode shows obvious improvement in the electrochemical properties when it was bent or stretched. Asymmetrical all-solid-state supercapacitor device is fabricated by using polyvinyl alcohol (PVA) solid gel as electrolyte and separator, which shows general gravimetric capacitance of 147, 156, and 156 F g−1 with energy densities of 8.66, 9.16, and 9.16 W kg−1 at stretching angle of 0°, 120°, and 300°, respectively, and stable power density of 162.5 W kg−1 in the different conditions. It indicates that such a composite C-ZIF-8/PANI/SSWM is a favorable material for portable and flexible energy storage.

Mercury (Hg), and its organic forms, are some of the most hazardous elements, with strong toxicity, persistence, and biological accumulation in marine organisms. Hg accumulation in continuous trophic levels (TL) in marine food chains remains unclear. In this study, individual invertebrate and fish samples collected from the Yellow River Estuary adjacent sea were grouped into continuous TL ranges, and the bioaccumulations of total Hg (THg) and methylmercury (MeHg) were analyzed. The trophic magnification factor in invertebrates and fish was 1.40 and 1.72 for THg, and 2.56 and 2.17 for MeHg, indicating that both THg and MeHg were significantly biomagnified with increasing TL in both invertebrates and fish through trophic transfer. To evaluate the health risk of seafood consumption, the target hazard quotient (THQ) was calculated. Increasing THQ values indicated that the health risks of invertebrate and fish consumption in humans, especially children, were both elevated with increasing TL. THQ values 1 indicated that consumption of invertebrates at a TL above 4.0 and fish above 4.5 may pose a relatively higher risk for children. Therefore, the consumption of both individual invertebrates and fish at high trophic positions may present greater health risk, especially in young children.

In this study, octahedral molecular sieve (OMS-2) is successfully delaminated by using trace holmium (Ho) via a facile redox co-precipitation route, which exhibits high performance for the total toluene oxidation at low temperature. High resolution transmission electron microscope (HRTEM), X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance (EPR) analyses verify that abundant multi-phase interfaces and lattice dislocations are formed on the obtained delaminated OMS-2 by the Ho (Ho-OMS-2), which can induce more active oxygen species. In particular, the delaminated OMS-2 with a trace Ho amount has a high Oads/Olatt ratio with a balanced ratio of Mn3+ and Mn4+, demonstrating much higher activity (T100% of 228 °C even under 5 vol% H2O vapor over 0.5% Ho-OMS-2) than the parent OMS-2 (T100% of 261 °C) for the total toluene oxidation. Furthermore, the positive effect of the introduction of H2O on catalytic activity, especially the enhancement of the conversion of intermediates into CO2 and H2O, is verified by the in situ diffuse reflection infrared Fourier transform spectroscopy (DRIFTS). Based on these results, the reaction mechanism for toluene oxidation over the OMS-2 based catalyst is proposed. It is expected to provide an effective preparation method to obtain high-performance catalysts for the VOCs oxidation at low temperatures.

A novel hexagonal prism Copper (II) metal organic framework (Cu-BTC) was first synthesized by using a facile unipolar pulse electropolymerization method. It has been found that the morphology of Cu-BTC crystals can be changed from octahedron to hexagonal prism with the increase of pulse cycles. The XRD pattern confirms that the crystal structure of Cu-BTC was slightly affected by the change of the crystal morphology. Furthermore, the growth mechanism of hexagonal prism Cu-BTC crystals was proposed. This method provides valuable guidelines for the design of other MOFs and opens up new opportunities for exploring their application.

Water defluoridation still remains challenge since most of currently applied fluoride adsorbents always have low adsorption capacity with difficulty in regeneration. Herein, NiMn-layered double hydroxide (NiMn-LDH) nanosheets coated conductive multiwalled carbon nanotubes (MWCNTs) were successfully fabricated on the electrode via a unipolar pulse electrodeposition (UPED) method for efficient water defluoridation. It is found that the NiMn-LDH nanosheets with large surface areas can be grafted uniformly on the skeleton of conductive MWCNTs to facilitate the electron transport. Compared to ion exchange (IX) process, faster and more efficient reversible uptake/release of fluoride ions (F−) was realized by modulating the positive and negative charges on the electrical double layer (EDL) of the composite, coupling with ligand exchange at the active sites of NiMn-LDH during the electrochemical redox process. Especially, in a broad pH range (4–10), the electroactive MWCNTs@NiMn-LDH can remove F− effectively. Moreover, the F− adsorption onto MWCNTs@NiMn-LDH followed the pseudo-second-order model, with the maximum F− adsorption quantity of 135.1 mg/g from the Langmuir model. After 5 uptake/release cycles, ion exchange quantity still retained 92.4% of its initial value. Furthermore, the EDL ion transport coupled with ligand exchange mechanism in MWCNTs@NiMn-LDH was verified by XPS analysis. The continuous F− separation runs implied that the flux of F− by MWCNTs@NiMn-LDH was twice over that of by MWCNTs only while the time of the concentration reached even below WHO standard was quarter of that of by MWCNTs only. It is concluded that the MWCNTs@NiMn-LDH is a promising electroactive material for defluoridation, especially combining it in electrochemically switched ion permselective (ESIP) system can realize a continuous F− separation.

Bismuth oxychloride (BiOCl)-coated electroactive film was fabricated for the separation of cesium ions based on a potential-triggered method. The effects of applied potential, conductive carbon black (Super P Li), and different exposed facets on the adsorption of Cs+ ions were investigated. Experiments revealed that the adsorption efficiency gradually improved with increasing the applied potential to −0.7 V. The introduction of Super P Li improved the adsorption rate and increased the separation efficiency. The adsorption behavior followed pseudo-second-order kinetics. Additionally, the electroactive film showed adsorption selectivity for Cs+ in preference to Li+, Na+, and Rb+; seven consecutive adsorption–desorption experiments indicated that the electroactive film is sensitive to potential. The BiOCl nanosheets with exposed (001) facets exhibited a higher adsorption ratio for Cs+ removal than the counterpart with exposed (101) facets. It was also found that the separation performance of Cs+ ions was bes...

Multiple active sites containing ionic liquid (IL) tetrabutylphosphonium 2-hydroxypyridine ([P4444][2-Op]) is prepared and loaded into mesoporous silica vesicle (MSV) with three kinds of pore structure for fabricating ionogels to capture CO2 from simulated flue gas (CO2/N2). The ionogel MSV100-10 achieves CO2 adsorption capacity of 1.69 mmol·(g-ionogel)–1 (that is 11.77 mmol·(g-IL)–1) in less than 10.0 min at 50 °C and CO2 partial pressure of 0.2. The high adsorption capacity and rate can be ascribed to its large pore size and pore volume, which offer not only enough nanospace for highly dispersed IL but also necessary pathway for fast diffusion of guest molecule CO2. Small mesopores of the supports benefit to form monomolecular layers for the lowly loaded IL due to their strong nano-confinement effect but are easily blocked by highly loaded IL. The support with large vesicle-like pores allow the formation of IL pairs for the lowly loaded IL due to their weak nano-confinement effect and keep necessary pathway for CO2 diffusion in the highly loaded ionogel. The ionogel MSV100-10 performs capacity retention of 95% after 10 sorption cycles. The ionogel MSV100-10 featuring with low loading and cost, rapid adsorption, high capacity and excellent cyclic stability make it a competitive candidate in CO2 capture from flue gas.

PbO2 electrode is one of crucial materials in electrochemical field, however, the fabrications of nanostructured PbO2 materials are highly confined to the template method. In this work, the nanostructured PbO2 materials were controllably synthesized by template-free electrodeposition method. It is found that the microstructure of PbO2 material was highly depended on the electrochemical deposition models, i.e., cyclic voltammetry (CV) method, potentiostatic method (PM), pulse potentiostatic method (PPM) and pulse galvanostatic method (PGM). Especially, PbO2 nanorod built by nanoparticles with chrysanthemum-like array synthesized in the absence of template by pulse potential deposition method showed high specific capacitance and good stability for supercapacitor application.

To achieve superior specific capacitance with sound cyclic stability, porous manganese dioxide (MnO2) film built from arborization-like nanoclusters is deposited for the first time on multi-walled carbon nanotube (MWCNT) pre-covered onto Pt sheet by using a unipolar pulse electro-deposition method. The obtained composite electrode MnO2/MWCNT displays unique nanostructure and good stability. It displays specific mass capacitance as high as 553.0 F/g in 0.50 M Na2SO4 solution. The attractive capacitance performance may contribute from the synergetic effects of chemical adsorption-desorption on the spherical surface and internal intercalation/deintercalation between electrolyte ions and active material MnO2. After 2000 charge/discharge cycles at the current density of 5.0 A/g, it can retain more than 97% of the initial specific capacitance. The superior cyclic stability may depend on the well crystallized MnO2 containing more bond Mn-O-Mn but less bond Mn-O-H. In case of its counterpart MnO2/MWCNT-PM prepared using potentiostatic method, its low capacitance performance can be ascribed to the simply chemical adsorption-desorption on its flat surface between electrolyte ions and active MnO2. It can only retain about 62% of the first cycle capacitance after the charge/discharge cycles. The poor cyclic stability mainly depends on the lowly crystallized MnO2 containing more bond Mn-O-H but less bond Mn-O-Mn.

Recently, the composite of spinel-type manganese oxide (λ-MnO2)/graphene has drawn wide attention because of its good electrochemical adsorption selectivity for low concentrations of Li+ ions from lake brine or seawater to cope with the fast-rising demand of lithium resources. In this composite, the synergistic effect between the good selectivity of λ-MnO2 for Li+ ions and the excellent conductivity of graphene play an important role for the electrochemical adsorption of Li+ ions. In order to reveal the synergistic mechanism in the electronic conductivity, the ionic conductivity and the ion selectivity of the λ-MnO2/graphene composite, density functional theory (DFT) calculations combined with electrochemical adsorption experiments were carried out. The calculation results show that the enhanced electronic conductivity of the composite is due to the decrease of the band gap (Eg) in the λ-MnO2/graphene composite compared with pure λ-MnO2. Meanwhile, the graphene composited with λ-MnO2 decreased the diffusion energy barrier of Li+ ions in λ-MnO2. In addition, the competitive adsorption of Li+, Na+ and Mg2+ ions were investigated by the nudged elastic band (NEB) method and charge distribution analysis. The results show that Li+ ions in λ-MnO2 exist in their pure ion state and have the lowest diffusion energy barrier compared with Na+ and Mg2+. The results of the DFT calculations were validated by cyclic voltammetry, electrochemical impedance spectroscopy and electrochemical adsorption experiments.

Conversion of CO

Developing low-cost electrocatalysts with outstanding electrochemical performance for water splitting over a wide pH range is urgently desired to meet the practical needs in different areas. Herein, a highly efficient hierarchical flower-like CoS

In this study, CoNi-layered double hydroxide (CoNi-LDH) nanosheets coated conducting polypyrrole (PPy) nanowire was controllably fabricated on Pt plate or carbon cloth by using unipolar pulse electrodeposition (UPED) method and served as a novel electrochemically switched ion exchange (ESIX) hybrid film with proton-ligand effect for the removal of perchlorate anions (ClO4−). It is expected that the space among CoNi-LDH nanosheets of the shell could act as the reservoir for the anions while the PPy core serve as the potential-induced element for proton-ligand. The effects of pulse potential during film deposition and initial pH of the wastewater on the ClO4− removal performance of this core-shell hybrid film were investigated. It is found that ClO4− adsorption onto PPy@CoNi-LDH followed pseudo-second-order model, and the film fabricated with −1.5 V pulse potential showed an excellent performance for the rapid removal of ClO4− with a high selectivity, and the ClO4− adsorption quantity reached as high as 302 mg g−1. In a wide pH range (3–10), the hybrid film removed ClO4− efficiently. The proton-ligand effect in PPy@CoNi-LDH was proved by using XPS analysis and density functional theory. Such a PPy@CoNi-LDH hybrid core-shell film should be a potential electroactive material for the separation of ClO4− and other anions from wastewater.

Oxygen-enriched porous electroactive carbon (OPEC) is prepared by simply carbonizing salted seaweed and only washing with water. The recrystallized NaCl cube is chemically stable and mainly acts as a pore filler in the pristine seaweed. It helps to maintain the innate pore system and simultaneously templates the formation of square pores. Its shielding effect not only enhances the onset decomposition temperature but also helps to achieve high yield. It can also be completely removed by washing with the green solvent water. The obtained OPEC-800 material not only shows a specific surface area of 329.3 m2 g−1 but also a microporous structure (0.8–2.0 nm) matching with the electrolyte 1.0 M H2SO4. It exhibits a specific capacitance of 324.3 F g−1 (specific surface-area capacitance is 98.5 μF cm−2) at a current density of 0.50 A g−1 in a three-electrode system. Its high oxygen content of 19.1% can lead to a wide operating voltage window of 0.0–1.40 V and an attractive energy density of 15.9 W h kg−1 at a power density of 175.0 W kg−1 in a two-electrode system. Furthermore, it also displays an excellent cyclic stability (98%, 10 000 cycles) and good rate performance. The whole process is a green, oxidant-free, acid-free, and low-cost method for converting green biomass into self-functionalized carbon with naturally connected pores aiming to fabricate green energy devices. All the attractive features make the environmentally friendly route a competitive candidate for preparing other porous electroactive materials.

A novel electric-field-accelerated ion-sieve membrane (EISM) system with potential-oscillation was set up for the selective separation of the alkali metal ions. The ion-sieve membrane was fabricated by coating a polypyrrole/polystyrenesulfonate composite on the stainless steel wire mesh (PPy/PSS/SSWM). In the EISM system, an external electric filed was applied by introducing a constant cell voltage on the two sides of the ion-sieve membrane to accelerate the directed transport of target ions through the membrane. Meanwhile, an extra pulse potential was applied on the PPy/PSS/SSWM membrane to adjust the ion binding ability of the PPy/PSS composite toward cations. As such, an enhanced “ion sieving effect” of the EISM system was achieved through the synergistic function of the constant cell voltage and potential oscillation, which resulted in the rapid transport of target cation across the membrane in a “leap-frogging” way. It is found that when an extra pulse potential of ±1.0 V (pulse width of 60 s) was applied on the EISM, the permeation flux of K+ ions was increased by 7.42-fold with a constant cell voltage of 5 V. The permselectivities of the PPy/PSS/SSWM membrane for K+/Li+ and K+/Cs+ reached 3.29 and 3.45 respectively based on the optimized amplitude (±1.0 V) and frequency (pulse width of 60 s) of pulse potential.

A carbonized HKUST-1@CoAl layered double hydroxide (HKUST-1(C)@CoAl LDH) film with a three-dimensional (3D) porous structurewas successfully prepared on the copper mesh by using a two-step electrochemical deposition method, and applied in a novel unipolar pulse potential oscillation (UPPO) system for selective separation of dilute dodecyl sulfonate ions (DS−). In the HKUST-1(C)@CoAl LDH film, the CoAl LDH was served as a separating layer to improve the selectivity for DS− ions with the HKUST-1(C) as a storage layer to increase the adsorption amount of DS− ions. As a result, the 3D HKUST-1(C)@CoAl LDH film coated electrode showed excellent selectivity toward DS− ions with a high adsorption capacity of 733.84 mg g−1 and favorable electrochemical stability. More importantly, it is found that such a novel UPPO system can effectively reduce the influence of co-existing anions on the adsorption of DS− ions and accelerate the transport of DS− ions in the film by the periodic potential oscillation, which is expected to be used for the selective separation of DS− ions from practical wastewater.

Well-aligned CuO nanowire@Co 3 O 4 nanosheet core-shell array was successfully fabricated on carbon fibers by multi-step electrodeposition combined with thermal treatment and applied as the binder- and conductive-agent-free anode for oxygen evolution reaction (OER) in water electrolysis process. Such an anode revealed an overpotential of 258 ± 3.2 mV at a current density of 10 mA cm −2 in 1.0 mol L −1 KOH solution, which is much lower than that of pure CuO nanowires or Co 3 O 4 nanosheets based electrode. This should be attributed to the smart hybridization of CuO nanowires and Co 3 O 4 nanosheets into hierarchical core/shell array configuration which could largely increase the amount of contact areas between electrolyte and active sites. Moreover, it is found that the Cu 2+ in CuO/Co 3 O 4 composite was oxidized to Cu 3+ components during the OER process, which should serve as the new catalytic active sites for OER. It is expected to provide a novel route to prepare such a core-shell electrocatalyst with high performance for water splitting.

A unipolar pulse electrodeposition method was employed to controllably synthesize nanosheet type NiCo LDH. The effect of concentration rate of Ni(NO3)2/Co(NO3)2 preparation solution on crystalline structure, morphology and supercapacitive performance was investigated systematically. Experimental found that the morphology and composition of NiCo LDH was highly depend on the Ni2+/Co2+ molar ratios of preparation solution; and the obtained Ni0.76Co0.24 LDH materials showed small nanosheet size and uniform distribution on carbon fiber electrode. Ni0.76Co0.24 LDH electrode was evaluated for supercapacitor application, which revealed a high specific capacitances of 2189.8 and 1908.8 F g−1 at the current density of 1 and 30 A g−1 respectively and a good cycle stability, retaining 70.3 % of the initial capacitance after 20000 charge and discharge cycles at 50 A g−1. Moreover, the Ni0.76Co0.24 LDH electrode exhibits a high energy density of 76 Wh Kg−1 at a power density of 250 W Kg−1 and a high power density of 7500 W Kg−1 at energy density of 66 Wh Kg−1. The as-prepared Ni0.76Co0.24 LDH as positive electrode for asymmetric supercapacitor exhibits excellent energy density of 4.1 Wh Kg-1 at a power density of 4000 W Kg-1

To develop a kind of flexible electrode for supercapacitors working in neutral electrolyte, nickel hexacyanoferrate nanocubes (NiHCF-NCs) are uniformly deposited on flexible carbon fibers (CFs) by using a facile unipolar pulse electrodeposition (UPED) technique. It is found that NiHCF film prepared by UPED is composed of NCs with more uniform size than those prepared by the common cyclic voltammetry (CV) and potentiostatic (PM) methods. Pulse potential of UPED has significantly influence on the morphology and crystal structure. Uniform NiHCF-NCs with approximately 200 nm side length are successfully formed on flexible CFs at 0.3 V. Moreover, the ratio of two structures of NiHCF, i.e., “insoluble” and “soluble” structures, can be well controlled by the applied pulse potential. Electrochemical performances are characterized by CV, galvanostatic charge/discharge and electrochemical impedance spectroscopy tests. NiHCF-NCs film on flexible carbon fibers prepared at 0.3 V applied pulse potential exhibits remarkable electrochemical performance with a capacitance as high as 476 F g−1 at 0.2 A g−1 in the neutral electrolyte, and the capacitance retains 92.5% of its initial value after 8000 charge/discharge cycles. It indicates that such a simple, cost-effective and readily scalable NiHCF-NCs film fabrication method has commercial potential for preparation of flexible electrode for high performance supercapacitors working in neutral electrolyte.

BiOCl was found to have excellent electrochemical adsorption properties for cesium ions (Cs+) in electrochemically switched ion exchange (ESIX). In this work, BiOCl nanosheets were synthesized by a hydrothermal method and used for electrochemical adsorption of Cs+. The experimental results showed that BiOCl exhibited higher electrochemical adsorption selectivity for Cs+ than Li+ and Na+. Quantum chemical calculations based on density functional theory (DFT) were first performed to compare the adsorption and migration mechanisms of three ions Li+, Na+, and Cs+ in BiOCl crystals. The calculation results revealed that the excellent electrochemical adsorption performance of BiOCl for Cs+ is due to the interaction of embedded Cs with Cl and Bi in BiOCl crystals. This makes it have a higher adsorption energy and a lower ion migration energy barrier due to the balance of interaction forces. In this work experimental and theoretical calculations were used to systematically analyze the adsorption and migration of three ions in BiOCl, which has important guiding significance for the design of highly-efficient electroactive materials for electrochemical adsorption of Cs+.

Recently, the composite of spinel-type manganese oxide (λ-MnO

The high-entropy materials have attracted rising attention for electrolysis application, which may have unusual performances due to the proximal configuration of dissimilar atoms. Meanwhile, design of nanostructure and fine-tuning of crystal structure could further improve their properties. In this work, amorphous FeCoNiPB high-entropy alloy (HEA) ribbons are prepared first, whose superficial species are conversed to FeCoNiPB/(FeCoNi)3O4-x composite nanoparticles with a diameter of ~15 nm by the air after acid etching treatment. It is found that the obtained composite nanoparticles deposited on the surface of FeCoNiPB HEA ribbon with 3D porous array. Besides, the (FeCoNi)3O4-x crystal that derived from amorphous HEA has rich defect structure, including lattice distortions, vacancy defects and discontinuous crystalline fringes. Hence, due to the advantages of heterogeneous nanostructure and defect activation, the FeCoNiPB/(FeCoNi)3O4-x nanoparticle modified HEA ribbon has a high catalytic activity for oxygen evolution reaction, which need low overpotentials of 229 mV and 406 mV to export 10 and 100 mA cm−2 current density with a good stability.

Highly selective ion separation is crucial to engineering applications. In this work, inspired by the working mechanism of biological protein ion channels, inclusion of ion-imprinted conductive polymers inside metal-organic frameworks (MOFs) with size selective effect was considered for the effective separation of ions. In-situ polymerization of polypyrrole (PPy) with anion exchange behavior in the UiO-66 cages was performed to obtain a conductive chlorine ion-imprinted polymer film electrode (Cl-IIP@UiO-66) for the electrochemically selective separation of chloride ions (Cl−) from wastewater. Herein, the chlorine ion-imprinted conductive PPy chains not only tuned the pore size of UiO-66, but also provided ion and electron transport channels at the molecular scale. As a result, the Cl− ion exchange capacity of the Cl-IIP@UiO-66 coated electrode reached to 52.16 mg g−1 with an adsorption equilibrium time less than 4 h under the extra electric field. Meanwhile, the Cl-IIP@UiO-66 film exhibited high separation factors of 9.02, 10.29, 13.41 and 18.50 for Cl−/Br−, Cl−/F−, Cl−/SO42− and Cl−/PO43−, respectively, which was mainly attributed to the anion-imprinting effect and the nanostructure for the selective recognition for Cl− ions. Remarkably, based on the controlled swelling property of MOFs, the Cl-IIP@UiO-66 maintained superior electrochemical reversibility and durability over 98% even after 1000 uptake/release cycles. Hence, it is believed that such a novel electroactive Cl− ion-imprinted film electrode could be a promising candidate for wastewater treatment. Also, it opened a new pathway to develop novel MOF-based electroactive ion exchange materials for various ion separations.

A novel α-zirconium phosphate (α-ZrP) nanosheet-implanted fibrous polyaniline (PANI) hybrid film with potential-responsive ion exchange function is fabricated by a facile pulse electrochemical synthesis technique. The suppression effect of electrical double layer at the conducting substrate/colloidal solution interface for the formation of PANI/α-ZrP hybrid film is effectively improved through a layer of pre-deposited PANI oligomers, whose thickness plays an important role in the self-assembly of the hybrid film. During the pulse electrochemical synthesis process, the oligomers-grafted fibrous PANI is electropolymerized in the period of high potential; and the translucent exfoliated α-ZrP nanosheets are uniformly implanted into the fibrous PANI by electrostatic self-assembly in the following period of low potential. The amount ratio of α-ZrP nanosheet and fibrous PANI can be regulated by adjusting the pulse width based on their growth rate. The results show that the optimized pulse width for the fabrication of PANI/α-ZrP hybrid film with three-dimensional porous structure is 0.8 s. Under this condition, the generated PANI/α-ZrP hybrid film shows fast uptake/release ability and high capacity for the separation of Pb2+ ions from aqueous solution based on its unique potential-induced ion exchange process. The adsorption equilibrium time is less than 30 s, and the ion exchange capacity of porous PANI/α-ZrP hybrid film reaches 123.5 mg g−1, which is almost 9 times higher than that of the compact PANI/α-ZrP hybrid film. Furthermore, the ion exchange capacity retains 85.2% of its initial value after 1000 cycles.

NiFe-layered double hydride (NiFe-LDH) coated Cu(OH) 2 array was well fabricated on carbon paper as anode by using a facile unipolar pulse electrodeposition (UPED) method for electrochemical water splitting. Effects of the initial molar ratio of Ni/Fe in the deposition solution, applied pulse potential, applied quantity of electricity on the performance of anode were investigated. The optimum Cu(OH) 2 nanorod @ NiFe-LDH nanosheet core/shell array structure was successfully obtained with an initial Ni/Fe molar ratio of 6:4 in the deposition solution, an applied pulse potential of −1.1 V and an applied quantity of electricity of 2.5 C by using the UPED method, which also showed a small overpotential of 283 mV to yield a current density of 10 mA cm −2 and a good stability during water electrolysis. It is expected to provide a new way to prepare anode with low cost and high performance for water electrolysis.

To understand steam reforming of methanol (SRM) reaction pathways over the surfaces of various metal-modified molybdenum carbides, the reaction intermediate species generated during the SRM reaction are investigated by using a temperature programmed surface reaction (TPSR) approach, in which a mass spectroscopy is applied to detect the produced species on-line. It is found that the reaction temperature affects the formation of different intermediate species over different catalysts. At the temperature lower than 180 °C, SRM reaction proceeds over Cu modified molybdenum carbide surface through formic acid (HCOOH) intermediate pathway, but at the temperature over 180 °C, the reactions over pure β-Mo2C, Ni, Cu and Pt modified molybdenum carbide surfaces proceed through methyl-formate (HCOOCH3) intermediate pathway. It is expected that these findings can help us to understand the mechanism on SRM reaction over molybdenum carbide based catalysts.

Yarn supercapacitors have received much attention because of their noticeable role in advanced technologies, such as microrobots, wearable electronic textiles, and implantable medical devices. They can be prepared with different carbon-based materials, but many devices suffer from low energy densities. Conformally loaded, Faradaically active CoAl-based layered double hydroxides (CoAl LDH) are loaded onto carbon fiber (CF) yarns to prepare supercapacitors with enhanced capacitance and energy density, avoiding the need for binding agents. The effect of different CoAl LDH loading amounts on morphological, structural, and electrochemical properties is studied, and a loading amount of 2.3 mg cm−2 is found to achieve the maximum specific capacitance of 634.3 F g−1 at a current density of 1 Ag−1. Flexible all-solid-state supercapacitor based on CoAl LDH@CF yarns offers excellent areal capacitance (195 mF cm−2) and volumetric energy density (1.6 mWh cm−3) with 94 % cyclic stability after 4000 galvanostatic charge–discharge (GCD) cycles. The energy density and flexibility of this CoAl LDH@CFs yarn-based all-solid-state supercapacitor offer great potential for energy management in flexible electronics.

CoMn LDH electrode is successfully prepared via facile and cost-effective electrodeposition method. The effect of Co 2+ /Mn 2+ molar ratio on supercapacitive performance is systematically investigated. It is found that the presence of Mn(OH) 6 unit in CoMn LDH offers an excellent reversibility as well as highly electrochemical activity for supercapacitor application. The CoMn LDH film with a Co 2+ /Mn 2+ molar ratio of 9:1 loaded on Ni foam electrode exhibits the maximum specific capacitance of 1062.6 F/g at the current density of 0.7 A/g with an excellent cyclic stability of 96.3% over 5000 CD cycles. It indicates that CoMn LDH nanoflakes loaded on Ni foam can minimize the lattice mismatch which leads to an excellent cyclic stability. The asymmetric supercapacitor assembled with CoMn LDH/Ni foam and AC electrodes shows an excellent cyclic life of 84.2% and an energy density of 4.4 Wh/kg with a power density of 2500 W/kg.

A novel electroactive Li+ ion-imprinted hybrid film consisting of λ-MnO2/PPy/PSS core–shell nanorods is successfully fabricated on an electrode by using the unipolar pulse electrodeposition (UPED) technique. When the electrode is applied for selective electrochemical extraction of low concentrations of Li+ ions from aqueous solutions via an electrochemically switched ion exchange (ESIX) process, the Li+ ion adsorption capacity reaches 35.2 mg g−1 with an adsorption equilibrium time of less than 2 h. The excellent ion separation performance of this hybrid film should be attributed to its low ion transfer resistance due to its porous structure and the high electric driving force during the ESIX process. In particular, owing to the unique Li+ ion imprinted vacant sites in the crystal structure of spinel λ-MnO2 nanorods, the selectivity factor for Li+/Na+ reaches 46.0 with a molar ratio of 1 : 1. It is expected that this λ-MnO2/PPy/PSS hybrid film can be applied as a promising electroactive material for effective separation of Li+ ions from seawater.