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To further enhance the long-term durability of the cost-effective Ir-based catalysts, some acid-stable oxides are used as supports for acidic OER catalysts. Herein, taking carbon paper (CP) as the substrate, we prepared a self-standing IrW/WO 3-x @NC/CP electrode via a layer-by-layer modified method. Among it, N-doped porous C framework not only provides a large specific surface for the attachment of WO 3-x , but also makes up for the lack of conductivity of WO 3-x and accelerates the electron transport process. The interaction between Ir and W sites in the form of IrW alloy which has generated during the high-temperature calcination and the dispersed Ir in WO 3-x matrix improve the intrinsic catalytic activity. And due to the Pt-like effect of W and the tuning role of the electronic structure by the IrW alloy, IrW/WO 3-x @NC/CP with an Ir content of only 19.1 µg cm−2 exhibits excellent bifunctional activity in acidic media. To obtain 10 mA cm−2, IrW/WO 3-x @NC/CP just needs overpotential of 22 mV (for HER) and 206 mV (for OER) respectively with a mass specific activity of 4.008 A mg Ir −1 at 1.55 V. For the whole water splitting, it only requires 1.52 V and 1.70 V to reach 10 mA cm−2 and 100 mA cm−2 respectively, and can operate continuously for over 40 h. [ABSTRACT FROM AUTHOR]

This paper describes the electrochemical behaviour of self-assembled monolayers (SAMs) of n-alkanethiolates with Fc groups inserted at 14 different positions along the alkyl chain (SC n FcC 13-n , n = 0–13) studied by cyclic voltammetry. The electronic and supramolecular structures of the SAMs have been fully characterised and all molecules are standing up, allowing for precise control over the position of the Fc unit within the SAM as a function of n revealing the shape of the electrostatic potential profile across the SAMs. The potential profile is highly non-linear due to electronic changes in the nature of the Fc—electrode interaction for small values of n < 5, and supramolecular changes for large values of n = 11–13. For intermediate values of n = 5–11, the potential drop is linear and the data can be fitted to a model developed by White and Smith. The electrochemical behaviour was dominated by a one-step reversible redox-process, but the presence of a shoulder indicates that the Fc units are present in different microenvironments resulting from the mismatch in size between the Fc units and the alkyl chains. Other features, including peak splitting, peak broadening, and peak shifts, can be related to changes in the electronic and supramolecular structure of the SAM revealed by molecular dynamics simulations and spectroscopy. For small values of n < 5, electronic effects dominate and the peak oxidation waves are shifted anodically (∼150 mV) and broadened (full width at half maximum of up to 220 mV) because the Fc units hybridise with the Au electrode (for n < 3) or interact with the Au electrode via van der Waals interactions (n = 4, 5). For intermediate values of n = 5–11, supramolecular effects direct the packing structure of the SAMs and clear odd-even effects are observed. For large values of n = 11–13, the top alkyl chains are liquid-like in character and do not block the Fc units from the electrolyte. [ABSTRACT FROM AUTHOR]

This paper studies the electronic structures of the 14 flavonoids and their cation and radical forms involved in the first electrochemical oxidation step, associated with the oxidation peak appearing at potential E p1 . The sum of differences in Net atomic charges on atoms in skeleton of cations and neutral flavonoids ( Σ s ( C ) ΔNAC Cat.-Neut. ) and the sum of Atomic orbital electron and spin populations on atoms in skeleton of radicals ( Σ s ( C ) AOEP and Σ s ( C ) AOSP) revealed that electron distribution between skeleton atoms and active OH oxygen is more evenly distributed in cations and radicals of flavonoids that are more prone to oxidation. Those less susceptible to oxidation are more polarized, i.e. the skeleton becomes more positively charged. Also, Σ s ( C ) AOSP proved to be an excellent descriptor for modelling the first oxidation potential, especially in combination with Σ s ( C ) p z AOEP (common model for pH = 3 and 7 yielded R 2  = 0.978 and S.E. = 0.43). [ABSTRACT FROM AUTHOR]

The performance of TiO 2 nanosheets (TiO 2 -NSs) modified carbon paper anode (TiO 2 -NSs/CP) in S. loihica PV-4 inoculated MFCs is greatly improved by intentional N doping of TiO 2 -NSs to modulate its electronic properties. TiO 2 -NSs/CP is calcined in NH 3 atmosphere at different temperatures (T = 400, 500, 600 and 700 °C) to obtain N doped anodes (T-NTiO 2 -NSs/CP, T represents temperature), in which 600-NTiO 2 -NSs/CP electrode show best performance with the maximum output power density increased by 196% and 50% compared to that from the bare CP and TiO 2 -NSs/CP electrodes respectively. The surface morphology, structure and electrochemical activity are characterized by FESEM, XRD, Raman, XPS, CVs and EIS. The results show that heating in NH 3 atmosphere keep surface morphology and bio-affinity of the electrode. The midpoint potential E m (−0.29 V) of outer membrane c-type cytochromes (OMCs) at 600-NTiO 2 -NSs/CP anode is in accordance with that at TiO 2 -NSs/CP. However, 600-NTiO 2 -NSs/CP electrode had smaller charge transfer resistance, more positive flat-band potential and larger transient charge storage capacity than untreated electrode due to modulation of the electronic structure via N doping, which all are favorable to interfacial electron transfer from OMCs to underlying electrode. The method is simply and efficient, and could be extended to other nano-semiconductor modified electrodes for superior MFC anodes. [ABSTRACT FROM AUTHOR]

• Systematic study of 3d transition metal-doped CNTs. • V(Cr, Mn, Co)-doped CNTs show spin-polarization effects. • The 3d transition metal doping makes a big difference to the energy band. • 3d transition metal doping increases the quantum capacitance. • Ni-CNT has the largest quantum capacitance near zero potential. Supercapacitors are valued as one of the new green energy storage devices, but the low energy density limits the wide application of supercapacitors. In this paper, the effects of 3d transition metal doped on electronic structure and quantum capacitance of carbon nanotubes are investigated using DFT. The calculations show that elemental doping has caused the break-up of two degenerate states near the Fermi level, quasi-local state changes in the energy band, and the creation of new energy bands. The doping of V(Cr, Mn, Co) causes spin polarization in the energy band. The change in energy band affects the density of states near the Fermi level, effectively increasing the quantum capacitance and surface charge density of the carbon nanotube electrode. The quantum capacitance of Ni-doped carbon nanotubes is the largest, at 59.74 µF/cm2. In the range of water stability, Ti(V, Gr, Mn, Co)-CNT are suitable for use as electrode materials in symmetrical double layer supercapacitors. Sc(Fe, Cu, Zn)-CNT is suitable for use as anode materials in asymmetric double layer supercapacitors. Ni-CNT is suitable for use as a cathode material for asymmetric double layer supercapacitors. This study verifies the feasibility of 3d transition metal doping to improve the quantum capacitance of carbon nanotube electrodes. [Display omitted] [ABSTRACT FROM AUTHOR]

In this paper, a series of Li 3-x Na x V 2 (PO 4 ) 3 (0 ≤ x ≤ 3) are prepared by a solid state reaction and systematically evaluated as anode materials for lithium-ion batteries. Structural analysis shows that the phase structure of Li 3-x Na x V 2 (PO 4 ) 3 changes along with the evolution of Na content. Charge-discharge tests exhibit that Li 3 V 2 (PO 4 ) 3 shows the highest initial charge specific capacity as high as 88.3 mAh g −1 among all the seven samples, and the reversible capacity is kept at 68.3 mAh g −1 after 45 cycles, corresponding to 77.3% of the initial charge capacity. With increasing of Na content in Li 3-x Na x V 2 (PO 4 ) 3 , the as-obtained sample show poorer lithium storage capability than Li 3 V 2 (PO 4 ) 3 . As a result, Na 3 V 2 (PO 4 ) 3 shows the inferior cycling performance than other Li 3-x Na x V 2 (PO 4 ) 3 . It can only deliver a reversible capacity of 20.9 mAh g −1 after 45 cycles, corresponding to 45.9% of the initial charge capacity. In-situ X-ray diffraction observations demonstrate that the poor electrochemical property of Na 3 V 2 (PO 4 ) 3 anode is due to the irreversible structural evolution during charge-discharge process. Therefore, reducing the Na 3 V 2 (PO 4 ) 3 phase in as-obtained sample is a feasible route to improve the lithium storage capability of Li 3-x Na x V 2 (PO 4 ) 3 . [ABSTRACT FROM AUTHOR]

• Full characterization of NiII( tpa ) complexes gives information about its electronic structure which corelates with electrochemical behavior. • NiII( tpa ) complexes presented tunable redox potential for the NiII/NiI reduction. • NiII complex with more negative redox potential presented the high catalytic activity for CO 2 reduction. • Theoretical approach was useful for the analysis and description of electrochemical mechanisms. In this paper, we report the synthesis, characterization, as well as electrochemical, spectroelectrochemical, and density functional theory (DFT) calculations of a series of novel NiII complexes with a flexible tetradentate ligand, tris(2-pyridylmethyl)amine) ( tpa ). The complexes [NiII( tpa )(H 2 O)(MeCN)](BF 4) 2 , [NiII( tpa )(NO 3) 2 ], and [NiII( tpa )Cl 2 ] were studied for their ability to electrochemically reduce CO 2. These complexes were compared with the tris-chelate complex [Ni(bpy) 3 ](BF 4) 2 to understand the role of flexible tetradentate ligands containing a pyridinic ring in the electrochemical reduction of CO 2. Spectroelectrochemical experiments and theoretical studies were performed to rationalize the electrochemical reductions occurring and to predict the redox potential and pathway of CO 2 reduction. The electrochemical behavior of Ni(II) complexes with the ligand tris(2-pyridylmethyl)amine) was studied, in order to explore its ability to reduce electrochemically CO 2. Theoretical studies allowed to rationalize where the electrochemical reductions occur and predict redox potential and the pathway of CO 2 reduction. [Display omitted] [ABSTRACT FROM AUTHOR]

Conductive CoS 2 and cycling stable MoS 2 are integrated to form the interconnected CoS 2 /MoS 2 nanosheet composite with electroactive interface grown on Mo foil substrate to act as high-performance supercapacitor anode material with electrochemical and mechanical stability. The band gap and density of state of CoS 2 /MoS 2 determined by density functional theory simulation calculation indicates its improved electrical conductivity. The interface binding energy and differential charge density reveal that strong crystal interface interaction between MoS 2 (002) and CoS 2 (111) enables effective charge transfer in interconnected CoS 2 /MoS 2 nanosheet composite. CoS 2 /MoS 2 exhibits higher specific capacitance of 605.77 mF cm−2 than MoS 2 of 218.1 mF cm−2 at 1.0 mA cm−2 in 0.5 M Na 2 SO 4. The rate capacitance retention is improved from 57.8% of MoS 2 to 82.8% of CoS 2 /MoS 2 at 1–10 mA cm−2. The high cycling stability is achieved for MoS 2 (100.2%) and CoS 2 /MoS 2 (104.05%) after 5000 cycles at 10 mA cm−2 due to self-activation of multilayered MoS 2. An asymmetric solid-state supercapacitor using CoS 2 /MoS 2 anode and MnO 2 /carbon paper cathode achieves a capacitance of 4.32 F cm−3 at 1.0 mA cm−2 and an energy density of 1.944 mWh cm−3 at a power density of 18 mW cm−3, 97.8% after 5000 cycles at 5.0 mA cm−2, presenting effective energy storage. [ABSTRACT FROM AUTHOR]

Molybdenum disulfide (MoS 2) is one of the promising candidates for hydrogen evolution reaction (HER), it's HER properties can be extremely enhanced by the construction of nanostructure and the regulation of electronic structure. In this paper, hierarchical composites with MoS 2 and carbon nanotubes (CNTs) as the noble metal-free electrocatalysts for HER were fabricated through calcination and hydrothermal processes, in which the MoS 2 nanosheets with Ni atoms incorporation were vertically grown on the outsides of nitrogen (N)-doped CNTs. The constructed hierarchical structures provide large specific surface area of about 150 m2 g−1 and high structure stability. Importantly, the MoS 2 nanosheets with enlarged interlayer spacing possess ultrathin structure of about 4 nm in thickness. Owing to the incorporation of Ni atoms, abundant unsaturated S atoms are obtained in the basal plane, which leading to more active sites exposed during HER processes. Meanwhile, N-doped CNTs can act as the substrate for MoS 2 nanosheets growing and simultaneously improve the conductivity of catalyst. Based on the synergy of hierarchical structure, increased active sites and enhanced conductivity, the as-prepared electrocatalysts exhibit superior HER activity with low overpotentials, small Tafel slopes and long-time durability in both acidic and alkaline electrolytes. The overpotentials of 158 and 179 mV were required to drive HER current density up to 10 mA cm−2 in 0.5 M H 2 SO 4 and 1.0 M KOH, respectively. This work reports a highly efficient MoS 2 -based electrocatalyst for HER via fabricating hierarchical structure and doping Ni atoms. Image 1 [ABSTRACT FROM AUTHOR]