A novel electrochemical method for size-controlled synthesis of spherical silver nanoparticles in aqueous phase was developed for the first time. In this method the poly(N-vinylpyrrolidone) (PVP) was used as the stabilizer for the silver clusters. PVP was found to greatly promote silver particle formation rate and significantly reduce silver deposition rate, thereby making monodispersed silver nanoparticles to be synthesized very convenient by means of electroreduction of the bulk silver ions. It is possible to control the particle size by adjusting electrolysis parameters and to improve homogeneity of silver particles by changing the composition of electrolytic solutions. The results also showed the fact that the rate of transfer of PVP-stabilized silver clusters from the cathodic vicinity to the bulk solution played an important role in preparation of the monodispersed nanoparticles. In addition, the silver nanoparticles synthesized electrochemically may be directly employed to prepare the silver-doping tin electrodeposited coating.

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Graphitic carbons have been used as conductive supports for developing rechargeable batteries. However, the classic ion intercalation in graphitic carbon has yet to be coupled with extrinsic redox reactions to develop rechargeable batteries. Herein, we demonstrate the preparation of a free-standing, flexible nitrogen and phosphorus co-doped hierarchically porous graphitic carbon for iodine loading by pyrolysis of polyaniline coated cellulose wiper. We find that heteroatoms could provide additional defect sites for encapsulating iodine while the porous carbon skeleton facilitates redox reactions of iodine and ion intercalation. The combination of ion intercalation with redox reactions of iodine allows for developing rechargeable iodine–carbon batteries free from the unsafe lithium/sodium metals, and hence eliminates the long-standing safety issue. The unique architecture of the hierarchically porous graphitic carbon with heteroatom doping not only provides suitable spaces for both iodine encapsulation and cation intercalation but also generates efficient electronic and ionic transport pathways, thus leading to enhanced performance.

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The encapsulation of zinc hexacyanoferrate nanocubes with manganese oxide nanosheets enables the combination of intercalative core nanocube and capacitive shell together with reversible redox reactions for enhancing performance of Zn-ion batteries.

Several different types of equivalent circuits for the faradaic electrode process involving n state variables besides electrode potential are established in terms of the corresponding faradaic admittance equation in the case of ignoring mass transport. These circuits can develop into general equivalent circuits by introducing negative resistive and inductive and capacitive elements, each of which can be used to analyze any electrochemical impedance spectroscopy of the faradaic electrode process under electrochemical reaction control. The correspondence between element values of the circuits and electrochemical parameters of the faradaic admittance equation has also been determined by comparing the admittance or impedance of the equivalent circuit and the faradaic admittance or impedance equation. The use of general equivalent circuits, together with the faradaic admittance equation, greatly simplifies the analysis of electrochemical impedance spectroscopy for the faradaic electrode processes. © 1999 The Electrochemical Society. All rights reserved.

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Size-controlled Pd nanoparticles were electrochemically synthesized in large quantities at room temperature through the direct electroreduction of bulk PdCl4 2- ions in the presence of poly(N-vinylpyrrolidone) (PVP), a water-soluble polymer. The technological key to electrochemical synthesis of Pd particles is that PVP greatly promoted the formation process of Pd particles and inhibited the electrodeposition process of Pd onto the Pt cathode at the same time besides effectively stabilizing the formed Pd nanoparticles. The as-synthesized Pd nanoparticles display the voltammetric behavior significantly different from the bulk Pd and also present a high catalytic activity toward the electrooxidation of methanol.