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Zinc is recently gaining interest in the battery community as potential alternative anode material, because of its large natural abundance and potentially larger volumetric density than graphite. Nevertheless, pure Zn anodes have shown so far very poor cycling performance. Here, the electrochemical performance of Zn‐rich porous Cu–Zn alloys electrodeposited by an environmentally friendly (aqueous) dynamic hydrogen bubble template method is reported. The lithiation/delithiation mechanism is studied in detail by both in situ and ex situ X‐ray diffraction, indicating the reversible displacement of Zn from the Cu–Zn alloy upon reaction with Li. The influence of the alloy composition on the performance of carbon‐ and binder‐free electrodes is also investigated. The optimal Cu:Zn atomic ratio is found to be 18:82, which provides impressive rate capability up to 10 A g−1 (≈30C), and promising capacity retention upon more than 500 cycles. The high electronic conductivity provided by Cu, and the porous electrode morphology also enable superior lithium storage capability at low temperature. Cu18Zn82 can indeed steadily deliver ≈200 mAh g−1 at −20 °C, whereas an analogous commercial graphite electrode rapidly fades to only 12 mAh g−1.

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Cu-Ni alloy layers with a bimodal porosity -a spongy material made of submicron dendrites, featuring macroscopic pores tens of microns large -can be deposited from baths containing the metal ions, sodium citrate and ammonium sulfate, using large current densities (−3 A cm −2 ) producing vigorous hydrogen evolution. Alloys with a broad range of compositions are obtained using baths with different Cu(II)/Ni(II) concentration ratios. Voltammetric experiments of nitrate reduction at compact and porous Cu-Ni RDEs show, in the latter case, lower overvoltage and higher peak currents, resulting from enhanced transport and improved catalytic activity. © 2013 The Electrochemical Society. [DOI: 10.1149/2.004311eel] All rights reserved.Manuscript submitted July 18, 2013; revised manuscript received August 6, 2013. Published August 21, 2013 Porous electrodes are a topic of intense current interest.1-13 Among the traditional preparation methods, dealloying is applicable only in a few cases and the final materials contain inclusions of the less noble metal.1,2 Modern approaches based on electrodeposition within rigid templates 3 -based e.g. on polymers, 4,5 silica spheres, 6 alumina membranes 7 -warrant a good control of shape, size and organization of the inner porosity, but require final removal of the template and usually provide uniform tiny porosity that may not improve electrode performances in diffusion controlled processes. 6A convenient alternative procedure is deposition in presence of copious hydrogen evolution: the gas bubbles act as a dynamic, faint template that disappears after switching off the current and allows a single step preparation. The method has been tested for the deposition of several porous metals including Sn, 8 Cu, [8][9][10]11,12 Ag and Au 13and typically results in a bimodal porosity of potential interest in electrocatalysis, as the tiny structures with dimensions down to tens of nanometers provide a large surface area, while macropores tens of microns large may ensure enhanced mass transport. The extension of this approach to deposition of porous alloys of controlled composition is not obvious and only a few cases have been described. 14,15 We have recently reported on the deposition of compact Cu-Ni alloys with a large range of compositions and on their strong activity in nitrate reduction. 16 We propose in this paper the deposition of porous Cu-Ni electrodes that show improved characteristics in this reaction and that might provide, at low cost, a good electrode material in applications like wastewater treatment and electroanalysis. 17 ExperimentalThe single compartment cell used for deposition was equipped with a Pt wire counter electrode wound as a spiral around the inner wall. RDE electrodes were obtained from Cu rods (Goodfellow, 99.999% purity), or Nb rods (Goodfellow, 99.9%) inserted in a PTFE sheath; their geometric area was 0.317 cm 2 and 0.247 cm 2 , respectively. Nb RDEs were used for EDS analyses, Nb sheets (Goodfellow, 99.5%) for deposition of samples devoted to XRD analyses. All ...