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Hydrogen production plays a major role in technologies for renewable energy storage. Water and urea electrolysis (WE, UE) are promising processes in this regard. The oxygen evolution reaction (OER) and urea oxidation reaction (UOR), respectively, are limiting the efficiency of the overall process. As catalysts for these reactions, metal-organic frameworks (MOF) have gained increasing attention due to their combinations and co-existence of metal and organic moiety properties. Here, we investigated the catalytic behavior of Ni MOF (1,3,5-Benzenetricarboxylic acid (BTC)) towards OER and UOR in alkaline medium on carbon paper (CP) as a support. The Ni MOF exhibits 346 mV overpotential (h) at a current density of 10 mA cm À2 , 79.03 A g À1 specific-mass activity at 400 mV of h than compared to wet chemically prepared (WCP) NiO and RuO 2 for OER in 1 M KOH. Meanwhile, % 230 mV of h at 10 mA cm À2 current density with appreciable stability for 12 hours for Ni MOF in 30 % KOH was also observed. For UOR in UE, Ni MOF shows an onset potential of 1.34 V vs. RHE and 63.15 mA cm À2 current density at 1.5 V vs RHE in 1 M KOH in the presence of 1 M urea. The observed results of OER and UOR catalytic behavior are better than wet chemically prepared (WCP) NiO and noble benchmark RuO 2 catalyst under identical conditions. The results suggested that the MOF plays a major role in enhancing the catalytic activity by the facile formation of Ni(OH) 2 /NiOOH, stability and electronic properties due to their porous and interconnected structure.

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A single step synthesized Co3O4–polyindole composite electrode exhibits high specific capacitance, rate performance and cyclability. This enhanced electrochemical supercapacitive behavior is mainly attributed to the synergistic effect between Co3O4 and polyindole.

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a b s t r a c tA novel synthetic approach has been designed to prepare CeO 2 /reduced graphene oxide (rGO) xerogel composite. The CeO 2 /rGO xerogel composite electrode displays much enhanced performance for the catalytic reduction of H 2 O 2 than the single component CeO 2 . The CeO 2 /rGO modified glassy carbon electrode displayed a wide linear range (60.7 nM-3.0 M), and low level of detection limit (30.40 nM) for H 2 O 2 and much higher sensitivity than that of CeO 2 nanoparticles modified electrode. The sensor fabricated by the xerogel composite was fast, stable, and reliable to the detection of hydrogen peroxide.

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The giant magnetoresistance (GMR) was investigated for electrodeposited Co/Cu multilayers. In order to better understand the formation of individual layers and their influence on GMR, multilayers produced by two different deposition strategies were compared. One series of Co(2 nm)/Cu(t Cu ) multilayers with t Cu ranging from 0.5 nm to 6 nm was produced with the conventional two-pulse plating by using a galvanostatic/potentiostatic (G/P) pulse combination for the magnetic/non-magnetic layer deposition, respectively, whereby the Cu layer deposition was carried out at the electrochemically optimized potential. Another Co(2 nm)/Cu(t Cu ) multilayer series with the same t Cu range was prepared with the help of a G/P/G pulse combination. In this latter case, first a bilayer of Co(2 nm)/Cu(6 nm) was deposited in each cycle as in the G/P mode after which a third G pulse was applied with a small anodic current to dissolve part of the 6 nm thick Cu layer in order to ensure the targeted t Cu value. The comparison of the two series revealed that the G/P/G pulse combination yields multilayers for which GMR can be obtained even at such low nominal Cu layer thicknesses where G/P multilayers already exhibit bulk-like anisotropic magnetoresistance only. Surface roughness measurements by atomic force microscopy revealed that the two kinds of pulse combination yield different surface roughness values which correlate with the structural quality of the multilayers as indicated by the absence or presence of multilayer satellite reflections in the X-ray diffraction patterns. A separation of the superparamagnetic (SPM) contribution from the total observed GMR provided useful hints at the understanding of differences in layer formation between samples prepared with the two kinds of pulse combination. The results of multilayer chemical analysis revealed that mainly an increased Cu content of the magnetic layer is responsible for the onset of SPM regions in the form of Co segregations in the G/P/G multilayers with small Cu layer thicknesses. Magnetization measurements provided coercive force and remanence data which gave further support for the above interpretation of the GMR data. The giant magnetoresistance (GMR) effect in electrodeposited (ED) multilayer films was extensively studied in the last two decades.