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Herein, we report a hybrid electrocatalyst consisting of Ru clusters trapped in NiCo-layered double hydroxide (NiCo-LDH) as the basis for an efficient hydrogen evolution reaction (HER) in alkaline media. Benefiting from the fast water dissociation kinetics on NiCo-LDH and favorable H recombination on Ru, the resultant Ru-NiCo-LDH shows an extremely low HER overpotential of 28 mV at a current density of 10 mA cm−2 with a small Tafel slope of 42 mV dec−1. This superior catalytic activity can be ascribed to its high charge transfer ability and to the synergistic effect of the highly dispersed Ru and the NiCo-LDH. Moreover, we also found that the oxidized Ru incorporated in NiCo-LDH was entirely reduced to Ru0 under hydrogen-evolution conditions, which suggests that Ru0 is the true catalytically active phase responsible for the outstanding HER performance. Keywords: Ruthenium, NiCo-layered double hydroxide, Hydrogen evolution reaction, Water dissociation

In this work, defect-engineered carbon nanotube networks are grown in situ on a 316L stainless steel substrate using chemical vapor deposition and an annealing treatment. The defective carbon nanotube networks can be applied directly as electrodes for the simultaneous determination of ascorbic acid and uric acid using cyclic voltammetry and differential pulse voltammetry. Carbon nanotube networks annealed at 500 °C enable simultaneous determination of ascorbic acid and uric acid with linear responses from 100 to 3000 μM and from 10 to 150 μM, respectively. The excellent electrocatalytic activity of the defective carbon nanotube networks is attributed to the engineered defects and the large number of exposed edge planes. Keywords: Carbon nanotube networks, 316L stainless steel, Electrochemical electrodes, Ascorbic acid, Uric acid

The use of Ni-based oxides/hydroxides in the oxygen evolution reaction has been extensively reported and fluoride precursors have frequently been used in their synthesis. However, there have been no studies of the effect of fluoride in Ni-based oxides/hydroxides on the hydrogen evolution reaction (HER) as these materials are generally considered inactive for HER. Recently the HER activities of Ni-based oxides/hydroxides have been improved by doping with anions (P, S, and Se). However, these compounds are chemically unstable during HER and can be converted into the corresponding oxides/hydroxides. In this paper we discovered an interesting phenomenon: the NiFe hydroxide can be turned into an active HER material by incorporating fluoride into it. In 1M KOH, a significant shift of ~91mV was observed in the HER overpotential at −10mA/cm2 due to the enhanced charge transfer ability triggered by fluoride. This discovery provides a new approach to turning normally inactive materials, whose catalytic activity is hindered by low intrinsic conductivity, into electrocatalysts, and will lead to the discovery of new catalysts. Keywords: Ni-based hydroxide, Hydrogen evolution, Fluoride incorporation, Charge transfer, Electrocatalysis

Herein, we report a scalable strategy to fabricate a film of 3D multilayer graphene platelets by the carbonization of a polydopamine coating on a template of an aligned nanopore array formed by the electrochemical anodization on a stainless steel surface. The 3D graphene platelets possess a large number of exposed edge planes on the open ends as well as inner walls of the nanopores. The simultaneous voltammetric determination of uric acid (UA) and ascorbic acid (AA) has been demonstrated at the 3D multilayer graphene platelet film, with linear ranges of 50–2000 μM for AA and 5–500 μM for UA. Amperometric detection of dopamine illustrates a linear response in the range of 1–272 μM and a detection limit of 0.02 μM (S/N = 3). Keywords: Three dimensional multilayer graphene platelets, Polydopamine coating, Graphitic edge-planes, Uric acid, Ascorbic acid, Dopamine

Ordered mushroom-like hybrid CuO/Pt/Si nanoarrays were fabricated using ion etching followed by the electrochemical method. The process started with patterning the surface of a Si (100) substrate coated with a thin layer of Pt, forming a hybrid array of nanoneedles. Each nanoneedle consists of a Pt nanodot sitting on top of a Si nanorod. Cu nanosphere was subsequently grown on the surface of each Pt dot and then oxidized to CuO by the method of continuous cyclic voltammetry in NaOH solution. Meanwhile, the multiple redox cycles produce a rough and porous surface on these CuO nanospheres, which significantly increases the contact area of the nanosphere surfaces with the external environments. This unique nanostructure array shows excellent electrochemical sensitivity to glucose detection. Keywords: Electrodeposition, Hybrid nanoarray, CuO, Glucose detection

In the present paper, a method has been successfully developed to prepare the copper needles. These needles have sufficiently thin tip regions that allow the direct TEM observation of the oxide layers grown on the surface of copper subjected to the electrochemical oxidation in the aqueous solution at nano-scale. The results show that the duplex layers are formed on the copper surface in the alkaline solution during electrochemical polarization and the layer growth follows a sequential order. An impact inner layer consisting of Cu2O is first formed at low anodic potentials, which will be then transformed into CuO when the anodic potentials increase before the occurrence of oxygen evolution. Subsequently, the production of Cu(OH)2 on the top of CuO inner layer leads to the formation of the outer layer. The epitaxial orientation relationship between the inner oxide layer and its adjacent copper matrix is discovered. The outer oxide layer appears porous consisting of nano-crystals. Some nano-crystals are oriented well with the inner layer due to their direct growth from it. The rest randomly-oriented nano-crystals are produced by the dissolution of oxides into the solution forming copper hydroxide particles, which are immediately deposited back to the surface of the copper needle. Keywords: Copper, Electrochemical oxidation, Transmission electron microscopy (TEM), Nano-scale, Alkaline solution