Electrocatalysis of Ethanol and Methanol Electrooxidation by Composite Electrodes with NiOOH/FeOOH Supported on Reduced Graphene Oxide onto Composite Electrodes

This paper presents graphite/paraffin composite electrodes modified with microparticles of nickel (Ni) and Ni-Fe alloy anchored in reduced graphene oxide (rGO); these electrodes were made by electrosynthesis. Firstly, the electrodeposition of reduced graphene oxide was made by cyclic voltammetry (CV) onto the graphite/paraffin electrodes’ surface. After electrodeposition of the rGO, iron and nickel were electrodeposited by CV with successive scans. Finally, the formation of iron-nickel oxyhydroxide on the electrode surface was performed by cyclic voltammetry in alkaline medium. The composites were investigated by field emission gun scanning electron microscopy (FEG-SEM); it was observed that the Ni microparticles had spherical shapes, while the Ni-Fe alloy did not present a defined shape. The composite electrodes were used to analysis ethanol and methanol electrooxidation in an alkaline medium of 0.10 mol L−1 of NaOH in a potential range of from −0.20 to 1.0 V (vs. Ag/AgCl) at 50 mV s−1 by CV. The electrodes were able to make the electrooxidation of ethanol at a potential of around 0.57 V for the electrode constituted by the Ni-Fe alloy and around 0.61 V for the electrode modified with Ni, and for methanol in a potential around 0.57 V for the Ni-Fe alloy and around 0.66 V for the Ni electrode. The Ni-Fe alloy electrodes showed the electrocatalysis of the alcohols in relation to Ni electrodes.

Iron-Nickel Oxyhydroxide Catalyst from Watts Bath for the Oxygen Evolution Reaction in Water Electrolysis

A hydrogen economy is necessary to meet the social demands for less consumption of fossil fuels and it has several barriers that need to be addressed if this technology is to become cost effective. The oxygen evolution reaction (OER) is one of these barriers and catalysts based on nickel oxyhydroxide (NiOx) are believed to be promising for alkaline OER. We report results of iron doping for NiOx, we synthesized by electrodeposition, combinations of iron in Ni Watts solution to develop Fe- NiOx catalysts. The best sample has an overpotential of 254 mV at 10 mA cm-2 , this result is competitive to the best results found for alkaline OER. Our methodology consists of: linear and cyclic voltammetry, galvanostatic stability and electrochemical impedance spectroscopy as electrochemical techniques. In addition, physical catalyst characterization techniques include: scanning electron microscopy equipped with energy-dispersive X-ray spectroscopy, Raman spectroscopy and surface elemental analysis by wet chemistry.<br>

Iron-Nickel Oxyhydroxide Catalyst from Watts Bath for the Oxygen Evolution Reaction in Water Electrolysis

A hydrogen economy is necessary to meet the social demands for less consumption of fossil fuels and it has several barriers that need to be addressed if this technology is to become cost effective. The oxygen evolution reaction (OER) is one of these barriers and catalysts based on nickel oxyhydroxide (NiOx) are believed to be promising for alkaline OER. We report results of iron doping for NiOx, we synthesized by electrodeposition, combinations of iron in Ni Watts solution to develop Fe- NiOx catalysts. The best sample has an overpotential of 254 mV at 10 mA cm-2 , this result is competitive to the best results found for alkaline OER. Our methodology consists of: linear and cyclic voltammetry, galvanostatic stability and electrochemical impedance spectroscopy as electrochemical techniques. In addition, physical catalyst characterization techniques include: scanning electron microscopy equipped with energy-dispersive X-ray spectroscopy, Raman spectroscopy and surface elemental analysis by wet chemistry.<br>

Separating bulk and surface processes in NiOx electrocatalysts for water oxidation

Nickel oxyhydroxide electrocatalysts are highly active for water oxidation and swell when electrochemically activated. In this thickness dependence study, we find only the upper surface (<5 nm) is active during water oxidation catalysis.

Methanol, Ethanol, and Glycerol Oxidation by Graphite-Epoxy Composite Electrodes with Graphene-Anchored Nickel Oxyhydroxide Nanoparticles

In this work, a graphite-epoxy electrode with cyclic voltammetry electrodeposited reduced graphene oxide and nickel oxyhydroxide nanoparticles was prepared by decomposition in NaOH alkaline solution of cyclic voltammetry electrodeposited nickel hexacyanoferrate. FE-SEM studies were performed to confirm the NiOOH nanoparticle; the average size of the NiOOH nanoparticles was 61 ± 16 nm and EDX was applied to analyze chemical composition. To verify the performance of the prepared electrode, it was used in the electrooxidation of alcohols in alkaline medium by cyclic voltammetry. By performing different calibration experiments of methanol, ethanol, and glycerol, it was possible to extract some information about the electrode in the presence of alcohols. The LOD for methanol, ethanol, and glycerol were 2.16 mM, 2.73 mM and 0.09 mM, respectively, with sensitivity values of 1.32 µA mM−1, 1.80 µA mM−1 and 24.60 µA mM−1, respectively. Multivariate inspection of the data using Principal Component Analysis (performed with the ClustVis online tool) demonstrated the potential ability to discriminate between the different alcohols, whereas the explained variance with the first two components was as high as 89.7%.

Water Oxidation Catalysts from Waste Metal Resources: A Facile Metal-Organic Electrochemical Approach

A fabrication route is presented by a novel metal-organic electrochemical approach, allowing facile preparation of electrocatalytic metal and metal oxide thin films from solid metals at room temperature: divalent transition metals such as iron, nickel and cobalt can be deposited as amorphous oxyhydroxide films. Among them, nickel- and cobalt-prepared samples are showing high activity as water oxidation catalysts in alkaline electrolytes. The applicability to waste metal material is exemplified using one of the most abundant waste metal alloys, i.e. steel: with a suitable multi-layer architecture, comprising, a large surface-area iron oxyhydroxide core-geometry and a steel-derived catalytic overlayer, the overpotential for oxygen evolution (at 10 mA cm−2) could be improved to only 370 mV. Chemical analysis is provided to elucidate the reaction pathway, encompassing metal halogenation, formation of meta-stable metal-organic intermediates or direct electrochemical reduction, respectively. Structural peculiarities of the derived films are finally demonstrated upon development of a photoactive nickel oxyhydroxide/silicon junction realizing a photocurrent of 1 mA cm−2 at the thermodynamic potential for oxygen evolution and short-term stabilization in the range of several hours.