Electrodeposition of nickel on vitreous carbon: Influence of potential on deposit morphology

The Electrochemical Oxidation and Mass Transfer Mechanism of Formic Acid on the Catalyst Electrode Surface

The organic small molecule fuel battery has attracted wild attention in recent years. Unfortunately, the inherent catalyst poisoning phenomenon hinders its commercialization. Exploring the anodic catalytic reaction mechanism is urgent. This article investigates the nucleation mechanism of HCOOH on the catalyst electrode surface. The electrochemical results indicate that the HCOOH oxidation conforms to the two-dimensional instantaneous nucleation process. The corresponding adsorption model of CO on the catalyst surface was finally established.

Ultramicroelectrode Studies of Self-Terminated Nickel Electrodeposition and Nickel Hydroxide Formation upon Water Reduction

The interaction between electrodeposition of Ni and electrolyte breakdown, namely the hydrogen evolution reaction (HER) via H₃O⁺ and H₂O reduction, was investigated under well-defined mass transport conditions using ultramicroelectrodes (UME's) coupled with optical imaging, generation/collection scanning electrochemical microscopy (G/C-SECM), and preliminary microscale pH measurements. For 5 mmol/L NiCl₂ + 0.1 mol/L NaCl, pH 3.0, electrolytes, the voltammetric current at modest overpotentials, i.e., between -0.6 V and -1.4 V vs. Ag/AgCl, was distributed between metal deposition and H₃O⁺ reduction, with both reactions reaching mass transport limited current values. At more negative potentials, an unusual sharp current spike appeared upon the onset of H₂O reduction that was accompanied by a transient increase in H₂ production. The peak potential of the current spike was a function of both [Ni(H₂O)₆]²⁺_(aq) concentration and pH. The sharp rise in current was ascribed to the onset of autocatalytic H₂O reduction, where electrochemically generated OH^- species induce heterogeneous nucleation of Ni(OH)_2(ads) islands, the perimeter of which is reportedly active for H₂O reduction. As the layer coalesces, further metal deposition is quenched while H₂O reduction continues albeit at a decreased rate as fewer of the most reactive sites, e.g., Ni/Ni(OH)₂ island edges, are available. At potentials below -1.5 V vs. Ag/AgCl, H₂O reduction is accelerated, leading to homogeneous precipitation of bulk Ni(OH)₂·xH₂O within the nearly hemispherical diffusion layer of the UME.

Electrodeposition and characterization of Ni–SiC composite coatings from deep eutectic solvent

The micro or nano-sized SiC particles have significant effects on nucleation/growth process, morphology, microhardness and trilogical performance of Ni coatings.