Andrzej Kowal

Nickel hydroxide electrocatalysts for alcohol oxidation reactions: An evaluation by infrared spectroscopy and electrochemical methods

Abstract We have investigated the electrochemical oxidation of four alcohols (methanol, 1-, 2- and tertiary butanol) at Ni hydroxide electrodes in alkaline electrolytes. In situ FTIR spectroscopy and electrochemical methods have been used to examine these oxidation reactions. Oxidation of the primary and secondary alcohols commences in the potential region where it is proposed that multi-layers of NiOOH are formed on the electrode surface; while no reaction occurs with tertiary butanol. Methanol oxidation occurs in two stages, with predominantly formate being formed in the potential window 0.36-0.44 V (vs. SCE), followed by further oxidation to carbonate at potentials above approx. 0.45 V. Butanoate is the only detected reaction product for 1-butanol electrooxidation in the potential range 0.36-0.5 V. The oxidation of 2-butanol is more complex. In the lower potential range (0.36-0.44 V) the major reaction product is butanone, which is further oxidised at higher potentials to either acetate or a mixture of propanoate and formate (or carbonate). In addition, rate constants have been determined for the first stage of the electrochemical oxidation of all the alcohols investigated.

Noble metal (Ag, Au) cementation on non-stoichiometric cuprous sulphide grains

Noble metal cementation on Cu2−xS grains was studied by measuring the concentration of Ag+ (or AuCl4−) ions in the solution circulating in a special apparatus containing sample of grains. The rate of the cementation process was determined as a function of the reaction extent, which was equivalent to the deposition of approximately 50 uniform atomic layers of the noble metal on the grains surfaces. Changes in the surface microstructure and composition of the samples were determined using X-ray diffraction (XRD), scanning electron microscopy (SEM/EDS) and atomic force microscopy (AFM). Different surface products: mixed copper–silver sulphides, gold sulphides and gold crystallites were found, depending on nature of the noble metal and the solution composition. The course of cementation of gold was greatly changed using chloride instead of sulphate ions. The notable change of the process rate is ascribed to the greatly different structure of gold cementation products on Cu2−xS, as found by the analysis techniques: XRD, SEM and AFM, respectively.

The Study of Nickel Hydroxide Catalyst Surface During Organic Electrosynthesis by Atomic Force Microscopy

Oxidation of alcohols on nickel hydroxide electrodes has been studied for twenty years. The mechanism of the oxidation reaction was proposed by Pletcher and Fleishmann [1] and extended by Schafer[2]. Recently Kowal and coworkers used the modern in-situ methods for understanding the mechanism of the oxidation reaction [3] and the stability of nickel hydroxide electrodes [4,5].

Electrochemical Oxidation of Alcohol with Nickel Hydroxide Electrocatalyst Studied by the in Situ Techniques: Infrared Spectroscopy, Potential Modulated Reflectance Spectroscopy and Electrochemical Methods. An Attempt for Electrooganic Synthesis of Organic Acids

Both the organic phase and catalyst surface were monitored in situ during the electrochemical synthesis by just using two types of radiation. To monitor the organic phase we use infrared radiation [1], and to examine the catalyst surface we use UV-VIS radiation (320-800 nm) [2].