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An advanced oxidation process of ultrasound/MnFe2O4/K2S2O8 was developed for the degradation of diazine dye safranin T, according to which potassium persulfate was coactivated by ultrasonic (US) cavitation and MnFe2O4 spinel nanoparticles synthesized via co-precipitation in the ultrasonic field. A synthesis product annealed at a temperature of 4000 C, with an average size of MnFe2O4 crystallites of about 7 nm, was used as a catalyst for the decomposition of potassium persulfate. Based on the results of experimental studies on the influence of various factors on the degree and rate constant of safranin T oxidative degradation, as well as considering energy and resource-saving principles, the rational conditions of oxidative degradation were determined as follows: the reaction medium temperature of 600 C, the molar ratio of safranin T:K2S2O8=1:100, the catalyst loading of 0.1 g/l, and the specific power of the ultrasonic cavitation treatment of 51.0 W/l. It was established that under such conditions the oxidative degradation degree of safranin T was equal to 98.3%, and the rate constant was 1.5⋅10–3 s–1. The changes in the UV-Vis spectra of safranin T, namely a decrease in the intensity of absorption bands, both in the visible (at a wavelength of 520 nm) and in the UV (at a wavelength of 275 nm) regions of the spectrum, confirmed the degradation of safranin T. In addition, the absence of the appearance of new peaks in the visible and UV regions of the spectrum indicated mineralization of the dye. [ABSTRACT FROM AUTHOR]

The rates of the CO2 electrochemical induction were determined on porous cathodes formed by electrochemical dealloying of CuZn under different regimes of selective anodic dezincification of brass. It was established that the formation of a porous surface proceeds in two following stages: 1) the dissolution of Zn from the CuZn mainly along the grain boundaries with the formation of submicron crevices between them, and 2) electrochemical dezincification of brass grains and formation of nanopores. The zinc content in the nan op or ole copper surface is less than 1%. It was proved that anodically dezincified brass porous cathodes demonstrate a significantly higher CO2 reduction current on their surface than smooth copper and brass surfaces. For instance, in aqueous solutions, at an electrode potential of-1.5 V, the value of cathode current density on porous Cu cathodes is between 5 to 9 mAcm-1, while it is only 2.5 and 1.5 mAcm-2 on smooth Cu and CuZn cathodes, respectively. A similar trend is observed in an acetonitrile environment, where the current density of the CO2 electroreduction at the electrode potential of -3.0 Vis 22 to 27 mAcm-2, k15 mAcm-2, and k1

Sedimentation of gold on a copper surface via galvanic replacement (GR) method from (1–4)mM H[AuCl4] + 50 mM Bu4NClO4 solutions in DMF has been studied. It is shown that copper surface decoration (Cu + Au) occurs with the formation of Au nanofilms fragments (0.5 Wt%) and almost solid Au nanofilm (≥ 3.6 Wt%). The main factors influencing the controlled gold content on the copper surface are the concentration of H[AuCl4] and temperature. It was found that the reduction of CO2 on (Cu + Au) cathodes in DMF solutions occurs at higher current values compared to copper ones, and the cathode currents increases with increasing Au content. Thus, at E = − 3.0 V, icathode = 10.9, 11.2 and 17.0 mA⋅cm−2 at Au content of 0.5, 0.8 and 3.6 Wt%, while on copper cathodes icathode = 6.0 mA⋅cm−2. [ABSTRACT FROM AUTHOR]

The dependency of CO2 reduction rate in acetonitrile-Bu4NClO4 solution on cathodes, which were modified by laser induction of a copper surface, was studied. The topography of laser-induced periodic surface structures (LIPSS) → grooves → spikes was successively formed by a certain number of pulses. It was proved that for a higher number of laser pulses, the surface area of the copper cathode increases and preferred platy orientation of the copper surface on [022] crystallografic direction and larger fluence values increase. At the same time, the content of copper (I) oxide on the surface of the copper cathode increases. Also, the tendency to larger fluency values is observed. It promotes the increase of cathodic current density for CO2 reduction, which reaches values of 14 mA cm-2 for samples with spikes surface structures at E = − 3.0 V upon a stable process. [ABSTRACT FROM AUTHOR]

The deposition processes of nanosized particles of silver, palladium and gold on the silicon surface by galvanic replacement in fluoride-containing solutions of AgNO3 in DMF, Pd(NO3)2, and H[AuCl4] in DMSO in an ultrasonic field are studied. The influence of the ultrasonic field on the geometry of metal particles and the morphology of precipitate on the substrate is described. It is shown that ultrasonication of (1–10) mM AgNO3 solutions in DMF promotes the formation of nanostructured films on the silicon surface. The tendency to the nanofilms formation is also observed for gold. It was found that ultrasonication allows the deposition of gold on silicon by galvanic replacement in fluoride-free solutions of H[AuCl4]. An increase of the temperature of the solution causes the formation of dispersed precipitates on the silicon surface and an increase of the particles size. [ABSTRACT FROM AUTHOR]

An annual increase of CO2 concentrations in the atmosphere causes global environmental problems, addressed by systematic research to develop effective technologies for capturing and utilizing carbon dioxide. Electrochemical catalytic reduction is one of the effective directions of CO2 conversion into valuable chemicals and fuels. The electrochemical conversion of CO2 at catalytically active electrodes in aqueous solutions is the most studied. However, the problems of low selectivity for target products and hydrogen evolution are unresolved. Literature sources on CO2 reduction at catalytically active cathodes in nonaqueous mediums, particularly in organic aprotic solvents, are analyzed in this article. Two directions of cathodic reduction of CO2 are considered—nonaqueous organic aprotic solvents and organic aprotic solvents containing water. The current interpretation of the cathodic conversion mechanism of carbon (IV) oxide into CO and organic products and the main factors influencing the rate of CO2 reduction, Faradaic efficiency of conversion products, and the ratio of direct cathodic reduction of CO2 are given. The influence of the nature of organic aprotic solvent is analyzed, including the topography of the catalytically active cathode, values of cathode potential, and temperature. Emphasis is placed on the role of water impurities in reducing CO2 electroreduction overpotentials and the formation of new CO2 conversion products, including formate and H2. [ABSTRACT FROM AUTHOR]