Water-Based Electrophoretic Deposition of Ternary Cobalt-Nickel-Iron Oxides on AISI304 Stainless Steel for Oxygen Evolution

Coatings consisting of cobalt, nickel and iron (Co-Ni-Fe) oxides were electrophoretically deposited on AISI 304-type stainless steel using aqueous suspensions without any binder. The synthesis of Co-Ni-Fe oxides was carried out by the thermal decomposition of metal nitrates with various molar ratios at 673 K. Structural and morphological analysis confirmed that the deposited coatings were mainly composed of spinel-type oxides with predominantly round-shaped particles. The prepared electrodes were examined for their electrocatalytic performance in oxygen generation under alkaline conditions. Various electrochemical techniques indicated the influence of iron content on the electrochemical activity of Co-Ni-Fe oxides, with the calculated values of the Tafel constant being in the range of 52–59 mV dec−1. Long-term oxygen generation for 24 h at 1.0 V revealed very good mechanical and electrocatalytic stability of the prepared electrodes, since they were able to maintain up to 98% of their initial activity.

Improving sono-activated persulfate oxidation using mechanical mixing in a 35-kHz ultrasonic reactor: Persulfate activation mechanism and its application

This study investigated the degradation of ibuprofen (IBP), an activated persulfate (PS), when subjected to ultrasonic (US) irradiation and mechanical mixing (M). The effects of several critical factors were evaluated, including the effect of rpm on M, PS concentration, and initial pH, and that of temperature on IBP degradation kinetics and the PS activation mechanism. The resulting IBP oxidation rate constant was significantly higher at 400 rpm. As the PS load increased, the IBP oxidation rate constant increased. The value of the IBP reaction rate increased with decreasing pH; below pH 4.9, there was no significant difference in the IBP oxidation rate constant. The IBP oxidation activation energy when using the US/M-PS system was 18.84 kJ mol^-1. In the US/M-PS system, PS activation was the primary effect of temperature at the interface during the explosion of cavitation bubbles. These encouraging results suggest that the US-PS/M process is a promising strategy for the treatment of IBP-based water pollutants.

Influence of the Catalyst Particle Size on the Aqueous Phase Reforming of n-Butanol Over Rh/ZrO2

Butanol is a by-product obtained from biomass that can be valorized through aqueous phase reforming. Rh/ZrO₂ catalysts were prepared and characterized, varying the size of the support particles. The results showed a relatively mild effect of internal mass transport on butanol conversion. However, the influence of internal transport limitations on the product distribution was much stronger, promoting consecutive reactions, i.e., dehydrogenation, hydrogenolysis, and reforming of propane and ethane. Hydrogen consuming reactions, i.e., hydrogenolysis, were more strongly enhanced than hydrogen producing reactions due to internal concentration gradients. Large support particles deactivated faster, attributed to high concentrations of butyraldehyde inside the catalyst particles, enhancing deposit formation via aldol condensation reactions. Consequently, also the local butyric acid concentration was high, decreasing the local pH, enhancing Rh leaching. The influence of internal transfer limitation on product distribution and stability is discussed based on a reaction scheme with three main stages, i.e., (1) formation of liquid intermediates via dehydrogenation, (2) formation of gas via decarbonylation/decarboxylation reactions, and (3) hydrocarbon hydrogenolysis/reforming/dehydrogenation.