Electrochimica Acta最新文献

Owing to the presence of valence shells for charge transfer, a high theoretical specific capacitance, and variable redox properties, MnO₂ appears as a promising agent in the realm of energy storage. Crystallographic structures of manganese oxide (MnO₂), a transition metal oxide, play a crucial role in determining its capacitive behavior by controlling the ion intercalation and double-layer formation. In this work, two different phases of MnO₂ were synthesized using the facile chemical reduction method and biological method, say α-MnO₂ and λ-MnO₂. The phases were incorporated with different carbonaceous additives including GO and CNT while maintaining a constant weight ratio of 8:1:1 between active materials (MnO₂), additive, and PVDF binder. Among different composites formed, the best electrode performance is demonstrated by λ-MnO₂/CNT/PVDF composite with an excellent specific capacitance of 356 F/g at a scan rate of 1 A/g. Moreover, the best-performing electrodes are investigated with a symmetrical two-electrode system yielding a wide potential window of 1.8V with an outstanding power density of 13.5 KW/Kg at 5 A/g and an energy density of 53.78 Wh/Kg at 1A/g having a specific capacitance of 190 F/g.

The measurements of gas volumes evolved during electrochemical wastewater treatment provide the information on the process faradaic efficiency. This work demonstrates how it enables identification of the water oxidation pathway (2 or 4 electron) in flow electrolysis process through the application of the formulae suggested in the study. This way, the real wastewater oxidation strength, i.e. production of hydrogen peroxide can be determined based on calculations. These provide more accurate results than direct measurements of accumulated hydrogen peroxide concentration after the electrolysis process, as its instability may lead to its immediate decomposition and false results. As an example provided in the paper, the application of MoO₃ as a catalyst in the carbon composite electrode indicates almost no hydrogen peroxide detected after the process, whereas its oxidative properties owing to production of hydroxyradicals demonstrate complete decomposition of wastewater analogue (methylene blue). The calculations point to high production of H₂O₂. Using pure carbon material without the catalyst in the same experiment, decomposition occurs at much lower rate. The possible mechanisms behind the processes are discussed. The approach presented in the work can aid to efficient development of catalysts towards two-electron water oxidation.

Electrochemical water splitting is a zero-carbon-emission and environmentally friendly method for hydrogen production. However, the process requires electrocatalysts to lower its energy requirements. In this study, Si-doped cobalt–aluminum layered double hydroxide (Si-CoAl-LDH) had been successfully synthesized by SiCl₄ chemical etching at room temperature. The Co-O-Si chemical bonds promoted the formation of γ-CoOOH_x during the process of water oxidation, thereby increasing the number of active sites. Moreover, Theoretical calculations revealed the overlap of atomic orbitals on the Si-CoAl-LDH catalyst surface and the improved electronic structure due to Co–O–Si chemical bonds. The Si-CoAl-LDH exhibited overpotentials of 295, 336, and 363 mV for oxygen evolution reactions (OERs) at current densities 10, 50, and 100 mA cm⁻², respectively. The Tafel slope of the sample was 74.16 mV·dec⁻¹. Physical characterization and in situ Raman analysis revealed the formation of intermediate hydroxylated cobalt species, which act as active centers during OER. This study serves as a basis for the surface reconstruction and activity enhancement of other electrocatalysts through Si doping.