Acetohydroxamic acid adsorbed at copper surface: electrochemical, Raman and theoretical observations

Nitrite anodic oxidation at Ni(II)/Ni(III)-decorated mesoporous SnO2 and its analytical applications

Hydrothermally formed mesoporous SnO2 was used as a support for nickel chemical deposition and, after subsequent thermal treatment, a high specific surface area (36 m2 g-1) Ni/SnO2 material was obtained. XPS analysis has shown that in the Sn 3d region the spectrum is similar to that of pristine SnO2, whereas Ni species are present on the surface as NiO, Ni2O3 and Ni(OH)2. Mixing Ni/SnO2 with a small amount of Black Pearls (BP) leads to a significant enhancement of the resulting Ni/SnO2-BP composite activity for nitrite anodic oxidation, presumably due to the higher surface area (115 m2 g-1), to better electrical conductivity and to a certain contribution of the BP to an increase in surface density of the active sites. Ni/SnO2-BP also outperforms pristine BP (in terms of Tafel slopes and electron-transfer rates), most likely due to the fact that the Ni(II)/Ni(III) couple can act as an electrocatalyst for nitrite oxidation. A voltammetric method is proposed for the determination of nitrite, over a concentration range of three orders of magnitude (0.05 to 20 mM), with good reproducibility, high stability and excellent sensitivity. The high upper limit of the dynamic range of the analytically useful response might provide a basis for the reliable quantification of nitrite in wastewater.

Optimizing RuOx-TiO2 composite anodes for enhanced durability in electrochemical water treatments

Metal oxide anode electrocatalysts are important for an effective removal of contaminants and the enhancement of electrode durability in the electrochemical oxidation process. Herein, we report the enhanced lifetime of RuO_x-TiO₂ composite anodes that was achieved by optimizing the fabrication conditions (e.g., the Ru mole fraction, total metal content, and calcination time). The electrode durability was assessed through accelerated service lifetime tests conducted under harsh environmental conditions, by using 3.4% NaCl and 1.0 A/cm². The electrochemical characteristics of the anodes prepared with metal oxides having different compositions were evaluated using cyclic voltammetry, electrochemical impedance spectroscopy, and X-ray analyses. We noticed that, the larger the Ru mole fraction, the more durable were the electrodes. The RuO_x-TiO₂ electrodes were found to be highly stable when the Ru mole fraction was >0.7. The 0.8RuO_x-0.2TiO₂ electrode was selected as the one with the most appropriate composition, considering both its stability and contaminant treatability. The electrodes that underwent a 7-h calcination (between 1 and 10 h) showed the longest lifetime under the tested conditions, because of the formation of a stable Ru oxide structure (i.e., RuO₃) and a lower resistance to charge transfer. The electrode deactivation mechanism that occurred due to the dissolution of active catalysts over time was evidenced by an impedance analysis of the electrode itself and surface elemental mapping.

Active site-dominated electromagnetic enhancement of surface-enhanced Raman spectroscopy (SERS) on a Cu triangle plate

Revealing the sensitivity and selectivity of the Raman enhancement mechanism is extremely significant for disease diagnosis, environmental surveillance, and food safety supervision. In this study, chemical erosion copper triangle plates (CTPs) were employed as SERS substrate to detect the rhodamine B (Rh B) probe molecule at different etching times. A simple and cost-effective method affords unique insights into the surface enrichment of analytes, which could facilitate the high-performance SERS analysis of numerous analytes. The relationship between the Raman intensity and the concentration of Rh B follows the Freundlich model, which means that the wet-etching surface can create SERS-active site attachment Rh B molecules on the CTPs. The morphology of CTPs was modified by H₂O₂/HCl etchants; however, the composition of CTPs remained stable without oxidation. This proposes that the largest contribution to the enhancement was the hot-spots that can produce surface plasma resonance on the CTPs. The number of hot-spots can be intelligently adjusted by the artificial control of the surface morphology of metal materials, providing an unambiguous improvement in the SERS sensitivity and capability.

Chemical etching CTP to create a rough surface that has high enhancement factors of SERS.

Nano- to Micro-Self-Aggregates of New Bisimidazole-Based Copoly(ionic liquid)s for Protecting Copper in Aqueous Sulfuric Acid Solution

This study presents the synthesis of two new bisimidazole-based copoly(ionic liquid)s (PILs) through multistep preparation routes. It is shown that the target PILs can display orderly molecular stacking, and nano- to micro-self-aggregates are yielded in aqueous sulfuric acid solution, which are characterized by various technologies including scanning electron microscopy, transmission electron microscopy, and dynamic light scattering. The studied PIL aggregates show strong chemical adsorption onto the copper surfaces demonstrated by Fourier transform infrared spectroscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy. Furthermore, the anticorrosion performance of the studied PIL aggregates is shown using polarization curves and impedance spectroscopy. As a result, the target PIL aggregates show great corrosion inhibition performance to protect copper in aggressive acid medium.