Online Monitoring of Methanol Electro-Oxidation Reactions by Ambient Mass Spectrometry

CaCu3Ti4O12 Perovskite Materials for Advanced Oxidation Processes for Water Treatment

The many pollutants detected in water represent a global environmental issue. Emerging and persistent organic pollutants are particularly difficult to remove using traditional treatment methods. Electro-oxidation and sulfate-radical-based advanced oxidation processes are innovative removal methods for these contaminants. These approaches rely on the generation of hydroxyl and sulfate radicals during electro-oxidation and sulfate activation, respectively. In addition, hybrid activation, in which these methods are combined, is interesting because of the synergistic effect of hydroxyl and sulfate radicals. Hybrid activation effectiveness in pollutant removal can be influenced by various factors, particularly the materials used for the anode. This review focuses on various organic pollutants. However, it focuses more on pharmaceutical pollutants, particularly paracetamol, as this is the most frequently detected emerging pollutant. It then discusses electro-oxidation, photocatalysis and sulfate radicals, highlighting their unique advantages and their performance for water treatment. It focuses on perovskite oxides as an anode material, with a particular interest in calcium copper titanate (CCTO), due to its unique properties. The review describes different CCTO synthesis techniques, modifications, and applications for water remediation.

Recent Advances of In-Source Electrochemical Mass Spectrometry

Hyphenation of electrochemistry (EC) and mass spectrometry has become a powerful tool to study redox processes. Approaches that can achieve this hyphenation include integrating chromatography/electrophoresis between electroinduced redox reactions and detection of products, coupling an EC flow cell to a mass spectrometer, and performing electrochemical reactions inside the ion source of a mass spectrometer. The first two approaches have been well reviewed elsewhere. This Minireview highlights the inherent electrochemical properties of many mass spectrometry ion sources and their roles in the coupling of electrochemistry and mass spectrometric analysis. Development of modified ion sources that allow the compatibility of electrochemistry with ionization processes is also surveyed. Applications of different in-source electrochemical devices are provided including intermediate capturing, bioanalytical studies, nanoparticle formation, electrosynthesis, and electrode imaging.

Metal-Based Electrocatalysts for Methanol Electro-Oxidation: Progress, Opportunities, and Challenges

Direct methanol fuel cells (DMFCs) are among the most promising portable power supplies because of their unique advantages, including high energy density/mobility of liquid fuels, low working temperature, and low emission of pollutants. Various metal-based anode catalysts have been extensively studied and utilized for the essential methanol oxidation reaction (MOR) due to their superior electrocatalytic performance. At present, especially with the rapid advance of nanotechnology, enormous efforts have been exerted to further enhance the catalytic performance and minimize the use of precious metals. Constructing multicomponent metal-based nanocatalysts with precisely designed structures can achieve this goal by providing highly tunable compositional and structural characteristics, which is promising for the modification and optimization of their related electrochemical properties. The recent advances of metal-based electrocatalytic materials with rationally designed nanostructures and chemistries for MOR in DMFCs are highlighted and summarized herein. The effects of the well-defined nanoarchitectures on the improved electrochemical properties of the catalysts are illustrated. Finally, conclusive perspectives are provided on the opportunities and challenges for further refining the nanostructure of metal-based catalysts and improving electrocatalytic performance, as well as the commercial viability.

Mass Spectrometry-Based Discovery of New Chemical Scaffold Rearrangement Ions: Aza-biphenylene as a Novel Potent Biradical Agent in Cancer Chemotherapy

Discovery of a new drug is time-consuming, laborious, and expensive. Herein, a novel integrative strategy for discovering potential new lead compounds has been developed, which was based on the characteristics of mass spectrometry (MS). MS was used to predict the potential forced degradation products (DPs) and metabolites of drugs by electrospray ionization and collision-induced dissociation (CID). Special rearrangement ions representing unique predicted DPs and metabolites were identified. The consistency between the predicted and the measured results was proven by in vitro metabolism and forced degradation of a commercial drug, respectively. From this, new chemical scaffold rearrangement ions named (aza)-biphenylenes, as potent anticancer agents, were discovered. As a representative aza-biphenylene analogue, 2-azabiphenylene was proven in vitro to induce apoptosis and inhibit the growth of various human cancer cells in a dose-dependent manner. Surprisingly, 2-azabiphenylene exhibited the best comparable bioactivity with the positive control sorafenib, but showed significantly lower in vitro cytotoxicity than sorafenib (at least a 5-fold decrease in cytotoxicity) because it could be targeted to the tumor microenvironment at low pH. A biradical mechanism accompanied by a mitochondrion-dependent oxidative stress mechanism was proposed to explore its anticancer mechanism. The highly reactive intermediate aza-biphenylenediyl worked as an active pharmaceutical ingredient and induced apoptosis of cancer cells. This provided the basis for the potential applications of CID-induced special rearrangement ions in developing new lead compounds.

In operando imaging of self-catalyzed formaldehyde burst in methanol oxidation reactions under open circuit conditions

A wave-like HCHO burst is in situ observed during electro-oxidation of methanol on Pt under open circuit conditions by SPR imaging.

We employ a surface plasmon resonance imaging (SPRi) technique to monitor the in operando process of formaldehyde (HCHO) production during methanol oxidation with high spatial and temporal resolutions. While common wisdom suggests HCHO is generated as an intermediate during continuous electron transfer towards CO₂, we find that the majority of HCHO is produced via self-catalyzed chemical and electrochemical reactions under open-circuit conditions, which lead to an unprecedented HCHO burst immediately after withdrawal of external potential. Because open-circuit conditions better represent the operating environments of practical direct methanol fuel cells (DMFCs), this work uncovers a hidden pathway of HCHO accumulation by adopting a quantitative and in operando SPRi technique for the first time. These theoretical and technical advances are anticipated to help the fundamental understanding of the comprehensive mechanism of methanol oxidation with implications for improving the performance of DMFCs.