High Activity and Selectivity of M-N/C Catalysts toward Two-Electron O2 Electroreduction

Hydrogen Peroxide (H2O2) is a versatile and environmentally friendly chemical oxidant with a remarkably diverse range of applications, including fine chemical synthesis, first aid kits for disinfection, pulp and textile bleaching, wastewater treatment and others. Industrial production of H2O2 is based on the anthraquinone oxidation/reduction process, which consumes a lot of energy, requires complex and large-scale equipment, and mass extraction solvents, generating an enormous waste. There is a general demand for a more decentralised infrastructure, where energy conversion and chemical synthesis are conducted closer to the point of consumption. In this context, developing an electrochemical process to partially reduce O2 to H2O2 (O2 + 2H+/e- → H2O2) in an acidic medium would be an attractive strategy that could be carried out under ambient conditions using renewable energies. However, practical and economic electrocatalysts that exhibit high activity and selectivity for hydrogen peroxide production is to be developed. A series of M-N/C catalysts (M = Fe, Co, and Cu) were prepared in the present study. The performance (activity and selectivity) of these catalysts for the oxygen reduction reaction was investigated in the potential window of 0.2 V to 1.0 V vs. the Reversible Hydrogen Electrode (RHE). Electrochemical measurements demonstrated that the Co-N/C [c] electrocatalyst exhibits high ORR activity and exceptional selectivity for hydrogen peroxide production (92% at 0.5 V vs. RHE).

Titanium Dioxide Nanoparticles are Toxic for the Freshwater Mussel Unio ravoisieri: Evidence from a Multimarker Approach

The current work investigated the ecotoxicological effects induced by Titanium Dioxide (TiO2) nanoparticles (NPs), used at three different concentrations (C1 = 10 μg·L−1, C2 = 100 μg·L−1 and C3 = 1000 μg·L−1) in a laboratory experiment, on the freshwater mussel Unio ravoisieri. Biochemical analyses of gills and digestive glands revealed a stress-related disruption of the antioxidant system. The catalase activity and the rates of malonedialdehyde and hydrogen peroxide production were significantly higher in both organs following the exposure to TiO2 NPs and was concentration-dependent. In addition, based on the observed changes in acetylcholinesterase activity, it can be concluded that the disturbance threshold for the cholinergic system was less than 1 mg·L−1 of TiO2. Overall, the results suggest that the mussel Unio ravoisieri could be used as a sentinel species in monitoring surveys assessing the environmental impact of metallic nanoparticles in freshwater systems.

Transcriptomics of single dose and repeated carbon black and ozone inhalation co-exposure highlight progressive pulmonary mitochondrial dysfunction

Background Air pollution is a complex mixture of particles and gases, yet current regulations are based on single toxicant levels failing to consider potential interactive outcomes of co-exposures. We examined transcriptomic changes after inhalation co-exposure to a particulate and a gaseous component of air pollution and hypothesized that co-exposure would induce significantly greater impairments to mitochondrial bioenergetics. A whole-body inhalation exposure to ultrafine carbon black (CB), and ozone (O3) was performed, and the impact of single and multiple exposures was studied at relevant deposition levels. C57BL/6 mice were exposed to CB (10 mg/m3) and/or O3 (2 ppm) for 3 h (either a single exposure or four independent exposures). RNA was isolated from lungs and mRNA sequencing performed using the Illumina HiSeq. Lung pathology was evaluated by histology and immunohistochemistry. Electron transport chain (ETC) activities, electron flow, hydrogen peroxide production, and ATP content were assessed. Results Compared to individual exposure groups, co-exposure induced significantly greater neutrophils and protein levels in broncho-alveolar lavage fluid as well as a significant increase in mRNA expression of oxidative stress and inflammation related genes. Similarly, a significant increase in hydrogen peroxide production was observed after co-exposure. After single and four exposures, co-exposure revealed a greater number of differentially expressed genes (2251 and 4072, respectively). Of these genes, 1188 (single exposure) and 2061 (four exposures) were uniquely differentially expressed, with 35 mitochondrial ETC mRNA transcripts significantly impacted after four exposures. Both O3 and co-exposure treatment significantly reduced ETC maximal activity for complexes I (− 39.3% and − 36.2%, respectively) and IV (− 55.1% and − 57.1%, respectively). Only co-exposure reduced ATP Synthase activity (− 35.7%) and total ATP content (30%). Further, the ability for ATP Synthase to function is limited by reduced electron flow (− 25%) and translation of subunits, such as ATP5F1, following co-exposure. Conclusions CB and O3 co-exposure cause unique transcriptomic changes in the lungs that are characterized by functional deficits to mitochondrial bioenergetics. Alterations to ATP Synthase function and mitochondrial electron flow underly a pathological adaptation to lung injury induced by co-exposure.