Iridium-based particles, regarded as the most promising proton exchange membrane electrolyzer electrocatalysts, were investigated by transmission electron microscopy and by coupling of an ...electrochemical flow cell (EFC) with online inductively coupled plasma mass spectrometry. Additionally, studies using a thin-film rotating disc electrode, identical location transmission and scanning electron microscopy, as well as X-ray absorption spectroscopy have been performed. Extremely sensitive online time-and potential-resolved electrochemical dissolution profiles revealed that Ir particles dissolve well below oxygen evolution reaction (OER) potentials, presumably induced by Ir surface oxidation and reduction processes, also referred to as transient dissolution. Overall, thermally prepared rutile-type IrO2 particles are substantially more stable and less active in comparison to as-prepared metallic and electrochemically pretreated (E-Ir) analogues. Interestingly, under OER-relevant conditions, E-Ir particles exhibit superior stability and activity owing to the altered corrosion mechanism, where the formation of unstable Ir(>IV) species is hindered. Due to the enhanced and lasting OER performance, electrochemically pre-oxidized E-Ir particles may be considered as the electrocatalyst of choice for an improved low-temperature electrochemical hydrogen production device, namely a proton exchange membrane electrolyzer.
Laser ablation (LA) in combination with inductively coupled plasma mass spectrometry (ICP-MS) is a technically advanced micro-analytical method for direct sampling of solid materials and allows the ...determination of a majority of elements from the periodic table. In recent years, the technology has undergone major improvements in hardware, software and the methodology, which have led to a significant reduction of the analysis time, higher spatial resolution/image quality, better sensitivity and signal to noise ratios. Reliable and validated quantification procedures remain one of the bottlenecks in LA-ICPMS bioimaging. This review provides a comprehensive overview on different quantification strategies commonly used for bioimaging applications by LA-ICPMS. The advantages and drawbacks of existing quantification approaches in terms of analytical capabilities will be critically discussed and showcases of their application to biological samples will be presented. Recent developments and future perspectives of the field will be discussed.
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•Overview of different quantification strategies commonly used for bioimaging applications by LA-ICPMS.•Calibration strategies for bioimaging by LA-ICPMS are based on matrix-matched standards.•Nanoparticle analysis and immuno-mass spectrometry imaging are emerging fields.•Presentation of showcases for the application of quantification for biological samples.
Extremely sensitive on-line detection of metal ions concentration was used to investigate potential-resolved platinum dissolution from commercial fuel cell electrocatalyst. The experiments were ...carried out in an electrochemical flow cell connected to inductively coupled plasma mass spectrometer. A variety of electrochemical treatments using different voltage scan rates confirmed the previously observed primary platinum degradation mechanism - the so-called "transient dissolution". Importantly, the redeposition of dissolved platinum is now shown to play an important role in the overall effective Pt dissolution. Pt redeposition trends exhibit a significant dependence on voltage scan rate.
Palladium has attracted significant attention as a catalyst or co-catalyst for many electrochemical reactions in energy conversion devices. We have studied electrochemical stability of a commercial ...Pd/C sample in an acidic electrolyte by exposing it to an accelerated stress test (AST) to mimic potential spikes in fuel cells and electrolyzers during start/stop events. AST consisted of extensive rapid potential cycling (5000 cycles, 1 V/s) in two potential regions, namely AST1 was performed between 0.4 and 1.4 VRHE, while AST2 was performed between 0.05 and 1.4 VRHE. Degradation of Pd/C was monitored by the changes in Pd electrochemical surface area, while the hydrogen evolution reaction (HER) was used as a test reaction to observe the corresponding impact of the degradation on the activity of Pd/C. Significant Pd/C degradation and HER activity loss were observed in both potential regions. Coupling of the electrochemical flow cell with an inductively coupled plasma mass spectrometry device showed substantial Pd dissolution during both ASTs. Identical location scanning electron microscopy revealed that Pd dissolution is followed by redeposition during both ASTs, resulting in particle size growth. Particle size growth was seen as especially dramatic in the case of AST2, when particularly large Pd nanostructures were obtained on top of the catalyst layer. According to the results presented in this work, (in)stability of Pd/C and other Pd-based nanocatalysts should be studied systematically as it may present a key factor limiting their application in energy conversion devices.
Phenols are hazardous, but yet ubiquitous in the environment, including in atmospheric aerosols due to combustion emissions. There, phenols are subjected to secondary transformations, producing even ...more toxic nitrophenolic air pollutants. However, primary simple phenols, i.e. those containing only hydroxyl, methyl and methoxy substituents are not easy to detect. Trace concentrations, semi-volatile character and poorly ionizable functional groups prevent us from their determination by the most common analytical techniques, such as gas and liquid chromatography with mass spectrometric detection (GC/LC-MS). Here, we present a new derivatization method for MS/MS detection with positive ion electrospray ionization (+ESI-MS/MS) of simple phenols in atmospheric particulate matter (PM) extracts. The method is sensitive, selective, and robust, and requires no sample concentration step, which is critical due to the volatile character of the target analytes. After derivatization with dansyl chloride, phenol, catechol, cresols and guaiacol were detected in urban PM samples from Ljubljana, Slovenia. This method finally enables to study the abundance of primary phenols in atmospheric PM from different sources, which will improve understanding of secondary aerosol (trans)formation pathways and allow for more targeted mitigation strategies in respect to airborne phenolic pollutants.
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•Phenol dansylation improves ionization and enables LC-MS analysis.•Optimal reaction and measuring parameters provide very low limits of detection.•Phenol, catechol, guaiacol and cresol are determined in ambient particulate matter.•Concentrations of simple phenols in particulate matter are low, peaking in winter.•Simple phenols can be precursors to toxic secondary aerosols (e.g. nitrophenols).
This work presents the novel and entirely green in situ synthesis of zinc oxide nanoparticles (ZnO-NP) on cotton fabric. Pomegranate peel extract was used as a reducing agent and wood ash extract was ...used as an alkali source for the formation of ZnO-NP from zinc acetate. Four different synthesis methods, which varied in drying between immersion of fabric in the active solutions for synthesis and the use of padding and ultrasonication, were investigated to evaluate the most suitable one to achieve excellent ultraviolet (UV) protective properties of the functionalized textile. For comparison, the cotton fabrics were also functionalized with each active solution separately or in a combination of two (i.e., Zn-acetate and plant extract). Scanning electron microscopy (SEM), inductively coupled plasma mass spectroscopy (ICP-MS), Fourier transform infrared spectroscopy (FTIR), X-ray diffractometry (XRD) analysis, and atomic force microscopy (AFM) confirm the successful formation of ZnO-NP on cotton. Among the synthesis methods, the method that included continuous drying of the samples between immersion in the active solutions for synthesis (Method 4) was found to be the most suitable to deliver uniformly impregnated cotton fibers with numerous small ZnO wurtzite structured crystals and excellent UV protection, with a UV protection factor of 154.0. This research presents an example of a green circular economy where a bio-waste material can be used to produce ZnO-NP directly on cotton at low temperatures and short treatment times without the addition of chemicals and enables the production of cellulosic fabrics with excellent UV protection.
The dissolution behaviors of Ru and ruthenium oxide nanoparticles in acidic media were studied for the first time using highly sensitive in situ measurements of concentration by inductively coupled ...plasma mass spectrometry (ICP-MS). Online time- and potential-resolved electrochemical dissolution profiles revealed novel corrosion features (signals) in the potential window from 0 to ∼1.4 V, where known severe dissolution due to the oxygen evolution reaction (OER) takes place. Most of the features follow the thermodynamic changes of the Ru oxidation/reduction state, which consequently trigger so-called transient dissolution. An as-synthesized Ru sample was found to exhibit an order-of-magnitude higher dissolution rate than an electrochemically oxidized amorphous Ru sample. The latter, in turn, dissolved about 10 times faster than rutile RuO2. The observed OER activity was in an inverse relationship with the measured dissolution. Disagreement was found with the general assumption that the onset of the OER should coincide with the onset of Ru dissolution. Interestingly, in all samples, Ru dissolution was observed at about 0.17 V lower potentials than the OER. The present results are relevant for various energy-conversion and -storage devices such as proton-exchange membrane electrolyzers, low-temperature fuel cells, reverse fuel cells, supercapacitors, batteries, and photocatalysts that can contain Ru as an active component.
This study aims to investigate the potential benefits of adapting the ablating grid in two-dimensional (2D) and three-dimensional (3D) laser ablation inductively coupled plasma mass spectrometry in a ...single pulse mapping mode. The goals include enhancing the accuracy of surface sampling of element distributions, improving the control of depth-related sampling, smoothing the post-ablation surface for layer-by-layer sampling, and increasing the image quality. To emulate the capabilities of currently unavailable laser ablation stages, a computational approach using geometrical modeling was employed to compound square or round experimentally obtained 3D crater profiles on variable orthogonal or hexagonal ablation grids. These grids were optimized by minimizing surface roughness as a function of average ablation depth, followed by simulating the post-ablation surface and related image quality. An online application (https://laicpms-apps.ki.si/webapps/home/) is available for users to virtually experiment with contracting/expanding orthogonal and hexagonal ablation grids for generic 3D super-Gaussian laser crater profiles, allowing for exploration of the resulting post-ablation surface layer roughness and depth.
The positive effect of intermetallic ordering of platinum alloy nanoparticles on oxygen reduction reaction (ORR) activity has been well established. What is still missing is an understanding of ...selective leaching of the less noble metal from the ordered structure and its correlation to long-term ORR performance. Using a combination of kinetic Monte Carlo simulations and advanced characterization techniques, we provide unprecedented insight into dealloying of intermetallic PtCu3 nanoparticlesa well-known binary alloy. Comparison of ordered and disordered samples with identical initial compositions and particle size distributions reveals an unexpected correlation: whereas the copper dealloying rates in the ordered and disordered counterparts are almost the same, in the ordered structure Pt atoms are surrounded by 15–30% more Cu atoms throughout all the stages of acid leaching. This more convenient Pt–Cu coordination explains the statistically significant increase of 23–37% in ORR activity of the ordered structure at all stages of alloy degradation.
Impurity records in polar ice cores have provided invaluable insights into atmospheric aerosol concentrations of the past environment. The investigation of the oldest, deepest and highly thinned ice ...core layers is one of the most pressing tasks in today's state-of-the-art ice core research. This calls for impurity analysis at high spatial resolution, which has to take into account post-depositional processes through the interaction of impurities with the ice matrix. To this end, the technique of laser ablation inductively-coupled plasma mass spectrometry (LA-ICP-MS) has shown great potential, which still remains to be fully exploited, however. Here we demonstrate how the application of LA-ICP-MS for imaging the impurity distribution in ice cores can be refined and strongly improved. A novel cryogenic two-volume ablation chamber is paired with a rapid aerosol transfer system in order to achieve fast washout times (34 ms). In so doing, we are able to analyze ice cores for the first time using next generation LA-ICP-MS imaging techniques. The improved LA-ICP-MS method for ice cores offers not only high scan speeds for single line profiles (around 1 mm s
−1
) but can also map the localization of impurities at high spatial resolution (35 μm), at high speed and without imaging artifacts. This promises not only new insights into the impurity distribution in glacier ice but also lays the ground for an improved understanding of the LA-ICP-MS signal obtained from ice cores. As a result, LA-ICP-MS can deliver an important contribution for retrieving future paleo-environmental records from highly thinned ice layers.
The novel combination of ice core LA-ICP-MS with improved imaging techniques reveals impurity localization without artifacts.
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