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 similar 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 go 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

Time‐ and potential‐resolved electrochemical Pt dissolution from commercial Pt and prepared PtCu alloy nanoparticulate catalysts have been studied under potentiodynamic conditions in 0.1 M HClO4 by using on‐line inductively coupled plasma mass spectrometry (ICP‐MS). For the first time the exact amount of dissolved Pt per cycle has been measured on real electrocatalysts. Results show clearly that Pt dissolution depends on the particle size: approximately seven times as much Pt is released into the solution from commercial 3 nm Pt particles as from a commercial 30 nm Pt sample. The stability of our prepared PtCu electrocatalyst is higher than that of a commercial 3 nm electrocatalyst, which is, however, still slightly lower than that of a commercial 30 nm Pt electrocatalyst.

Corrosion resistance of a transition-metal-rich PtCu3/C oxygen reduction reaction (ORR) catalyst as a representative of Pt alloy-based materials has been significantly improved by doping with small amounts of gold (<1 at. %). Transmission electron microscopy imaging shows near-surface segregation of both platinum and gold with the underlying core consisting predominantly of intermetallic PtCu3. The resulting PtAu skin catalyst shows improved resistance against Cu dissolution, as well as against carbon corrosion if compared to its PtCu3 precursor. Also, it exhibits a much higher Pt and carbon stability than a widely used Pt/C standard. Most importantly, the Au doped sample shows a substantial improvement in stability at the elevated temperature (60 degrees C) degradation test (10 000 cycles; 0.4-1.2 Vim) simulating a real PEM fuel cell environment

Summary Achieving highly active and stable oxygen reduction reaction performance at low platinum-group-metal loadings remains one of the grand challenges in the proton-exchange membrane fuel cells community. Currently, state-of-the-art electrocatalysts are high-surface-area-carbon-supported nanoalloys of platinum with different transition metals (Cu, Ni, Fe, and Co). Despite years of focused research, the established structure-property relationships are not able to explain and predict the electrochemical performance and behavior of the real nanoparticulate systems. In the first part of this work, we reveal the complexity of commercially available platinum-based electrocatalysts and their electrochemical behavior. In the second part, we introduce a bottom-up approach where atomically resolved properties, structural changes, and strain analysis are recorded as well as analyzed on an individual nanoparticle before and after electrochemical conditions (e.g. high current density). Our methodology offers a new level of understanding of structure-stability relationships of practically viable nanoparticulate systems.

Despite the fact that the methanol synthesis process includes industrially some of the most important catalytic chemical reactions, it is still not clear how different gaseous species impact catalyst component structure. With the goal to reduce CO2 emissions through hydrogenation to CH3OH, a higher H2O formation rate than in the production from compressed CO-rich feed should also be considered. It is known that steam accelerates the sintering of metals, several oxide compounds, and their interfaces. To determine the effect of moisture on the Cu/ZnO/Al2O3 catalysts, a commercial catalytic material was systematically aged at various gas compositions and analyzed using transient H2 surface adsorption, N2O pulse efficient chemisorption, X-ray photoelectron spectroscopy, scanning transmission electron microscopy mapping, X-ray powder diffraction, and N2 physisorption, and the mechanisms of deactivation were observed. A strong consistent relation between the compacting of Al2O3, the amount of water in the controlled streamflow, and the activity was found. This connected loss of support resulted in the (re)­forming of Cu, ZnO, and Cu/ZnO phases. Copper particle growth was modeled by applying a physical coalescence model. In the presence of CO and/or CH3OH, zinc oxide material started to cover the Cu granules, while H2O promoted the development of separate Cu regions.

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.

Potentiodynamic Pt/C fuel cell catalyst corrosion has been studied as a function of chloride concentration with an electrochemical flow cell (EFC) coupled with highly sensitive ICP-MS. The Pt corrosion mechanism changes significantly: the anodic corrosion is much enhanced compared to the cathodic corrosion that prevails in electrolytes without Cl(-).

We present a novel, scaled-up sol-gel synthesis which enables one to produce 20 g batches of highly active and stable carbon supported PtCu3 nanoparticles as cathode materials for low temperature fuel cell application. We confirm the presence of an ordered intermetallic phase underneath a multilayered Pt-skin together with firm embedment of nanoparticles in the carbon matrix.