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The oxygen reduction reaction (ORR) is the key operating process that determines the efficiency of energy storage and conversion devices; however, due to sluggish kinetics, it requires a catalyst. ...

Electrochemical oxygen reduction in aprotic media is a key process that determines the operation of advanced metal–oxygen power sources, e.g., Li–O2 batteries. In such systems oxygen reduction on carbon-based positive electrodes proceeds through a complicated mechanism that comprises several chemical and electrochemical steps involving either dissolved or adsorbed species, and as well side reactions with carbon itself. Here, cyclic voltammetry was used to reveal the effects of imperfections in the planar sp2 surface structure of carbon on the Li oxygen reduction reaction (Li-ORR) mechanism by means of different model carbon electrodes (highly oriented pyrolytic graphite (HOPG), glassy carbon, basal, and edge planes of pyrolytic graphite), in dimethyl sulfoxide (DMSO)-based electrolyte. We show that the first electron transfer step O2 + e– ⇆ O2– (followed by ion-coupling Li+ + O2– ⇆ LiO2) does not involve oxygen chemisorption on carbon as evidenced by the independence of its rate on the carbon electrode su...

Quasi-free-standing one-dimensional (1D) SnTe crystals were grown within the channels of single-walled carbon nanotubes (SWCNTs) from the melt using the capillary technique. The crystal structure o...

The adsorption of molecular oxygen on PbTe(001) surfaces has been investigated using synchrotron radiation induced photoelectron spectroscopy (BESSY II, Berlin). The behavior of adsorbate system O2/PbTe(001) was also modeled in complementary DFT-B3LYP studies using a large-cluster approach. For several possible adsorption structures, the adsorption enthalpies, the changes of the effective charges, and the core-level shifts induced by adsorption were calculated. For the energetically most favorable adsorption structures, the calculated chemical shifts are in good agreement with the experimental observations. Oxidation was observed at exposures above ∼105 L of O2. In total, three steps of oxidation were observed. The first step of the reaction is associated with the formation of Te−O−Pb bonds resulting in Te0 states. The subsequent second step is characterized by a Te0→Te4+ transformation with three O atoms attaching to each surface Te atom. As a result, −TeO32− species are formed. The third step is associa...

The interaction of the semiconductor compounds PbS, PbSe, and PbTe with H 2 S was studied using X-ray photoemission spectroscopy performed at the synchrotron radiation facility BESSY II. For all surfaces sulfidation subsequent to dissociation of H 2 S was observed. For PbS, the sulfur atoms occupy the surface anion vacancies. In the case of PbSe, either a similar interaction or an anion substitution at the surface takes place; besides, H 2 S adsorption leads to the agglomeration of additional sulfur atoms forming S n 2- . For the reaction of H 2 S with PbTe surfaces we suggest a mechanism which includes at least three steps. The first step leads to a formation of Pb-S-Te bonds, which is also supported by the results of quantum chemical calculations performed in the framework of cluster approach. The subsequent steps include further gradual oxidation of the tellurium atoms and result finally in the formation of quite stable thiotellurite species.