New Scale Insects (Homoptera: Coccoidea) in the Greek Entomofauna

Η γνώση της πανίδας των κοκκοειδών εντόμων της Ελλάδος είναι περιορισμένη. Για το λόγο αυτό έγινε προσπάθεια συλλογής και αναγνώρισης τέτοιων εντόμων κατά τη διετία 1990-91.  Κατά τη συλλογή αυτή συλλέχΟησαν 71 είδη, που ανήκουν σε οκτώ οικογένειες, συγκεκριμένα στις Ortheziidae, Margarodidac, Pseudococcidae, Eriococcidae, Kermesidae, Cerococcidae, Coccidae και Diaspididae. Τα 31 ήταν νέα για την ελληνική πανίδα. Καταγράφηκαν επίσης το επίπεδο προσβολής, τα φυτά ξενιστές, καθώς επίσης και φαινολογικά δεδομένα. Τα αποτελέσματα δείχνουν ότι η πανίδα των κοκκοειδών εντόμων στη χώρα μας χρειάζεται επιπλέον μελέτη.Collection of scale insects in Greece in 1990 – 1991 provided 71 species. Among them, 31 species were new for the Greek fauna. The total number of known species is 143 in Greece. Host plant’s levels of infestation and phonological data are also presented. The results show that scale insect fauna of this country needs further intensive studies

Is Steam an Oxidant or a Reductant for Nickel Doped Ceria Cermets?

Nickel/doped‐ceria composites are promising electrocatalysts for solid‐oxide fuel and electrolysis cells. Very often steam is present in the feedstock of the cells, frequently mixed with other gases, such as hydrogen or CO(2). An increase in the steam concentration in the feed mixture is considered accountable for the electrode oxidation and the deactivation of the device. However, direct experimental evidence of the steam interaction with nickel/doped‐ceria composites, with adequate surface specificity, are lacking. Herein we explore in situ the surface state of nickel/gadolinium‐doped ceria (NiGDC) under O(2), H(2), and H(2)O environments by using near‐ambient‐pressure X‐ray photoelectron and absorption spectroscopies. Changes in the surface oxidation state and composition of NiGDC in response to the ambient gas are observed. It is revealed that, in the mbar pressure regime and at intermediate temperature conditions (500–700 °C), steam acts as an oxidant for nickel but has a dual oxidant/reductant function for doped ceria

Operando observation of nickel ceria electrode surfaces during intermediate temperature steam electrolysis

The solid oxide electrolysis cell (SOEC) technology has a huge potential for future mass production of hydrogen, mainly due to its high electrical-to-chemical energy conversion efficiency. However, the durability and the performance of SOEC devices are inferior to that of other competitive electrolysis technologies inhibiting the commercialization of SOECs. Despite the fact that Ni-based cermets are currently the most widely used cathode materials for SOEC, change of the nickel oxidation state has been accused as a major issue limiting the performance of these devices. In this work we provide operando experimental evidence of the active surface oxidation state and composition of nickel/doped-ceria cermets under water electrolysis conditions using ambient pressure X-ray photoelectron and near edge X-ray absorption fine structure spectroscopies, combined with quantitative spectra simulation. Remarkably under specific operational conditions, nickel is maintained in a partially oxidized state which, counterintuitive to the expected behavior, can be beneficial to the cell performance. This finding may initiate new improvement strategies for SOEC electrodes based on thorough optimization of the operational conditions, in order to engineer in situ the most propitious electrode configuration

A comparative in situ XPS study of PtRuCo catalyst in methanol steam reforming and water gas shift reactions

In the present study the oxidation state and the surface composition of a ternary PtRuCo catalyst were investigated under methanol steam reforming (SRM) and water gas shift (WGS) reaction conditions at 570 K. Ambient pressure X-ray photoelectron spectroscopy (APPES) was applied in situ at 0.5 mbar, while simultaneously monitoring the catalytic activity of the sample by on-line mass spectrometry. Non-destructive depth profile measurements performed under SRM reaction conditions over a polycrystalline PtCo foil, were also used to obtain detailed depth-resolved information. The results showed that surface segregation of cobalt and modification of its oxidation state occurs when switching from SRM to WGS reaction conditions. Evidence of ionic Pt was found only during WGS reaction, while Ru was mainly present in the metallic state. The results clearly demonstrate the dynamic response of the PtRuCo catalytic surface to the reaction atmosphere

Revising the role of chromium on the surface of perovskite electrodes Poison or promoter for the solid oxide electrolysis cell performance?

Perovskite materials are typically used as oxygen electrodes of solid oxide fuel and electrolysis cells (SOC). The high stability of the perovskite structure in oxidative environments makes it a good candidate as a cathode electrode for steam electrolysis SOC as well. In this work, we investigate SOC with La0.75Sr0.25Cr0.9Fe0.1O3 perovskite cathodes employing near ambient pressure X-ray photoelectron and near-edge X-ray absorption fine structure spectroscopies combined with online electrochemical measurements. Based on operando experimental evidences the surface state of the perovskite electrode is directly associated with the electrocatalytic performance of the cell. The results indicate that under steam electrolysis operating conditions the well-known Sr surface enrichment is accompanied by Cr segregation and formation of SrCrO4-like oxide. In contrast to the common perception of the role of surface chromites, we show here that its presence does not induce cell deactivation, but on the contrary, is beneficial for cell performance. (C) 2019 Elsevier Inc. All rights reserved

Influence of surface state on the electrochemical performance of nickel-based cermet electrodes during steam electrolysis

International audienceDue to their fuel flexibility and high efficiency, solid oxide cells are apromising technology for sustainable energy production and storage. Nickel incombination with yttria-stabilized zirconia (YSZ) or gadolinium-doped ceria (GDC),forming Ni-YSZ or Ni-GDC cermets respectively, are the most widely adoptedelectrodes in solid oxide fuel cell fabrication. Currently, there is an increasing interestin cermet electrodes for hydrogen generation through high temperature steamelectrolysis using solid oxide electrolysis cells (SOECs). However, durability remainsa major issue for reliable operation of SOEC systems. A variety of processesaccountable for permanent performance degradation of SOECs has been identifiedbased on post-mortem cell analysis. Besides, transient/reversible degradationprocesses are typically examined by indirect methods, like impedance spectroscopy.The reason is that the application of material characterization techniques duringSOEC operational conditions is challenging. In this work we provide a directcorrelation between Ni-YSZ and Ni-GDC electrode surface oxidation states and their performance during steam electrolysisusing operando experimental evidence provided by near ambient pressure X-ray photoelectron and near edge X-ray absorptionfine structure spectroscopy. We show that nickel surface oxidation may induce significant performance degradation in Ni-YSZcathodes while, on the contrary, having minor effects in Ni-GDC. Remarkably, we found that in the case of Ni-GDC electrodes,small modification of the GDC oxidation state can have an important impact on the electrolysis performance. The resultshighlight the crucial role of the cathode electrode surface oxidation state on the SOEC functionality and have potentialimplications for the design and operation strategies of more efficient and durable SOEC devices