Browsing by Author "Xu, XM"

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    High-performance perovskite composite electrocatalysts enabled by controllable interface engineering
    (John Wiley & Sons, Inc, 2021-06-17) Xu, XM; Pan, YL; Ge, L; Chen, YB; Mao, X; Guan, DQ; Li, MR; Zhong, YJ; Hu, ZW; Peterson, VK; Saunders, M; Chen, CT; Zhang, HJ; Ran, R; Du, AJ; Jiang, SP; Zhou, W; Shao, ZP
    Single-phase perovskite oxides that contain nonprecious metals have long been pursued as candidates for catalyzing the oxygen evolution reaction, but their catalytic activity cannot meet the requirements for practical electrochemical energy conversion technologies. Here a cation deficiency-promoted phase separation strategy to design perovskite-based composites with significantly enhanced water oxidation kinetics compared to single-phase counterparts is reported. These composites, self-assembled from perovskite precursors, comprise strongly interacting perovskite and related phases, whose structure, composition, and concentration can be accurately controlled by tailoring the stoichiometry of the precursors. The composite catalyst with optimized phase composition and concentration outperforms known perovskite oxide systems and state-of-the-art catalysts by 1–3 orders of magnitude. It is further demonstrated that the strong interfacial interaction of the composite catalysts plays a key role in promoting oxygen ionic transport to boost the lattice-oxygen participated water oxidation. These results suggest a simple and viable approach to developing high-performance, perovskite-based composite catalysts for electrochemical energy conversion. © 2021 Wiley-VCH GmbH
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    Initial results of an intercomparison of AMS-based atmospheric 14CO2 measurements
    (Cambridge University Press, 2016-02-16) Miller, J; Lehman, SJ; Wolak, C; Turnbull, J; Dunn, G; Graven, H; Keeling, RF; Meijer, HAJ; Aerts-Bijma, AT; Palstra, SWL; Smith, AM; Allison, CE; Southon, J; Xu, XM; Nakazawa, T; Aoki, S; Nakamura, T; Guilderson, TP; LaFranchi, B; Mukai, M; Terao, Y; Uchida, M; Kondo, M
    This article presents results from the first 3 rounds of an international intercomparison of measurements of Δ14CO2 in liter-scale samples of whole air by groups using accelerator mass spectrometry (AMS). The ultimate goal of the intercomparison is to allow the merging of Δ14CO2 data from different groups, with the confidence that differences in the data are geophysical gradients and not artifacts of calibration. Eight groups have participated in at least 1 round of the intercomparison, which has so far included 3 rounds of air distribution between 2007 and 2010. The comparison is intended to be ongoing, so that: a) the community obtains a regular assessment of differences between laboratories; and b) individual laboratories can begin to assess the long-term repeatability of their measurements of the same source air. Air used in the intercomparison was compressed into 2 high-pressure cylinders in 2005 and 2006 at Niwot Ridge, Colorado (USA), with one of the tanks "spiked" with fossil CO2, so that the 2 tanks span the range of Δ14CO2 typically encountered when measuring air from both remote background locations and polluted urban ones. Three groups show interlaboratory comparability within 1‰ for ambient level Δ14CO2. For high CO2/low Δ14CO2 air, 4 laboratories showed comparability within 2‰. This approaches the goals set out by the World Meteorological Organization (WMO) CO2 Measurements Experts Group in 2005. One important observation is that single-sample precisions typically reported by the AMS community cannot always explain the observed differences within and between laboratories. This emphasizes the need to use long-term repeatability as a metric for measurement precision, especially in the context of long-term atmospheric monitoring. © 2013 by the Arizona Board of Regents on behalf of the University of Arizona.