Rodney Smith1
University of Waterloo1
Transition metal ions in undercoordinated sites, such as edge-sites in layered double hydroxides or adjacent to oxygen vacancies in perovskites, have long been envisioned as catalytically relevant sites for electrochemical reactions such as the oxygen evolution reaction. Direct analysis of such defect chemistry in solid state electrocatalysts is impeded by the low concentrations of defects relative to bulk sites, multitude of viable defects in any given material, potential for dynamic changes during catalysis, and fundamental limitations inherent in every characterization technique. We pursue experimental evidence for strained, distorted, or defective coordination environments in common electrocatalysts such that we can systematically identify and rule out specific features as catalytically relevant sites to guide efforts to design improved catalysts. Our strategy is to combine systematic variations in synthesis with comprehensive characterization. Synthetic strategies are developed to prepare series of samples that, ideally, are dominated by changes in a single type of structural disorder. The structure, properties, and electrochemical parameters extracted from diverse techniques are then comprehensively compared to each other to identify useful structure-property and structure-structure correlations. These correlations can provide chemical insights that cannot otherwise be attained. This talk will demonstrate how this strategy enabled identification of distortions and unreported coordination environments in iron-nickel hydroxide,<sup>1,2</sup> and defects such as interstitial protons and associated iron vacancies in hematite photoanodes.<sup>3,4</sup><br/><br/>(1) Alsaç, E. P.; Zhou, K.; Rong, W.; Salamon, S.; Landers, J.; Wende, H.; Smith, R. D. L. <i>Energy Environ. Sci.</i> <b>2022</b>, <i>15</i> (6), 2638–2652.<br/>(2) Alsaç, E. P.; Smith, R. D. L. <i>ACS Catal.</i> <b>2022</b>, <i>12</i> (19), 12419–12431.<br/>(3) Liu, Y.; Smith, R. D. L. <i>ACS Appl. Mater. Interfaces</i> <b>2022</b>, <i>14</i> (5), 6615–6624.<br/>(4) Liu, Y.; Smith, R. D. L. <i>Chem. Sci.</i> <b>2020</b>, <i>11</i> (4), 1085–1096.