‡Department of Chemistry, University of Washington, Seattle, Washington 98195-1700, United States.
§Department of Chemistry, Yale University, P.O. Box 208107, 225 Prospect Street, New Haven, Connecticut 06520-8107, United States.
J Am Chem Soc. 2015 Apr 8;137(13):4296-9. doi: 10.1021/jacs.5b00359. Epub 2015 Mar 30.
Several substituted iron-porphyrin complexes were evaluated for oxygen reduction reaction (ORR) electrocatalysis in different homogeneous and heterogeneous media. The selectivity for four-electron reduction to H2O versus two-electron reduction to H2O2 varies substantially from one medium to another for a given catalyst. In many cases, the influence of the medium in which the catalyst is evaluated has a larger effect on the observed selectivity than the factors attributable to chemical modification of the catalyst. For instance, introduction of potential proton relays has variable effects depending on the catalyst medium. Thus, comparisons of selectivity results from supported and soluble molecular ORR electrocatalysts must be interpreted with caution, as selectivity is a property not only of the catalyst, but also of the larger mesoscale environment beyond the catalyst. Still, in all the direct pairwise comparisons in the same medium, the catalysts with potential proton relays have similar or better selectivity for the preferred 4e(-) path.
几种取代的铁卟啉配合物在不同的均相和多相介质中被评估用于氧还原反应（ORR）电催化。对于给定的催化剂，从一种介质到另一种介质，对于四电子还原为 H2O 与两电子还原为 H2O2 的选择性有很大的变化。在许多情况下，催化剂评估的介质的影响比对催化剂化学修饰归因的因素对观察到的选择性的影响更大。例如，引入潜在的质子传递体取决于催化剂介质而具有不同的效果。因此，必须谨慎解释负载型和可溶性分子 ORR 电催化剂的选择性结果之间的比较，因为选择性不仅是催化剂的特性，而且也是催化剂之外的更大的介观环境的特性。尽管如此，在相同介质中的所有直接成对比较中，具有潜在质子传递体的催化剂对于首选的 4e(-) 途径具有相似或更好的选择性。
