School of Materials Science and Engineering , Nanyang Technological University , Singapore 639798 , Singapore.
School of Chemical, Biological, and Environmental Engineering , Oregon State University , Corvallis , Oregon 97331 , United States.
ACS Appl Mater Interfaces. 2019 Apr 3;11(13):12941-12947. doi: 10.1021/acsami.8b21301. Epub 2019 Mar 22.
Epitaxial strain can cause both lattice distortion and oxygen nonstoichiometry, effects that are strongly coupled at heterojunctions of complex nickelate oxides. Here we decouple these structural and chemical effects on the oxygen evolution reaction (OER) by using a set of coherently strained epitaxial NdNiO films. We show that within the regime where oxygen vacancies (V) are negligible, compressive strain is favorable for the OER whereas tensile strain is unfavorable; the former induces orbital splitting, resulting in a higher occupancy in the d orbital and weaker Ni-O chemisorption. However, when the tensile strain is sufficiently large to promote V formation, an increase in the OER is also observed. The partial reduction of Ni to Ni due to V makes the e occupancy slightly larger than unity, which is thought to account for the increased OER activity. Our work highlights that epitaxial-strain-induced lattice distortion and V generation can be individually or collectively exploited to tune OER activity, which is important for the predictive synthesis of high-performance electrocatalysts.
外延应变既可以导致晶格畸变，也可以导致氧非化学计量，在复杂镍酸盐氧化物的异质结中，这两种效应是强烈耦合的。在这里，我们通过使用一系列相干应变外延 NdNiO 薄膜，将这些结构和化学效应对析氧反应（OER）的影响分离开来。我们表明，在氧空位（V）可以忽略不计的范围内，压缩应变有利于 OER，而拉伸应变不利于 OER；前者诱导轨道分裂，导致 d 轨道占据更高，Ni-O 化学吸附更弱。然而，当拉伸应变足够大以促进 V 的形成时，也观察到 OER 的增加。由于 V 的形成，Ni 部分还原为 Ni，使 e 占据数略大于 1，这被认为是增加 OER 活性的原因。我们的工作强调了外延应变诱导的晶格畸变和 V 的产生可以单独或共同被利用来调节 OER 活性，这对于高性能电催化剂的预测性合成是很重要的。
