Materials Science and Technology Division, Oak Ridge National Laboratory, 1 Bethel Valley Rd., P.O. Box 2008 MS-6114, Bldg.: 4100, Rm: B375, Oak Ridge, TN 37831, USA.
Phys Chem Chem Phys. 2019 Feb 27;21(9):4738-4745. doi: 10.1039/c8cp02405g.
The slow kinetics of the oxygen evolution (OER) and oxygen reduction (ORR) reactions hamper the development of renewable energy storage and conversion technologies. Transition-metal oxides (TMOs) are cost-effective replacements to conventional noble metal catalysts for driving these electrochemical systems. Strain is known to greatly affect the electronic structure of TMO surfaces, leading to significant changes in their electrocatalytic activities. In this study, we explore the influence of strain on the OER and ORR mechanisms on the LaNiO3(001) surface using density functional theory (DFT). Through a comparison of the overpotential and the largest change in Gibbs free energy (ΔG) in the reaction pathway, we determined that the OER activity on the LaNiO3 surface is directly related to the desorption of -H from the surface, which can be tuned as a function of strain. Moreover, tensile strain shuts off the reaction pathway to forming the -O2H intermediate state, due to the dissociation of -O2H into -O2 and -H. This is largely a consequence of the strong binding of H to the surface O, leading to a significant increase in the largest ΔG for the ORR on the tensile-strained surfaces by promoting an alternative reaction pathway. Overall, our results show that tensile strain on LaNiO3(001) leads to a decrease in both OER and ORR activities. Interestingly, in both cases, we find that the reaction is driven by the interactions with surface O ions, thus calling for a reinterpretation of the role that Ni eg orbital polarization plays in defining the OER and ORR catalytic activity on the TMO surfaces. Here, it is an indirect measure of changes in Ni-O hybridization, which controls the binding of -H species to the surface. As such, these results highlight the importance of surface O ions; particularly as it relates to defining molecule-surface interactions that ultimately tune and enhance the electrocatalytic efficiency of perovskite materials through the modulation of strains.
氧析出反应（OER）和氧还原反应（ORR）的缓慢动力学阻碍了可再生能源存储和转换技术的发展。过渡金属氧化物（TMOs）是驱动这些电化学系统的传统贵金属催化剂的经济有效的替代品。应变已知会极大地影响 TMO 表面的电子结构，导致其电催化活性发生显著变化。在这项研究中，我们使用密度泛函理论（DFT）研究了应变对 LaNiO3（001）表面 OER 和 ORR 机制的影响。通过比较过电势和反应途径中吉布斯自由能（ΔG）的最大变化，我们确定 LaNiO3 表面的 OER 活性与表面上 -H 的解吸直接相关，这可以作为应变的函数进行调节。此外，拉伸应变会阻止 -O2H 中间态的形成反应途径，这是由于 -O2H 分解为 -O2 和 -H。这主要是由于 H 与表面 O 的强结合，导致拉伸应变表面上 ORR 的最大 ΔG 显著增加，从而促进了替代反应途径。总的来说，我们的结果表明，LaNiO3（001）上的拉伸应变导致 OER 和 ORR 活性均降低。有趣的是，在这两种情况下，我们发现反应都是由与表面 O 离子的相互作用驱动的，因此需要重新解释 Ni eg 轨道极化在定义 TMO 表面的 OER 和 ORR 催化活性中的作用。在这里，它是 Ni-O 杂化变化的间接度量，控制 -H 物种与表面的结合。因此，这些结果强调了表面 O 离子的重要性；特别是与定义分子-表面相互作用有关，这些相互作用最终通过调节应变来调节和提高钙钛矿材料的电催化效率。
