College of Materials and Chemistry & Chemical Engineering, Chengdu University of Technology, 1#, Dongsanlu, Erxianqiao, Chengdu 610059, Sichuan, PR China.
State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054, Sichuan, PR China.
J Colloid Interface Sci. 2023 Sep;645:439-447. doi: 10.1016/j.jcis.2023.04.128. Epub 2023 Apr 27.
Tailored electrocatalysts that can modulate their electronic structure are highly desirable to facilitate the reaction kinetics of oxygen evolution reaction (OER) and oxidation reduction reaction (ORR) in lithium-oxygen batteries (LOB). Although octahedron predominant inverse spinels (e.g., CoFeO) have been proposed as promising candidates for catalytic reactions, their performance has remained unsatisfactory. Herein, the chromium (Cr) doped CoFeO nanoflowers (Cr-CoFeO) are elaborately constructed on nickel foam as a bifunctional electrocatalyst that drastically improves the performance of LOB. The results show that the partially oxidized Cr stabilizes the cobalt (Co) sites at high-valence and regulates the electronic structure of Co sites, facilitating the oxygen redox kinetics of LOB due to their strong electron-withdrawing capability. Moreover, DFT calculations and ultraviolet photoelectron spectrometer (UPS) results consistently demonstrate that Cr doping optimizes the e electron filling state of the active octahedral Co sites, significantly improves the covalency of Co-O bonds, and enhances the degree of Co 3d-O 2p hybrids. As a result, Cr-CoFeO catalyzed LOB can achieve low overpotential (0.48 V), high discharge capacity (22030 mA h g) and long-term cycling durability (over 500 cycles at 300 mA g). This work promotes the oxygen redox reaction and accelerates the electron transfer between Co ions and oxygen-containing intermediates, highlighting the potential of Cr-CoFeO nanoflowers as bifunctional electrocatalysts for LOB.
在锂-氧电池（LOB）中，具有可调谐电子结构的定制电催化剂对于促进析氧反应（OER）和氧化还原反应（ORR）的反应动力学是非常理想的。尽管八面体为主的反尖晶石（例如 CoFeO）已被提议作为催化反应的有前途的候选物，但它们的性能仍然不尽人意。在此，通过在泡沫镍上精心构建掺杂铬（Cr）的 CoFeO 纳米花（Cr-CoFeO）作为双功能电催化剂，极大地提高了 LOB 的性能。结果表明，部分氧化的 Cr 将 Co 位稳定在高价态，并调节 Co 位的电子结构，由于其强的吸电子能力，从而促进 LOB 的氧氧化还原动力学。此外，密度泛函理论（DFT）计算和紫外光电子能谱（UPS）结果一致表明，Cr 掺杂优化了活性八面体 Co 位的 e 电子填充状态，显著提高了 Co-O 键的共价性，并增强了 Co 3d-O 2p 杂化的程度。因此，Cr-CoFeO 催化的 LOB 可以实现低过电位（0.48 V）、高放电容量（22030 mA h g）和长期循环耐久性（在 300 mA g 下超过 500 次循环）。这项工作促进了氧氧化还原反应，并加速了 Co 离子和含氧中间体之间的电子转移，突出了 Cr-CoFeO 纳米花作为 LOB 双功能电催化剂的潜力。
