Liu Xiaoyan, Wu Jinfeng, Luo Zhuyu, Liu Ping, Tian Yue, Wang Xuewei, Li Hexing
The Education Ministry Key Lab of Resource Chemistry and Shanghai Key Laboratory of Rare Earth Functional Materials, College of Chemistry and Material Science, Shanghai Normal University, Shanghai 200234, China.
ACS Appl Mater Interfaces. 2023 Feb 7. doi: 10.1021/acsami.2c19713.
Oxygen reduction and evolution reactions (ORR and OER, respectively) are vital steps for metal-air batteries, which are plagued by their sluggish kinetics. It is still a challenge to develop highly effective and low-cost non-noble-metal-based electrocatalysts. Herein, a simple and reliable method was reported to synthesize a CoP-assisted Co single-atom (Co-N centers) electrocatalyst (CoP/Co-NC) via evaporative drying and pyrolysis processes. The CoP nanoparticles and Co-N centers are uniformly distributed on the nitrogen-doped carbon matrix. Notably, CoP/Co-NC showed excellent activities in both ORR (initial potential, 1.01 V; half-wave potential, 0.88 V) and OER (overpotential, 369 mV at 10 mA cm). The above results were comparable to those of commercial catalysts (such as Pt/C and RuO). Based on the experimental and theoretical analyses, the impressive activity can be ascribed to the tailored electronic structure of Co-N centers by the adjacent CoP, enabling the electron transfer from the Co atom to the neighboring C atoms, leading to a downshift of the d-band center, and improved reaction kinetics were achieved. The assembled Zn-air batteries using CoP/Co-NC as the air cathode showed a peak power density of 187 mW cm and long-life cycling stability for 140 h at 5 mA cm. This work may pave a promising avenue to design hybrid bifunctional electrocatalysts for highly efficient ORR/OER.
氧还原反应和析氧反应（分别为ORR和OER）是金属空气电池的关键步骤，但它们的动力学缓慢，存在诸多问题。开发高效且低成本的非贵金属基电催化剂仍然是一项挑战。在此，我们报道了一种简单可靠的方法，通过蒸发干燥和热解过程合成了一种CoP辅助的Co单原子（Co-N中心）电催化剂（CoP/Co-NC）。CoP纳米颗粒和Co-N中心均匀分布在氮掺杂碳基质上。值得注意的是，CoP/Co-NC在ORR（起始电位为1.01 V；半波电位为0.88 V）和OER（在10 mA cm时过电位为369 mV）中均表现出优异的活性。上述结果与商业催化剂（如Pt/C和RuO）相当。基于实验和理论分析，这种令人印象深刻的活性可归因于相邻CoP对Co-N中心电子结构的定制，使得电子从Co原子转移到相邻的C原子，导致d带中心下移，从而实现了反应动力学的改善。使用CoP/Co-NC作为空气阴极组装的锌空气电池在5 mA cm时显示出187 mW cm的峰值功率密度和140小时的长寿命循环稳定性。这项工作可能为设计用于高效ORR/OER的混合双功能电催化剂开辟一条有前景的途径。
