Yang Xiecheng, Su Fengmei, Hou Minjie, Zhang Da, Dai Yongnian, Liang Feng
Faculty of Metallurgical and Energy Engineering, Kunming University of Science and Technology, Kunming 650093, China.
Faculty of Metallurgical and Energy Engineering, Kunming University of Science and Technology, Kunming 650093, China and State Key Laboratory of Complex Nonferrous Metal Resources Clean Utilization, Kunming University of Science and Technology, Kunming 650093, China.
Dalton Trans. 2021 May 25;50(20):7041-7047. doi: 10.1039/d1dt00807b.
The rational design of efficient and durable electrocatalysts to accelerate sluggish oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) kinetics is highly desirable for enhancing the efficiency of fuel cells and metal-air batteries. Here, we demonstrated a low-temperature plasma strategy at atmospheric pressure for enhancing the catalytic activity of metal-organic framework derived N-doped carbon nanotubes (MOF-NCNTs) by changing the relative contents of Co-Nx sites, Co-Co bonds and pyridinic-N. The increase of pyridinic-N/pyrrolic-N ratio improves the ORR performance, while unsaturated Co-Nx sites and strong Co-Co bonds promote the OER performance. The relative contents of pyridinic-N, Co-Nx sites, and Co-Co bonds in MOF-NCNTs can be readily tailored by varying the plasma treatment time. The MOF-NCNTs treated with N2 plasma for 4 min (MOF-NCNTs-N2-4) exhibited improved ORR (ηonset: 0.91 V) and OER (η10: 0.44 V) activities compared to MOF-NCNTs because of the higher ratio of pyridinic-N to pyrrolic-N and higher relative contents of Co-Nx sites and Co-Co bonds. The hybrid sodium-air batteries (HSABs) assembled with MOF-NCNTs-N2-4 catalyst display a low overpotential of 0.35 V and excellent round trip efficiency of 88.9% at 0.1 mA cm-2. Besides, they also exhibited great cycling stability with an average discharge voltage of 2.75 V and an outstanding round trip efficiency of 84% after 150 cycles.
合理设计高效耐用的电催化剂以加速缓慢的氧还原反应（ORR）和析氧反应（OER）动力学，对于提高燃料电池和金属空气电池的效率非常必要。在此，我们展示了一种大气压下的低温等离子体策略，通过改变Co-Nx位点、Co-Co键和吡啶氮的相对含量来提高金属有机框架衍生的氮掺杂碳纳米管（MOF-NCNTs）的催化活性。吡啶氮/吡咯氮比例的增加提高了ORR性能，而不饱和Co-Nx位点和强Co-Co键促进了OER性能。通过改变等离子体处理时间，可以轻松调整MOF-NCNTs中吡啶氮、Co-Nx位点和Co-Co键的相对含量。与MOF-NCNTs相比，用N2等离子体处理4分钟的MOF-NCNTs（MOF-NCNTs-N2-4）表现出改善的ORR（起始过电位：0.91 V）和OER（10 mA cm-2时的过电位：0.44 V）活性，这是因为吡啶氮与吡咯氮的比例更高，以及Co-Nx位点和Co-Co键的相对含量更高。用MOF-NCNTs-N2-4催化剂组装的混合钠空气电池（HSABs）在0.1 mA cm-2时显示出0.35 V的低过电位和88.9%的优异往返效率。此外，它们还表现出出色的循环稳定性，在150次循环后平均放电电压为2.75 V，往返效率高达84%。
