Liu Sisi, Wang Mengfan, Qian Tao, Ji Haoqing, Liu Jie, Yan Chenglin
College of Energy, Key Laboratory of Advanced Carbon Materials and Wearable Energy Technologies of Jiangsu Province, Soochow University, Suzhou, 215006, China.
Nat Commun. 2019 Aug 29;10(1):3898. doi: 10.1038/s41467-019-11846-x.
Covalent organic frameworks with abundant active sites are potential metal-free catalysts for the nitrogen reduction reaction. However, the utilization ratio of active sites is restricted in an actual reaction process due to the limited nitrogen transport. Here, we demonstrate that facilitating the N accessibility to boron-rich covalent organic frameworks through electrochemical excitation can achieve highly efficient nitrogen reduction activity. Simulations show that the boron sites are bonded with nitrogenous species under electrochemical condition and the resultant amorphous phase of covalent organic frameworks has much stronger affinity toward N to enhance the molecule collision. Combined with experimental results, the excitation process is confirmed to be a virtuous cycle of more excited sites and stronger N affinity, which continuously proceed until the whole system reaches the optimum reaction status. As expected, the electrochemically excited catalyst delivers significantly enhanced reaction activity, with a high Faradaic efficiency of 45.43%.
具有丰富活性位点的共价有机框架是用于氮还原反应的潜在无金属催化剂。然而，由于氮传输受限，在实际反应过程中活性位点的利用率受到限制。在此，我们证明通过电化学激发促进氮与富硼共价有机框架的接触可以实现高效的氮还原活性。模拟表明，在电化学条件下硼位点与含氮物种结合，并且由此产生的共价有机框架非晶相对氮具有更强的亲和力，从而增强分子碰撞。结合实验结果，证实激发过程是一个更多激发位点和更强氮亲和力的良性循环，该循环持续进行直到整个系统达到最佳反应状态。正如预期的那样，电化学激发的催化剂具有显著增强的反应活性，法拉第效率高达45.43%。
