Zhang Wuyong, Zhan Shaoqi, Qin Qing, Heil Tobias, Liu Xiyu, Hwang Jinyeon, Ferber Thimo H, Hofmann Jan P, Oschatz Martin
Max Planck Institute of Colloids and Interfaces, Department of Colloid Chemistry, Am Mühlenberg 1, 14476, Potsdam, Germany.
Center for Energy and Environmental Chemistry Jena (CEEC Jena), Institute for Technical Chemistry and Environmental Chemistry, Friedrich-Schiller-University Jena, Philosophenweg 7a, 07743, Jena, Germany.
Small. 2022 Oct;18(42):e2204116. doi: 10.1002/smll.202204116. Epub 2022 Sep 16.
The electrochemical nitrogen reduction reaction (NRR) to ammonia (NH ) is a potentially carbon-neutral and decentralized supplement to the established Haber-Bosch process. Catalytic activation of the highly stable dinitrogen molecules remains a great challenge. Especially metal-free nitrogen-doped carbon catalysts do not often reach the desired selectivity and ammonia production rates due to their low concentration of NRR active sites and possible instability of heteroatoms under electrochemical potential, which can even contribute to false positive results. In this context, the electrochemical activation of nitrogen-doped carbon electrocatalysts is an attractive, but not yet established method to create NRR catalytic sites. Herein, a metal-free C N material (HAT-700) is electrochemically etched prior to application in NRR to form active edge-sites originating from the removal of terminal nitrile groups. Resulting activated metal-free HAT-700-A shows remarkable catalytic activity in electrochemical nitrogen fixation with a maximum Faradaic efficiency of 11.4% and NH yield of 5.86 µg mg h . Experimental results and theoretical calculations are combined, and it is proposed that carbon radicals formed during activation together with adjacent pyridinic nitrogen atoms play a crucial role in nitrogen adsorption and activation. The results demonstrate the possibility to create catalytically active sites on purpose by etching labile functional groups prior to NRR.
将电化学氮还原反应（NRR）转化为氨（NH₃）是对成熟的哈伯-博施法进行潜在的碳中和且分散式补充。高度稳定的双氮分子的催化活化仍然是一个巨大挑战。尤其是无金属的氮掺杂碳催化剂，由于其NRR活性位点浓度低以及在电化学势下杂原子可能不稳定，往往无法达到所需的选择性和氨生成速率，这甚至可能导致假阳性结果。在此背景下，氮掺杂碳电催化剂的电化学活化是一种有吸引力但尚未确立的创建NRR催化位点的方法。在此，一种无金属的C₃N₄材料（HAT-700）在用于NRR之前进行电化学蚀刻，以形成源自末端腈基去除的活性边缘位点。所得活化的无金属HAT-700-A在电化学固氮中表现出显著的催化活性，最大法拉第效率为11.4%，NH₃产率为5.86 μg mg⁻¹ h⁻¹。结合实验结果和理论计算，提出活化过程中形成的碳自由基与相邻的吡啶氮原子在氮吸附和活化中起关键作用。结果表明，在NRR之前通过蚀刻不稳定的官能团来有意创建催化活性位点是可能的。
