Yang Xuan, Nash Jared, Anibal Jacob, Dunwell Marco, Kattel Shyam, Stavitski Eli, Attenkofer Klaus, Chen Jingguang G, Yan Yushan, Xu Bingjun
Center for Catalytic Science and Technology, Department of Chemical and Biomolecular Engineering , University of Delaware , 150 Academy Street , Newark , Delaware 19716 , United States.
Department of Chemical Engineering , Columbia University , New York , New York 10027 , United States.
J Am Chem Soc. 2018 Oct 17;140(41):13387-13391. doi: 10.1021/jacs.8b08379. Epub 2018 Oct 5.
Renewable production of ammonia, a building block for most fertilizers, via the electrochemical nitrogen reduction reaction (ENRR) is desirable; however, a selective electrocatalyst is lacking. Here we show that vanadium nitride (VN) nanoparticles are active, selective, and stable ENRR catalysts with an ENRR rate and a Faradaic efficiency (FE) of 3.3 × 10 mol s cm and 6.0% at -0.1 V within 1 h, respectively. ENRR with N as the feed produces both NH and NH, which indicates that the reaction follows a Mars-van Krevelen mechanism. Ex situ X-ray photoelectron spectroscopy characterization of fresh and spent catalysts reveals that multiple vanadium oxide, oxynitride, and nitride species are present on the surface and identified VNO as the active phase in the ENRR. Operando X-ray absorption spectroscopy and catalyst durability test results corroborate this hypothesis and indicate that the conversion of VNO to the VN phase leads to catalyst deactivation. We hypothesize that only the surface N sites adjacent to a surface O are active in the ENRR. An ammonia production rate of 1.1 × 10 mol s cm can be maintained for 116 h, with a steady-state turnover number of 431.
通过电化学氮还原反应（ENRR）可再生生产氨（大多数肥料的组成成分）是很理想的；然而，目前缺乏一种选择性电催化剂。在此我们表明，氮化钒（VN）纳米颗粒是活性高、选择性好且稳定的ENRR催化剂，在-0.1 V下1小时内的ENRR速率和法拉第效率（FE）分别为3.3×10⁻⁹ mol s⁻¹ cm⁻²和6.0%。以N₂为原料的ENRR会同时产生NH₃和NH₂OH，这表明该反应遵循Mars-van Krevelen机制。对新鲜催化剂和用过的催化剂进行的非原位X射线光电子能谱表征表明，表面存在多种钒氧化物、氮氧化物和氮化物物种，并确定VNO为ENRR中的活性相。原位X射线吸收光谱和催化剂耐久性测试结果证实了这一假设，并表明VNO向VN相的转变会导致催化剂失活。我们推测，在ENRR中只有与表面O相邻的表面N位点具有活性。氨的生成速率为1.1×10⁻⁹ mol s⁻¹ cm⁻²，可维持116小时，稳态周转数为431。
