Abbott Daniel F, Xu Yuan-Zi, Kuznetsov Denis A, Kumar Priyank, Müller Christoph R, Fedorov Alexey, Mougel Victor
Department of Chemistry and Applied Biosciences, ETH Zürich, Vladimir-Prelog-Weg 1-5, 8093, Zürich, Switzerland.
Department of Mechanical and Process Engineering, ETH Zürich, Leonhardstrasse 21, 8092, Zürich, Switzerland.
Angew Chem Int Ed Engl. 2023 Dec 18;62(51):e202313746. doi: 10.1002/anie.202313746. Epub 2023 Nov 15.
Mo- and Fe-containing enzymes catalyze the reduction of nitrate and nitrite ions in nature. Inspired by this activity, we study here the nitrate reduction reaction (NO RR) catalyzed by an Fe-substituted two-dimensional molybdenum carbide of the MXene family, viz., Mo CT : Fe (T are oxo, hydroxy and fluoro surface termination groups). Mo CT : Fe contains isolated Fe sites in Mo positions of the host MXene (Mo CT ) and features a Faradaic efficiency (FE) and an NH yield rate of 41 % and 3.2 μmol h mg , respectively, for the reduction of NO to NH in acidic media and 70 % and 12.9 μmol h mg in neutral media. Regardless of the media, Mo CT : Fe outperforms monometallic Mo CT owing to a more facile reductive defunctionalization of T groups, as evidenced by in situ X-ray absorption spectroscopy (Mo K-edge). After surface reduction, a T vacancy site binds a nitrate ion that subsequently fills the vacancy site with O* via oxygen transfer. Density function theory calculations provide further evidence that Fe sites promote the formation of surface O vacancies, which are identified as active sites and that function in NO RR in close analogy to the prevailing mechanism of the natural Mo-based nitrate reductase enzymes.
含钼和铁的酶在自然界中催化硝酸根离子和亚硝酸根离子的还原反应。受此活性启发，我们在此研究了由MXene族的铁取代二维碳化钼，即Mo CT : Fe（T为氧代、羟基和氟表面端基）催化的硝酸根还原反应（NO RR）。Mo CT : Fe在主体MXene（Mo CT）的钼位置含有孤立的铁位点，在酸性介质中将NO 还原为NH 时，其法拉第效率（FE）和NH产率分别为41 %和3.2 μmol h mg ，在中性介质中分别为70 %和12.9 μmol h mg 。无论在何种介质中，Mo CT : Fe均优于单金属Mo CT，这是由于T基团的还原去官能化更容易，原位X射线吸收光谱（Mo K边）证明了这一点。表面还原后，一个T空位位点结合一个硝酸根离子，该硝酸根离子随后通过氧转移用O*填充空位位点。密度泛函理论计算进一步证明，铁位点促进了表面氧空位的形成，这些氧空位被确定为活性位点，并且在NO RR中的作用与天然钼基硝酸还原酶的普遍机制非常相似。
