Tandem Catalysts Design towards Efficient Selective Catalytic Oxidation of ammonia (TCatSCO)

NH3选择性催化氧化(SCO)是消除NH3排放的最好方法之一。NH3-SCO的一个主要挑战是在较宽的工作温度范围内实现高转化率，避免过度氧化为N2O和N2。工业铂催化剂在低温下具有完全的NH3转化能力，但氮气选择性较低。为了缓解这一挑战，限制NH3的过氧化至关重要。研究人员提出，通过将高活性的铂与高选择性的铜或钯相结合，新的串联铂-CuO/氧化铝和铂-钯/氧化铝催化剂将形成并有助于改善氮气的生成。通过对双金属催化剂进行原子级的精确修饰，可以同时实现高转化率和高选择性。这将改变NH3的吸附、N-N的形成和O2在表面的活化，这可以通过一系列的操作面光谱来探测，包括X射线吸收精细结构、X射线发射、红外和电子顺磁共振。并结合密度泛函理论计算，对可能的中间体和反应途径进行了探讨。预计这一结果将为即将出台的欧盟-7法规提供解决方案，该法规从2025年起对NH3排放有效。

Selective catalytic oxidation (SCO) of NH3 to N2 is one of the best ways to eliminate NH3 emissions. A major challenge in NH3-SCO is to achieve high conversion for a wide operating temperature range, avoiding over-oxidation to N2O and N2. The commercial Pt catalysts have full NH3 conversion at low temperatures but suffer from low N2 selectivity. To mitigate this challenge, it is crucial to limit the overoxidation of NH3. The researcher proposes that by integrating highly active Pt with highly selective Cu or Pd, new tandem Pt-CuO/Al2O3 and Pt-Pd/Al2O3 catalysts will form and help improve the N2 formation. The simultaneously high conversion and selectivity can be achieved by modifying the bimetallic catalysts with atomic-level precision. This will change the NH3 adsorption, N-N formation and the O2 activation on the surface, which can be probed via a series of operando spectroscopy, including X-ray absorption fine structure, X-ray emission, Infrared, and electron paramagnetic resonance. The possible intermediates and reaction pathways for internal selective catalytic reduction mechanism and N2- mechanism will be explored with those operando methods combined with density-functional theory calculations. The results are expected to provide a solution towards the upcoming Euro-7 regulations, which are valid from 2025 onwards for NH3 emissions.