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

NH3选择性催化氧化制N2是消除NH3排放的最佳途径之一。NH3-SCO的一个主要挑战是在广泛的工作温度范围内实现高转化率，避免过度氧化为N2O和N2。商品Pt催化剂在低温下NH3转化率高，但N2选择性低。为了缓解这一挑战，限制NH3的过度氧化至关重要。研究人员提出，通过将高活性Pt与高选择性Cu或Pd结合，将形成新的Pt- cuo /Al2O3和Pt-Pd/Al2O3串联催化剂，并有助于改善N2的形成。通过对双金属催化剂进行原子级修饰，可以同时实现高转化率和高选择性。这将改变NH3在表面的吸附、N-N的形成和O2的活化，这可以通过一系列的operando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。利用这些方法结合密度泛函理论计算，探索内部选择性催化还原机理和N2-机理可能的中间体和反应途径。研究结果有望为即将到来的欧七法规提供解决方案，该法规将于2025年起对NH3排放生效。

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.