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

NH3选择性催化氧化（SCO）是消除NH3排放的最佳方法之一。NH3-SCO的主要挑战是在宽的操作温度范围内实现高转化率，避免过度氧化成N2 O和N2。商业Pt催化剂在低温下具有完全的NH3转化率，但具有低的N2选择性。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相结合，将形成新的串联Pt-CuO/Al_2O_3和Pt-Pd/Al_2O_3催化剂，并有助于提高N_2的生成。通过原子级的精确改性，可以同时获得高的转化率和选择性。这将改变表面上的NH3吸附、N-N形成和O2活化，这可以通过一系列操作光谱（operando spectroscopy）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。将这些操作方法与密度泛函理论计算相结合，探索内选择性催化还原机理和N2-机理的可能中间体和反应途径。预计这些结果将为即将到来的Euro-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.