Elucidation of redox mechanism is vital to develop highly active catalysts for selective catalytic reduction (SCR) of NOx. Here, we apply an integrated experimental and theoretical approach to investigate low-temperature SCR (LT-SCR) mechanism over VOx/CeO₂, a model system containing industrially-relevant vanadia active-species and an eye-catching redox support, i.e. ceria, frequently documented in SCR studies. We show that NO oxidative activation to a gaseous nitrite-precursor intermediate, which was trapped by BaO/Al₂O₃ and further spectroscopically and computationally validated, serves as a key step in LT-SCR. This scheme involves paired contributions from vanadia and ceria, in which vanadium stabilizes at +5 while Ce³⁺/Ce⁴⁺ varies in the redox cascade, and coupling of V⁵⁺−OH and proximal Ce⁴⁺−O reduces the NO oxidative activation barrier. These findings progress the understanding of LT-SCR mechanism and deliver a specific perspective on the synergy of surface active-sites and supports, which are essential for the design of further improved SCR catalysts.

阐明氧化还原机理对于开发用于NOx选择性催化还原（SCR）的高活性催化剂至关重要。在这里，我们采用综合的实验和理论方法研究VOx / CeO _2上的低温SCR（LT-SCR）机理，该模型系统包含与工业相关的钒活性物质和醒目的氧化还原支持物，即氧化铈，经常在SCR研究中记录。我们表明，NO氧化活化为气态亚硝酸盐前体中间体，该中间体被BaO / Al ₂ O ₃捕集并经光谱和计算验证，是LT-SCR中的关键步骤。该方案涉及钒和二氧化铈的成对贡献，其中钒稳定在+5，而Ce ³⁺ / Ce⁴⁺在氧化还原级联中有所不同，并且V ⁵⁺ -OH和近端Ce ⁴⁺ -O的偶联降低了NO的氧化激活势垒。这些发现促进了对LT-SCR机理的理解，并提供了有关表面活性部位和载体协同作用的特定视角，这对于进一步改进SCR催化剂的设计至关重要。