Pt-Rh alloy nanoparticles on oxide supports are widely employed in heterogeneous catalysis with applications ranging from automotive exhaust control to energy conversion. To improve catalyst performance, an atomic-scale correlation of the nanoparticle surface structure with its catalytic activity under industrially relevant operando conditions is essential. Here, we present x-ray diffraction data sensitive to the nanoparticle surface structure combined with in situ mass spectrometry during near ambient pressure CO oxidation. We identify the formation of ultrathin surface oxides by detecting x-ray diffraction signals from particular nanoparticle facets and correlate their evolution with the sample’s enhanced catalytic activity. Our approach opens the door for an in-depth characterization of well-defined, oxide-supported nanoparticle based catalysts under operando conditions with unprecedented atomic-scale resolution.

氧化物载体上的Pt-Rh合金纳米粒子广泛用于非均相催化中，其应用范围从汽车排气控制到能量转换。为了提高催化剂性能，在工业上相关的操作条件下，纳米颗粒表面结构与其催化活性的原子尺度相关性是必不可少的。在这里，我们提出了对纳米颗粒表面结构敏感的x射线衍射数据，并结合原位在接近环境压力CO氧化过程中进行质谱分析。我们通过检测特定纳米粒子刻面的X射线衍射信号来识别超薄表面氧化物的形成，并将其演变与样品增强的催化活性相关联。我们的方法为在操作条件下以前所未有的原子级分辨率对定义明确的，氧化物负载的基于纳米颗粒的催化剂进行深入表征打开了大门。