Enhanced Ammonia Synthesis Activity of Ceria-Supported Ruthenium Catalysts Induced by CO Activation

Metal-support interactions strongly affect the catalytic performances of ceria-supported metal catalysts, and hydrogen treatment at high temperature is important for the preparation of catalysts that show strong metal-support interaction (SMSI). With SMSI, the proportion of metal species existing in the form of a metallic state is lowered, consequently hindering the performance of a metal catalyst for a reaction that requires metallic sites. Here we show that CO activation of a Ru/CeO2 catalyst not only enhances the reduction degree and exposure of Ru species but also increases Ce2+ concentration, oxygen vacancy (O-V), and active oxygen, resulting in the formation of electron-enriched Ru delta- species and Ru delta-OV-Ce3+ sites. As a result, a Ru/CeO2 catalyst after CO activation shows high ammonia synthesis activity, and the ill effect of hydrogen poisoning is effectively alleviated. These findings are important for the design of supported metal catalysts that afford metallic species as active sites.

金属 - 载体相互作用强烈影响负载在二氧化铈上的金属催化剂的催化性能，高温氢气处理对于制备具有强金属 - 载体相互作用（SMSI）的催化剂非常重要。具有SMSI时，以金属态形式存在的金属物种的比例会降低，从而阻碍了金属催化剂在需要金属位点的反应中的性能。在此我们表明，Ru/CeO₂催化剂的CO活化不仅提高了Ru物种的还原程度和暴露程度，还增加了Ce²⁺浓度、氧空位（O - V）和活性氧，导致形成富电子的Ruδ - 物种和Ruδ - OV - Ce³⁺位点。因此，CO活化后的Ru/CeO₂催化剂显示出高的氨合成活性，并且氢中毒的不良影响得到有效缓解。这些发现对于设计以金属物种作为活性位点的负载型金属催化剂具有重要意义。