Preferential oxidation (PROX) of carbon monoxide (CO) in presence of excess hydrogen is a necessity to prevent poisoning of the Pt-anode by CO in PEMFCs (Polymer Electrolyte Membrane Fuel Cell). A highly active catalyst, 5 wt% Cu-CeO₂ showed 100 % CO conversion at 65 °C without any undesirable oxidation of H₂. The catalyst showed no deactivation even after 100 h on stream, making it viable for practical fuel cell application. Operando EPR in the PROX reaction condition revealed highly dispersed mixed valent cations with oxygen vacancies, responsible for the low-temperature PROX activity. At the active site, both Cu and Ce ions were shown to reversibly change their valence states to facilitate the abstraction of bridging lattice oxygen for CO oxidation to CO₂. This surface oxygen mediated CO oxidation was found to be much faster than that of H₂ to H₂O, which could explain the complete selectivity of oxygen for CO₂ formation.

在过量氢气存在下，一氧化碳 (CO) 的优先氧化 (PROX) 是防止 Pt 阳极被 PEMFC（聚合物电解质膜燃料电池）中的 CO 中毒的必要条件。一种高活性催化剂，5 wt% Cu-CeO ₂在 65 °C 下显示出 100% 的 CO 转化率，而没有任何不希望的 H ₂氧化。该催化剂即使在运行 100 小时后也没有失活，使其可用于实际燃料电池应用。PROX 反应条件下的 Operando EPR 显示高度分散的混合价阳离子与氧空位，负责低温 PROX 活性。在活性位点，Cu 和 Ce 离子都显示出可逆地改变它们的价态，以促进从 CO 氧化为 CO ₂的桥接晶格氧的提取. 发现这种表面氧介导的 CO 氧化比 H ₂氧化为 H ₂ O快得多，这可以解释氧对 CO ₂形成的完全选择性。