Supported precious metals with atomic dispersion are of great interest in catalysis due to their potentials in achieving maximum atom efficiency and unique reactivities. Herein, the active sites for low-temperature CO oxidation are elucidated over single-atom Pd₁/CeO₂ catalysts prepared via high-temperature atom trapping (AT). The increased oxygen vacancies on CeO₂ surface induced by 800 °C air calcination result in decreased Pd–CeO₂ coordinations, i.e., the coordination-unsaturated Pd²⁺ on CeO₂. Light-off and light-out measurements coupled with CO-DRIFTS and X-ray absorption characterization confirm that these coordination-unsaturated Pd²⁺ on CeO₂ are much more reactive than the fully coordinated counterpart, evidenced by a decrease of T₉₀ (temperature to achieve 90% conversion) by ∼100 °C in CO oxidation at a gas hourly space velocity of 300 L g^–1 h^–1.

中文翻译：

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低温CO氧化单原子Pd ₁ / CeO ₂催化剂中活性位的阐明

具有原子分散性的负载型贵金属具有催化作用，因为它们具有实现最大原子效率和独特反应性的潜力。在此，在通过高温原子俘获（AT）制备的单原子Pd ₁ / CeO ₂催化剂上阐明了低温CO氧化的活性位点。上的CeO增加氧空位₂通过800℃空气中煅烧结果诱导的表面下降的Pd-的CeO _2个配位，即，配位不饱和的Pd ²⁺上的CeO ₂。起燃和熄灭测量与CO-DRIFTS和X射线吸收特征相结合证实了CeO上这些配位不饱和的Pd ²⁺₂的反应性比完全协调的对应物要强得多，这在气体每小时空速300 L g ^–1 h ^{–1的条件}下在CO氧化中将T ₉₀（达到90％转化的温度）降低了约100°C 。