Defects may display high reactivity because the specific arrangement of atoms differs from crystalline surfaces. We demonstrate that high-temperature steam pretreatment of palladium catalysts provides a 12-fold increase in the mass-specific reaction rate for carbon-hydrogen (C–H) activation in methane oxidation compared with conventional pretreatments. Through a combination of experimental and theoretical methods, we demonstrate that an increase in the grain boundary density through crystal twinning is achieved during the steam pretreatment and oxidation and is responsible for the increased reactivity. The grain boundaries are highly stable during reaction and show specific rates at least two orders of magnitude higher than other sites on the palladium on alumina (Pd/Al₂O₃) catalysts. Theoretical calculations show that strain introduced by the defective structure can enhance C–H bond activation. Introduction of grain boundaries through laser ablation led to further rate increases.

中文翻译：

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用于钯催化剂中甲烷 C-H 活化的蒸汽产生的晶界

缺陷可能表现出高反应性，因为原子的特定排列与晶体表面不同。我们证明，与传统预处理相比，钯催化剂的高温蒸汽预处理使甲烷氧化中碳-氢 (C-H) 活化的质量比反应速率提高了 12 倍。通过实验和理论方法的结合，我们证明了通过晶体孪晶增加晶界密度是在蒸汽预处理和氧化过程中实现的，并且是反应性增加的原因。_{晶界在反应过程中高度稳定，比氧化铝上钯上的其他位点（Pd/Al 2} O ₃）显示出至少两个数量级的比速率。) 催化剂。理论计算表明，缺陷结构引入的应变可以增强 C-H 键的活化。通过激光烧蚀引入晶界导致速率进一步提高。