Single-atom alloy (SAA) catalysts exhibit unique and excellent catalytic properties in heterogeneous hydrogenation/dehydrogenation reactions. A thorough understanding of the microscopic surface processes is essential to improve the catalytic performance. Here, from a new perspective of the temperature-programmed desorption (TPD) spectra of hydrogen (H) on two common SAA surfaces, Pt@Cu(111) and Pd@Cu(111), we reveal and confirm the key influence of H atoms attached to Pt/Pd dopants, i.e., the H atom bystander, on the desorption process of surface H atoms. It is found that only after considering the effect of the H atom bystander can the simulated TPD spectra well reproduce the experimentally observed higher desorption temperature on Pt@Cu(111) than on Pd@Cu(111) and the leftward shift of the TPD peak with increasing H atom coverage; otherwise, the features are inconsistent with experiments. Our work provides direct evidence for the effect of bystander H atoms from a simulation perspective.

中文翻译：

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旁观者氢原子对单原子合金表面氢解吸的影响：来自模拟程序升温解吸光谱的见解

单原子合金（SAA）催化剂在非均相加氢/脱氢反应中表现出独特且优异的催化性能。彻底了解微观表面过程对于提高催化性能至关重要。在这里，从两个常见 SAA 表面 Pt@Cu(111) 和 Pd@Cu(111) 上氢 (H) 的程序升温脱附 (TPD) 谱的新角度，我们揭示并证实了 H 的关键影响附着在 Pt/Pd 掺杂剂上的原子（即 H 原子旁观者）对表面 H 原子解吸过程的影响。结果发现，只有考虑H原子旁观者的影响，模拟的TPD谱才能很好地再现实验观察到的Pt@Cu(111)上比Pd@Cu(111)上更高的解吸温度以及TPD峰左移随着H原子覆盖率的增加；否则，特征与实验不一致。我们的工作从模拟的角度为旁观者氢原子的影响提供了直接证据。