Armillotta Francesco, Naderasli Pardis, Chesnyak Valeria, Brune Harald
Ecole Polytechnique Fédérale de Lausanne (EPFL), Station 3, CH-1015 Lausanne, Switzerland.
Physics Department, University of Trieste, via A.Valerio 2, 34127 Trieste, Italy.
J Phys Chem C Nanomater Interfaces. 2024 Dec 25;129(10):4915-4922. doi: 10.1021/acs.jpcc.4c07088. eCollection 2025 Mar 13.
The kinetics of molecular adsorption and desorption can unveil the details of the adsorption potential that impact, for instance, the overall sticking probability. This information is of particular importance for catalysis and gas sensing. We investigate the room-temperature CO adsorption on a model single-atom catalyst consisting of single Co atoms trapped in graphene (Gr) double carbon vacancies during Gr growth by chemical vapor deposition (CVD) on Ni(111). The study is conducted by combining a thermal desorption spectroscopy (TDS) instrument that allows the study of systems with a very low surface density of active sites, of the order of 10 monolayers (MLs) with variable-temperature scanning tunneling microscopy (VT-STM). Our findings show that CO adsorption onto the single Co atoms occurs mainly (up to 97%) through a reverse spillover mechanism, rather than through direct impingement from the gas phase. This mechanism involves CO physisorption and diffusion on pristine Gr, followed by lateral adsorption onto Co atoms. The reverse spillover channel effectively increases the sticking probability, by up to 2 orders of magnitude, compared with direct impingement. We use kinetic models to determine the relevant energies, such as the diffusion barrier for CO on Gr (68 ± 15 meV), the energy barrier for lateral CO adsorption on Co (174 ± 2 meV), and the chemisorption energy of CO on Co (0.97 ± 0.02 eV).
分子吸附和解吸的动力学可以揭示吸附势的细节，这些细节会影响例如整体的 sticking 概率。此信息对于催化和气体传感尤为重要。我们研究了室温下 CO 在一种模型单原子催化剂上的吸附情况，该催化剂由在化学气相沉积（CVD）生长石墨烯（Gr）于 Ni(111) 表面过程中被困在 Gr 双碳空位中的单个 Co 原子组成。该研究通过结合热脱附光谱（TDS）仪器和变温扫描隧道显微镜（VT-STM）进行，TDS 仪器可用于研究具有极低活性位点表面密度（约为 10 单层，即 10 MLs）的系统。我们的研究结果表明，CO 吸附到单个 Co 原子上主要（高达 97%）通过反向溢流机制发生，而不是通过气相的直接撞击。该机制涉及 CO 在原始 Gr 上的物理吸附和扩散，随后横向吸附到 Co 原子上。与直接撞击相比，反向溢流通道有效地将 sticking 概率提高了多达 2 个数量级。我们使用动力学模型来确定相关能量，例如 CO 在 Gr 上的扩散势垒（68 ± 15 meV）、CO 在 Co 上横向吸附的能垒（174 ± 2 meV）以及 CO 在 Co 上的化学吸附能（0.97 ± 0.02 eV）。
