Qiu Chengwu, Odarchenko Yaroslav, Meng Qingwei, Xu Shaojun, Lezcano-Gonzalez Ines, Olalde-Velasco Paul, Maccherozzi Francesco, Zanetti-Domingues Laura, Martin-Fernandez Marisa, Beale Andrew M
Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, U.K.
Research Complex at Harwell (RCaH), Harwell, Didcot OX11 0FA, Oxfordshire, U.K.
ACS Catal. 2022 Aug 5;12(15):9125-9134. doi: 10.1021/acscatal.2c00611. Epub 2022 Jul 14.
Improving both the extent of metallic Co nanoparticle (Co NP) formation and their stability is necessary to ensure good catalytic performance, particularly for Fischer-Tropsch synthesis (FTS). Here, we observe how the presence of surface oxygen vacancies (O) on TiO can readily reduce individual CoO NPs directly into CoO/Co in the freshly prepared sample by using a combination of X-ray photoemission electron microscopy (X-PEEM) coupled with soft X-ray absorption spectroscopy. The O are particularly good at reducing the edge of the NPs as opposed to their center, leading to smaller particles being more reduced than larger ones. We then show how further reduction (and O consumption) is achieved during heating in H/syngas (H + CO) and reveal that O also prevents total reoxidation of Co NPs in syngas, particularly the smallest (∼8 nm) particles, thus maintaining the presence of metallic Co, potentially improving catalyst performance.
提高金属钴纳米颗粒（Co NP）的形成程度及其稳定性对于确保良好的催化性能至关重要，特别是对于费托合成（FTS）而言。在此，我们通过结合X射线光电子发射显微镜（X-PEEM）与软X射线吸收光谱，观察了TiO表面氧空位（O）的存在如何在新制备的样品中将单个CoO NPs直接还原为CoO/Co。与NP的中心相比，O特别擅长还原NP的边缘，导致较小的颗粒比较大的颗粒还原程度更高。然后我们展示了在H/合成气（H + CO）中加热期间如何实现进一步还原（以及O消耗），并揭示O还可防止合成气中Co NPs的完全再氧化，特别是最小的（约8 nm）颗粒，从而维持金属Co的存在，有可能提高催化剂性能。
