Eren Baran, Sole Christopher G, Lacasa Jesús S, Grinter David, Venturini Federica, Held Georg, Esconjauregui Cruz S, Weatherup Robert S
Department of Chemical and Biological Physics, Weizmann Institute of Science, 234 Herzl Street, 76100 Rehovot, Israel.
Phys Chem Chem Phys. 2020 Sep 14;22(34):18806-18814. doi: 10.1039/d0cp00347f. Epub 2020 Apr 3.
Methanol is a promising chemical for the safe and efficient storage of hydrogen, where methanol conversion reactions can generate a hydrogen-containing gas mixture. Understanding the chemical state of the catalyst over which these reactions occur and the interplay with the adsorbed species present is key to the design of improved catalysts and process conditions. Here we study polycrystalline Cu foils using ambient pressure X-ray spectroscopies to reveal the Cu oxidation state and identify the adsorbed species during partial oxidation (CHOH + O), steam reforming (CHOH + HO), and autothermal reforming (CHOH + O + HO) of methanol at 200 °C surface temperature and in the mbar pressure range. We find that the Cu surface remains highly metallic throughout partial oxidation and steam reforming reactions, even for oxygen-rich conditions. However, for autothermal reforming the Cu surface shows significant oxidation towards CuO. We rationalise this behaviour on the basis of the shift in equilibrium of the CHOH* + O* ⇌ CHO* + OH* reaction step caused by the addition of HO.
甲醇是一种用于安全高效储氢的有前景的化学品，甲醇转化反应可生成含氢气体混合物。了解这些反应所发生的催化剂的化学状态以及与存在的吸附物种之间的相互作用，是设计改进型催化剂和工艺条件的关键。在此，我们使用常压X射线光谱研究多晶铜箔，以揭示铜的氧化态，并确定在200°C表面温度和毫巴压力范围内甲醇的部分氧化（CH₃OH + O）、蒸汽重整（CH₃OH + H₂O）和自热重整（CH₃OH + O + H₂O）过程中的吸附物种。我们发现，即使在富氧条件下，在整个部分氧化和蒸汽重整反应过程中，铜表面仍保持高度金属性。然而，对于自热重整，铜表面显示出向CuO的显著氧化。我们基于添加H₂O导致的CH₃OH* + O* ⇌ CH₂O* + OH*反应步骤平衡的移动来解释这种行为。
