Imaging the ordering of a weakly adsorbed two-dimensional condensate: ambient-pressure microscopy and spectroscopy of CO2 molecules on rutile TiO2(110)

• Published in: Physical chemistry chemical physics : PCCP 2018, Vol.20 (19), p.13122-13126
• Main Authors: Hamlyn, Rebecca C E, Mahapatra, Mausumi, Grinter, David C, Xu, Fang, Luo, Si, Palomino, Robert M, Kattel, Shyam, Waluyo, Iradwikanari, Liu, Ping, Stacchiola, Dario J, Senanayake, Sanjaya D, Rodriguez, José A
• Format: Article
• Language: English
• Subjects: Bonding strength; Carbon dioxide; Chemical reactions; Greenhouse effect; Greenhouse gases; INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; MATERIALS SCIENCE; Microscopy; Organic chemistry; Rutile; Scanning tunneling microscopy; Soft X ray spectroscopy; Soft x rays; Spectrum analysis; Titanium dioxide; X ray photoelectron spectroscopy
• ISSN: 1463-9076; 1463-9084
• DOI: 10.1039/c8cp01614c

Disorder–Order transitions in a weakly adsorbed two-dimensional film have been identified for the first time using ambient-pressure scanning tunneling microscopy (AP-STM) and X-ray photoelectron spectroscopy (AP-XPS). As of late, great effort has been devoted to the capture, activation and conversion of carbon dioxide (CO2), a ubiquitous greenhouse gas and by-product of many chemical processes. The high stability and non-polar nature of CO2 leads to weak bonding with well-defined surfaces of metals and oxides. CO2 adsorbs molecularly on the rutile TiO2(110) surface with a low adsorption energy of ∼10 kcal mol−1. In spite of this weak binding, images of AP-STM show that a substantial amount of CO2 can reside on a TiO2(110) surface at room temperature forming two-dimensionally ordered films. We have employed microscopic imaging under in situ conditions, soft X-ray spectroscopy and theory to decipher the unique ordering behavior seen for CO2 on TiO2(110).