Operando X-ray Absorption Spectroscopic Study of Ultradispersed Mo/TiO 2 CO 2 -Hydrogenation Catalysts: Why Does Rutile Promote Methanol Synthesis?

• Published in: ACS catalysis 2023-11, Vol.13 (21), p.13982-13993
• Main Authors: Len, T., Afanasiev, P., Yan, Y., Aouine, M., Morfin, F., Piccolo, L.
• Format: Article
• Language: English
• Subjects: Catalysis; Chemical Sciences
• ISSN: 2155-5435; 2155-5435
• DOI: 10.1021/acscatal.3c02149

CO2 hydrogenation to methanol is an important process for an ecologic and energetic shift, which stimulates the development of active catalysts based on non-critical elements. We have recently reported that Mo atoms anchored on rutile titania nanorods exhibit distinctive performance in methanol synthesis, i.e. higher activity and methanol selectivity than Mo dispersed on anatase and P25 commercial forms. In this work, for deciphering the origin of the higher performance of rutile, this support is compared to other selected oxides of interest, and Mo/TiO2 catalysts are investigated operando at high pressure by synchrotron X-ray absorption spectroscopy at the Mo K edge combined with chemometric treatments. The main structural change occurs during the reductive activation pretreatment, when MoVI species convert to more reduced ones. However, while on anatase titania the active species are mostly MoO2-like clusters, on rutile titania single Mo atoms are not only more present but may also replace surface Ti atoms, which would explain the more stable single-atomic dispersion and the rutile-like coordination of Mo, as well as the low sensitivity of the latter to the chemical environment and the metal loading. As a result, Mo-doped rutile titania acts as a promising atomically dispersed catalyst for CO2 hydrogenation to methanol.