Confinement-Induced Indium Oxide Nanolayers Formed on Oxide Support for Enhanced CO₂ Hydrogenation Reaction

Abstract

An enclosed nanospace often shows a significant confinement effect on chemistry within its inner cavity, while whether an open space can have this effect remains elusive. Here, we show that the open surface of TiO₂ creates a confined environment for In₂O₃ which drives spontaneous transformation of free In₂O₃ nanoparticles in physical contact with TiO₂ nanoparticles into In oxide (InO_<i>x</i>) nanolayers covering onto the TiO₂ surface during CO₂ hydrogenation to CO. The formed InO_<i>x</i> nanolayers are easy to create surface oxygen vacancies but are against over-reduction to metallic In in the H₂-rich atmospheres, which thus show significantly enhanced activity and stability in comparison with the pure In₂O₃ catalyst. The formation of interfacial In-O-Ti bonding is identified to drive the In₂O₃ dispersion and stabilize the metastable InO_<i>x</i> layers. The InO_<i>x</i> overlayers with distinct chemistry from their free counterpart can be confined on various oxide surfaces, demonstrating the important confinement effect at oxide/oxide interfaces.