Confinement-Induced Indium Oxide Nanolayers Formed on Oxide Support for Enhanced CO 2 Hydrogenation Reaction.

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 TiO 2 creates a confined environment for In 2 O 3 which drives spontaneous transformation of free In 2 O 3 nanoparticles in physical contact with TiO 2 nanoparticles into In oxide (InO x ) nanolayers covering onto the TiO 2 surface during CO 2 hydrogenation to CO. The formed InO x nanolayers are easy to create surface oxygen vacancies but are against over-reduction to metallic In in the H 2 -rich atmospheres, which thus show significantly enhanced activity and stability in comparison with the pure In 2 O 3 catalyst. The formation of interfacial In-O-Ti bonding is identified to drive the In 2 O 3 dispersion and stabilize the metastable InO x layers. The InO x overlayers with distinct chemistry from their free counterpart can be confined on various oxide surfaces, demonstrating the important confinement effect at oxide/oxide interfaces.