Confinement-Induced Indium Oxide Nanolayers Formed on Oxide Support for Enhanced CO₂ 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 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) nanolayers covering onto the TiO₂ surface during CO₂ hydrogenation to CO. The formed InO 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 layers. The InO overlayers with distinct chemistry from their free counterpart can be confined on various oxide surfaces, demonstrating the important confinement effect at oxide/oxide interfaces.