Reaction-induced surface/subsurface indium species formation on ZrO₂ for enhanced CO₂ hydrogenation to methanol

The complex structural evolution of oxide catalysts during CO₂ hydrogenation presents both challenges and opportunities for optimizing catalytic performance. This study demonstrates reaction-induced transformation of In₂O₃ particles into InO_x nanolayers and subsurface In-Zr-O solid solutions on ZrO₂ (denoted as In-ZrO₂@InO_x), significantly enhancing methanol synthesis efficiency. Under CO₂/H₂ reaction conditions, mobile metallic In⁰ generated from H₂ reduction drives redispersion of In₂O₃ into surface InO_x nanolayers, while subsequent inter-diffusion between In⁰ and Zr(CO₃)₂ leads to the formation of subsurface In-Zr-O solid solutions. Through precise control of temperature, pressure, and gas composition, we achieve optimal distribution of three distinct In species: In₂O₃ nanoparticles, surface InO_x nanolayers, and subsurface In-Zr-O solid solutions. The engineered In-ZrO₂@InO_x catalyst exhibits a methanol space-time yield of 1.1 g_methanol/g_cat/h with remarkable stability over 600 hours at 300 °C. Our findings highlight the crucial role of both surface and subsurface oxide species in oxide-catalyzed reactions and demonstrate the effectiveness of reaction-driven restructuring strategies for catalyst optimization.