Electronic coupling of lattice-stabilized Co with ZrO2 promotes In2O3 catalysts for CO2 hydrogenation to methanol

Cobalt is a promising earth-abundant promoter for In 2 O 3 -based CO 2 hydrogenation catalysts, yet its optimal integration and function within ZrO 2 -supported ternary systems remain poorly understood. Here, we show that incorporation into the ZrO 2 lattice converts Co from a restructuring-prone surface modifier into a redox-active promoter for In 2 O 3 . Using a state-of-the-art In 2 O 3 /m-ZrO 2 composition as the parent formulation, cobalt was either incorporated into the ZrO 2 lattice by hydrothermal doping (In 2 O 3 /mZrO 2 -Co) or co-deposited with the indium precursor on the support surface by impregnation (Co-In 2 O 3 /mZrO 2 ). Hydrothermal doping stabilizes cobalt as atomically dispersed species strongly coupled to ZrO 2 , enabling reversible Co 3+ /Co 2+ redox cycling, enhancing oxygen-deficient site formation, and preventing the Co-In restructuring observed for surface-deposited cobalt under CO 2 hydrogenation conditions. Kinetic evaluation, 200 h stability testing, and extensive in situ characterization establish that lattice-stabilized cobalt promotes CO 2 adsorption, H 2 activation, and intermediate hydrogenations, while suppressing detrimental catalyst evolution. Consequently, lattice-stabilized cobalt increases methanol space-time yield by up to 1.7-fold, reaching among the highest indium-specific methanol productivities reported for non-precious-metal-promoted systems.