Engineering Peripheral Metal-Oxide Catalysis: Interparticle Spacing in Cu/ZrO2 Catalysts for Methanol Synthesis by CO2 Hydrogenation.

The periphery surrounding oxide-supported metal nanoparticles plays a crucial role in many catalytic reactions that exhibit strong metal-oxide promotional effects. Engineering this catalytically active periphery, where kinetically relevant surface intermediates are efficiently turned over, offers a pathway to optimized performance, yet it remains challenging due to the need for precise control over nanospatial catalyst features. Herein, we address this subject for the relevant case of methanol synthesis by CO2 hydrogenation on Cu/ZrO2 catalysts. The methanol synthesis rate reaches a maximum at a surface-to-surface Cu interparticle distance of ca. 15 nm. Operando modulation-excitation diffuse reflectance infrared spectroscopy reveals that this optimal spacing maximizes the fraction of surface-bound HCOO* intermediates, stabilized on coordinatively unsaturated Zr(IV) Lewis acid sites on the ZrO2 support, which are dynamically involved in catalysis. This particle spacing represents a shift in the reaction's kinetic control regime and the apparent activation energy for methanol synthesis. Engineering Cu interparticle spacing to the optimal value results in exceptionally high metal-specific methanol formation rates under industrially relevant reaction conditions. More broadly, our findings highlight that, beyond metal particle size, interparticle spacing is a key design parameter for catalyst systems featuring functional metal-oxide interfaces.