Confining ultrafine Pt nanoparticles on In2O3 nanotubes for enhanced selective methanol production by CO2 hydrogenation

Abstract

A novel Pt@In₂O₃ catalyst assembled from ultrafine Pt nanoparticles confined on In₂O₃ nanotubes is fabricated from in situ topological transformation of H₂PtCl₆-soaked In-MIL-68 in an air atmosphere, which exhibits high performance for methanol production by CO₂ hydrogenation. The Pt@In₂O₃ catalyst is revealed to exhibit a strong confinement effect to stabilize the interaction between Pt and In₂O₃, affording improvements in methanol production, selectivity, and stability, compared with bare In₂O₃ nanotubes and the Pt/In₂O₃ catalyst made by directly loading Pt species on In₂O₃ nanotubes. The optimal Pt@In₂O₃ catalyst shows a high methanol yield of 29.0 mmol g⁻¹ h⁻¹ and a selectivity of 73% at 260 °C, together with a catalytic turnover number (TON) of 4128 based on the Pt species. Such a methanol production activity is about 2 times that of the commercial Cu/ZnO/Al₂O₃ catalyst and surpasses that of state-of-the-art In₂O₃-supported catalysts. Diverse techniques including aberration-corrected scanning transmission electron microscopy (AC-STEM), temperature-programmed desorption (TPD) of H₂ and CO₂, and in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) are used to demonstrate the crucial confinement effect of the In₂O₃ substrate on the Pt species for promoting the CO₂-to-methanol conversion. This work may motivate the employment of MOFs to pre-anchor metal precursors for the on site construction of supported catalysts with intimate contact and tailorable compositions for high-efficiency CO₂ conversion reactions.