Operando NMR Spectroscopic Analysis of the Effects of Pt Nanoparticle Size and Crystal Facet Structure on the Alcohol Reforming Reactions

The nanoparticle size and crystal facet structure of supported noble-metal photocatalysts are two critical factors affecting their activity and selectivity in alcohol reforming processes. Moreover, these effects are often intertwined and remain poorly understood at a fundamental level owing to the complexity of the reaction conditions at the solid-liquid interface. This is addressed in the present work by applying an operando 1H nuclear magnetic resonance spectroscopy method to investigate the detailed relationships between the nanoparticle size and facet structure of supported Pt graphitic carbon nitride photocatalysts and the selectivity and reaction rates of methanol and ethanol reforming products. The results demonstrate that relatively small Pt nanoparticles with no discernible Pt(111) crystal facets have high selectivity and efficiency for producing reforming products with a low degree of polymerization (e.g., aldehydes, hemiacetals, and acids), while relatively large nanoparticles with obvious Pt(111) crystal facets tend to produce reforming products with an increased degree of polymerization (e.g., acetals, ethers, and esters). The results clearly demonstrate that the degree of polymerization and the reforming pathways for methanol and ethanol molecules can be adjusted effectively by manipulating the size and crystal facets of the supported Pt nanoparticles, and these effects may be generally applicable to more complex alcohols of the form CH3(CH2)nOH (n > 1).