The design of efficient semiconductor photocatalysts to promote solar-to-chemical conversion remains a tremendous challenge. The present study addresses this issue by loading Ag¬9(H2MSA)7 and Ag32(MPG)19 nanoclusters (NCs) onto graphitic carbon...
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)
n
OH (n >
1).
The
development of an efficient and durable photocatalyst is the
key to the degradation of tetracycline (TC). However, the ability
to monitor the concentration of TC accurately remains a significant
challenge. The present work addresses this issue by applying an operando 1H NMR spectroscopy technology for monitoring the TC concentration
using TiO2 photocatalysts with different oxygen vacancy
concentrations. The application of operando NMR spectra compensates
for the experimental error inherent in UV–vis spectrophotometry
analyses caused by the destruction of the chromogenic group and thereby
can accurately reflect the true degree of degradation. The TC degradation
performances of the photocatalysts are evaluated systematically, and
the obtained benzene ring concentrations are observed to contrast
sharply with the corresponding TC concentration results obtained by
UV–vis spectrophotometry. This research increases the availability,
reliability, and accuracy of the test methods employed in TC degradation
research and provides an experimental reference for the design of
high-efficiency catalysts.
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