posted on 2018-03-14, 00:00authored byShaopeng Rong, Pengyi Zhang, Fang Liu, Yajie Yang
The activity of exposed crystal facets
directly determines its
physicochemical properties. Thus, acquiring a high percentage of reactive
facets by crystal facet engineering is highly desirable for improving
the catalytic reactivity. Herein, single-crystalline α-MnO2 nanowires with major exposed high-index {310} facets were
synthesized via a facile hydrothermal route with the assistance of
a capping agent of oxalate ions. Comparing with two other low-index
facets ({100} and {110}), the resulting α-MnO2 nanowires
with exposed {310} facets exhibited much better activity and stability
for carcinogenic formaldehyde (HCHO) oxidation, making 100% of 100
ppm of HCHO mineralize into CO2 at 60 °C, even better
than some Ag supported catalysts. The density functional theory (DFT)
calculations were used to investigate the difference in the catalytic
activity of α-MnO2 with exposed {100}, {110}, and
{310} facets. The experimental characterization and theoretical calculations
all confirm that the {310} facets with high surface energy can not
only facilitate adsorption/activation of O2 and H2O but also be beneficial to the generation of oxygen vacancies, which
result in significantly enhanced activity for HCHO oxidation. This
is a valuable report on engineering surface facets in the preparation
of α-MnO2 as highly efficient oxidation catalysts.
This study deepens the understanding of facet-dependent activity of
α-MnO2 and points out a strategy to improve their
catalytic activity by crystal facet engineering.