3 research outputs found
Quantitative Study of Charge Carrier Dynamics in Well-Defined WO<sub>3</sub> Nanowires and Nanosheets: Insight into the Crystal Facet Effect in Photocatalysis
Photocatalysts
with different morphologies and specific exposed
facets usually exhibit distinguished activities. Previous researches
have focused on revealing the essence of the facet effect in photocatalysis;
however, quantitative analyses on the differences of carrier dynamic
between different facets are scarce. Herein, we successfully synthesized
WO<sub>3</sub> nanosheets and nanowires with dominant exposed facets
of {001} and {110}, respectively. The lower hole effective mass on
{110} (0.94<i>m</i><sub>0</sub>) than on {001} (1.28<i>m</i><sub>0</sub>) calculated by density functional theory leads
to the higher hole mobility on {110} (4.92 cm<sup>2</sup> V<sup>–1</sup> s<sup>–1</sup>) than on {001} (3.14 cm<sup>2</sup> V<sup>–1</sup> s<sup>–1</sup>). Combined with the Einstein
equation and the lifetime of the hole, the calculated hole diffusion
length on {110} (74.8 nm) is larger than on {001} (53.4 nm). Overall,
the lower hole effective mass, higher hole mobility, and greater hole
diffusion length on {110} collectively result in a photocatalytic
activity on benzyl alcohol oxidation 2.46 times as high as that on
{001}
Metal (Hydr)oxides@Polymer Core–Shell Strategy to Metal Single-Atom Materials
Preparing
metal single-atom materials is currently attracting tremendous
attention and remains a significant challenge. Herein, we report a
novel core–shell strategy to synthesize single-atom materials.
In this strategy, metal hydroxides or oxides are coated with polymers,
followed by high-temperature pyrolysis and acid leaching, metal single
atoms are anchored on the inner wall of hollow nitrogen-doped carbon
(CN) materials. By changing metal precursors or polymers, we demonstrate
the successful synthesis of different metal single atoms dispersed
on CN materials (SA-M/CN, M = Fe, Co, Ni, Mn, FeCo, FeNi, etc.). Interestingly,
the obtained SA-Fe/CN exhibits much higher catalytic activity for
hydroxylation of benzene to phenol than Fe nanoparticles/CN (45% vs
5% benzene conversion). First-principle calculations further reveal
that the high reactivity originates from the easier formation of activated
oxygen species at the single Fe site. Our methodology provides a convenient
route to prepare a variety of metal single-atom materials representing
a new class of catalysts
Low-Temperature Solution-Processed Tin Oxide as an Alternative Electron Transporting Layer for Efficient Perovskite Solar Cells
Lead
halide perovskite solar cells with the high efficiencies typically
use high-temperature processed TiO<sub>2</sub> as the electron transporting
layers (ETLs). Here, we demonstrate that low-temperature solution-processed
nanocrystalline SnO<sub>2</sub> can be an excellent alternative ETL
material for efficient perovskite solar cells. Our best-performing
planar cell using such a SnO<sub>2</sub> ETL has achieved an average
efficiency of 16.02%, obtained from efficiencies measured from both
reverse and forward voltage scans. The outstanding performance of
SnO<sub>2</sub> ETLs is attributed to the excellent properties of
nanocrystalline SnO<sub>2</sub> films, such as good antireflection,
suitable band edge positions, and high electron mobility. The simple
low-temperature process is compatible with the roll-to-roll manufacturing
of low-cost perovskite solar cells on flexible substrates