3 research outputs found
Large-Scale Synthesis of Graphene-Like MoSe<sub>2</sub> Nanosheets for Efficient Hydrogen Evolution Reaction
Two-dimensional
(2D) materials have attracted great attention by
researchers due to their fascinating properties and promising applications.
However, the synthesis methods for few layers are usually difficult
to expand to large area applications because of their low yield. In
this paper, graphene-like MoSe<sub>2</sub> nanosheets are successfully
and scaleable synthesized by a facile and low-cost hydrothermal method
under the synergy of PVP and graphene. The ultrathin MoSe<sub>2</sub> nanosheets are typically 1–3 layers, which are confirmed
by HRTEM. This unique structure makes this MoSe<sub>2</sub> electrode
material show superior activity toward the electrocatalytic hydrogen
production with a low Tafel slope about 70 mV·dec<sup>–1</sup>. Furthermore, the synthesized graphene-like MoSe<sub>2</sub> nanosheets
had a high stability during the electrocatalytic process and we nearly
cannot find the degradation after 1000 cyclic voltammetric sweeps
Oxygen Vacancy Promoted Heterogeneous Fenton-like Degradation of Ofloxacin at pH 3.2–9.0 by Cu Substituted Magnetic Fe<sub>3</sub>O<sub>4</sub>@FeOOH Nanocomposite
To develop an ultraefficient and
reusable heterogeneous Fenton-like
catalyst at a wide working pH range is a great challenge for its application
in practical water treatment. We report an oxygen vacancy promoted
heterogeneous Fenton-like reaction mechanism and an unprecedented
ofloxacin (OFX) degradation efficiency of Cu doped Fe<sub>3</sub>O<sub>4</sub>@FeOOH magnetic nanocomposite. Without the aid of external
energy, OFX was always completely removed within 30 min at pH 3.2–9.0.
Compared with Fe<sub>3</sub>O<sub>4</sub>@FeOOH, the pseudo-first-order
reaction constant was enhanced by 10 times due to Cu substitution
(9.04/h vs 0.94/h). Based on the X-ray photoelectron spectroscopy
(XPS), Raman analysis, and the investigation of H<sub>2</sub>O<sub>2</sub> decomposition, <sup>•</sup>OH generation, pH effect
on OFX removal and H<sub>2</sub>O<sub>2</sub> utilization efficiency,
the new formed oxygen vacancy from in situ Fe substitution by Cu rather
than promoted Fe<sup>3+</sup>/Fe<sup>2+</sup> cycle was responsible
for the ultraefficiency of Cu doped Fe<sub>3</sub>O<sub>4</sub>@FeOOH
at neutral and even alkaline pHs. Moreover, the catalyst had an excellent
long-term stability and could be easily recovered by magnetic separation,
which would not cause secondary pollution to treated water
Surface Facet of CuFeO<sub>2</sub> Nanocatalyst: A Key Parameter for H<sub>2</sub>O<sub>2</sub> Activation in Fenton-Like Reaction and Organic Pollutant Degradation
The
development of efficient heterogeneous Fenton catalysts is
mainly by “trial-and-error” concept and the factor determining
H<sub>2</sub>O<sub>2</sub> activation remains elusive. In this work,
we demonstrate that suitable facet exposure to elongate O–O
bond in H<sub>2</sub>O<sub>2</sub> is the key parameter determining
the Fenton catalyst’s activity. CuFeO<sub>2</sub> nanocubes
and nanoplates with different surface facets of {110} and {012} are
used to compare the effect of exposed facets on Fenton activity. The
results indicate that ofloxacin (OFX) degradation rate by CuFeO<sub>2</sub> {012} is four times faster than that of CuFeO<sub>2</sub> {110} (0.0408 vs 0.0101 min<sup>–1</sup>). In CuFeO<sub>2</sub> {012}-H<sub>2</sub>O<sub>2</sub> system, OFX is completely removed
at a pH range 3.2–10.1. The experimental results and theoretical
simulations show that <sup>•</sup>OH is preferentially formed
from the reduction of absorbed H<sub>2</sub>O<sub>2</sub> by electron
from CuFeO<sub>2</sub> {012} due to suitable elongation of O–O
(1.472 Å) bond length in H<sub>2</sub>O<sub>2</sub>. By contrast,
the O–O bond length is elongated from 1.468 to 3.290 Å
by CuFeO<sub>2</sub> {110} facet, H<sub>2</sub>O<sub>2</sub> tends
to be dissociated into −OH group and passivates {110} facet.
Besides, the new formed ≡Fe<sup>2+</sup>* on CuFeO<sub>2</sub> {012} facet can accelerate the redox cycle of Cu and Fe species,
leading to excellent long-term stability of CuFeO<sub>2</sub> nanoplates