3 research outputs found
Tunable Photodeposition of MoS<sub>2</sub> onto a Composite of Reduced Graphene Oxide and CdS for Synergic Photocatalytic Hydrogen Generation
Recently,
MoS<sub>2</sub> as an excellent cocatalyst for hydrogen
evolution reaction (HER) has attracted extensive attention. In this
work, MoS<sub>2</sub> was controllably loaded on the composite of
reduced graphene oxide (rGO) and CdS (rGO/CdS) by a facile photoreduction
method at different pHs. At low pH 7, MoS<sub>2</sub> deposits on
the surface of the CdS particles of the composite. However, at high
pH 11, it loads on the exposed rGO. When MoS<sub>2</sub> is on the
rGO, the transfer of the photoexcited electron from CdS to rGO is
compatible with the HER at MoS<sub>2</sub> (synergic effect), whereas
the transfer is incompatible with the HER when it is on the CdS (antisynergic
effect). Moreover, the MoS<sub>2</sub> deposited on the CdS decreases
the photoabsorption and photoactivity of CdS, and the effect is avoided
when MoS<sub>2</sub> is on the rGO. The photocatalytic HER rate under
the synergic condition is 4.3 times as high as that under antisynergic
condition. This work would open a promising way to design and fabricate
the efficient composite photocatalysts
Facile Synthesis of Graphene Sponge from Graphene Oxide for Efficient Dye-Sensitized H<sub>2</sub> Evolution
Graphene is an advanced
carbon energy material due to its excellent properties. Reduction
of graphene oxide (GO) is the most promising mass production route
of graphene/reduced graphene oxide (rGO). To maintain graphene’s
properties and avoid restacking of rGO sheets in bulk, the preparation
of 3-dimensional porous graphene sponge via 2-dimensional rGO sheets
is considered as a good strategy. This article presents a facile route
to synthesize graphene sponge by thermal treating GO powder at low
temperature of 250 °C under N<sub>2</sub> atmosphere. The sponge
possesses macroporous structure (5–200 nm in size) with BET
specific surface area of 404 m<sup>2</sup> g<sup>–1</sup> and
high conductivity. The photocatalytic H<sub>2</sub> production activity
of the rGO sponge with a sensitizer Eosin Y (EY) and cocatalyst Pt
was investigated. The rGO sponge shows highly efficient dye-sensitized
photocatalytic H<sub>2</sub> evolution compared to that obtained via
a chemical reduction method. The maximum apparent quantum yield (AQY)
reaches up to 75.0% at 420 nm. The possible mechanisms are discussed.
The synthesis method can be expanded to prepare other graphene-based
materials
Facile Synthesis of Amorphous NiO/Reduced Graphene Oxide as a Cocatalyst for Enhanced Dye-Sensitized Photocatalytic H<sub>2</sub> Evolution
It is still a challenge to develop efficient catalysts
for hydrogen
evolution reaction (HER) via a low-cost and simple method. Herein,
we report an amorphous NiO/reduced graphene oxide (A-NG) composite
as a cocatalyst for enhanced photocatalytic H2 evolution
via dye sensitization. The A-NG composite is facilely fabricated by
calcinating the NiCl2/GO precursor at a low temperature
of 250 °C. The detailed characterizations show that amorphous
NiO presents as tiny nanoparticles highly dispersed on graphene sheets,
and nickel carbide is formed at the NiO/graphene interface, which
demonstrates the strong interaction between Ni and the defective carbon
of graphene. Compared with crystalline NiO/rGO (C-NG), the A-NG cocatalyst
shows much enhanced dye-sensitized photocatalytic HER activity because
the amorphous NiO nanoparticles can effectively adsorb the dye. As
a result, highly dispersed amorphous NiO accelerates the photoinduced
electron transfer from the excited dye to the cocatalyst, namely,
the amorphous nickel carbide formed between NiO and rGO. This work
provides a low-cost and simple method to develop efficient cocatalysts
for photocatalytic H2 evolution