5 research outputs found
Reduced Graphene Oxide/O-MWCNT Hybrids Functionalized with p‑Phenylenediamine as High-Performance MoS<sub>2</sub> Electrocatalyst Support for Hydrogen Evolution Reaction
Efficient hydrogen evolution through
water splitting at low overpotentials
is crucial to develop renewable energy technology, which depends on
the design of efficient and durable electrocatalysts composed of earth-abundant
elements. Herein, a highly and stable electrocatalyst for hydrogen
evolution reaction (HER) has been developed on the basis of MoS<sub>2</sub> on p-phenylenediamine (PPD)-functionalized reduced graphene
oxide/O-containing carbon nanotubes (rGO/O-MWCNT) hybrids via facile
and green hydrothermal process. Among the prepared catalysts, the
optimized MoS<sub>2</sub>/rGO/PPD/O-MWCNT with nanosized and highly
dispersed MoS<sub>2</sub> sheets provides a large amount of available
edge sites and the improved electron transfer in 3D conductive networks.
It exhibits excellent HER activity with a low overpotential of 90
mV and large current density of 47.6 mA·cm<sup>–2</sup> at 200 mV, as well as excellent stability in an acidic medium. The
Tafel slope of 48 mV·dec<sup>–1</sup> reveals the Volmer–Heyrovsky
mechanism for HER. Thus, this work paves a potential pathway for designing
efficient MoS<sub>2</sub>-based electrocatalysts for HER by functionalized
conductive substrates
Co-Doped MoS<sub>2</sub> Nanosheets with the Dominant CoMoS Phase Coated on Carbon as an Excellent Electrocatalyst for Hydrogen Evolution
Highly
active and low-cost catalysts for hydrogen evolution reaction
(HER) are crucial for the development of efficient water splitting.
Molybdenum disulfide (MoS<sub>2</sub>) nanosheets possess unique physical
and chemical properties, which make them promising candidates for
HER. Herein, we reported a facile, effective, and scalable strategy
by a deposition–precipitation method to fabricate metal-doped
(Fe, Co, Ni) molybdenum sulfide with a few layers on carbon black
as noble metal–free electrocatalysts for HER. The CoMoS phase
after thermal annealing in Co-doped MoS<sub>2</sub> plays a crucial
role for the enhanced HER. The optimized Co-doped MoS<sub>2</sub> catalyst
shows superior HER performance with a high exchange current density
of 0.03 mA·cm<sup>–2</sup>, low onset potential of 90
mV, and small Tafel slope of 50 mV·dec<sup>–1</sup>, which
also exhibits excellent stability of 10000 cycles with negligible
loss of the cathodic current. The superior HER activity originates
from the synergistically structural and electronic modulations between
MoS<sub>2</sub> and Co ions, abundant defects in the active edge sites,
as well as the good balance between active sites and electronic conductivity.
Thanks to their ease of synthesis, low cost, and high activity, the
Co-doped MoS<sub>2</sub> catalysts appear to be promising HER catalysts
for electrochemical water splitting
Molybdenum Polysulfide Anchored on Porous Zr-Metal Organic Framework To Enhance the Performance of Hydrogen Evolution Reaction
Replacement of precious
platinum with efficient and low-cost catalysts
for electrocatalytic hydrogen evolution reaction (HER) at low overpotentials
holds tremendous promise for clean energy devices. Herein, molybdenum
polysulfide (MoS<sub><i>x</i></sub>) anchored on a porous
Zr-metal organic framework (Zr-MOF, UiO-66-NH<sub>2</sub>) by chemical
interactions is fabricated by a facile and one-pot solvothermal method
for HER application. The distinctive design of the Zr-MOF stabilized
MoS<sub><i>x</i></sub> composite enables remarkable electrochemical
HER activity with a Tafel slope of 59 mV·dec<sup>–1</sup>, a lower onset potential of nearly 125 mV, and a cathode current
of 10 mA·cm<sup>–2</sup> at an overpotential of 200 mV,
which also exhibits excellent durability in an acid medium. The superior
HER performance should ascribe to the fast electron transport from
the less conducting MoS<sub><i>x</i></sub> nanosheets to
the electrode, high effective surface area, and number of active sites,
as well as the favorable delivery for local protons in the porous
Zr-MOF structure during the electrocatalytic reaction. Thus, this
work paves a potential pathway for designing efficient Mo-based HER
electrocatalysts by the combination of molybdenum polysulfide and
versatile proton-conductive MOFs
Strongly Coupled FeNi Alloys/NiFe<sub>2</sub>O<sub>4</sub>@Carbonitride Layers-Assembled Microboxes for Enhanced Oxygen Evolution Reaction
Hydrogen
produced from electrocatalytic water splitting is a promising route
due to the sustainable powers derived from the solar and wind energy.
However, the sluggish kinetics at the anode for water splitting makes
the highly effective and inexpensive electrocatalysts desirable in
oxygen evolution reaction (OER) by structure and composition modulations.
Metal–organic frameworks (MOFs) have been intensively used
as the templates/precursors to synthesize complex hollow structures
for various energy-related applications. Herein, an effective and
facile template-engaged strategy originated from bimetal MOFs is developed
to construct hollow microcubes assembled by interconnected nanopolyhedron,
consisting of intimately dominant FeNi alloys coupled with a small
NiFe<sub>2</sub>O<sub>4</sub> oxide, which was confined within carbonitride
outer shell (denoted as FeNi/NiFe<sub>2</sub>O<sub>4</sub>@NC) via
one-step annealing treatment. The optimized FeNi/NiFe<sub>2</sub>O<sub>4</sub>@NC exhibits excellent electrocatalytic performances toward
OER in alkaline media, showing 10 mA·cm<sup>–2</sup> at
η = 316 mV, lower Tafel slope (60 mV·dec<sup>–1</sup>), and excellent durability without decay after 5000 CV cycles, which
also surpasses the IrO<sub>2</sub> catalyst and most of non-noble
catalysts in the OER, demonstrating a great perspective. The superior
OER performance is ascribed to the hollow interior for fast mass transport,
in situ formed strong coupling between FeNi alloys and NiFe<sub>2</sub>O<sub>4</sub> for electron transfer, and the protection of carbonitride
layers for long stability
Metallic Cobalt Encapsulated in Bamboo-Like and Nitrogen-Rich Carbonitride Nanotubes for Hydrogen Evolution Reaction
Despite being technically possible,
the hydrogen production by means of electrocatalytic water splitting
is still practically unreachable mainly because of the lack of inexpensive
and high active catalysts. Herein, a novel and facile approach by
melamine polymerization, exfoliation and Co<sup>2+</sup>-assisted
thermal annealing is developed to fabricate Co nanoparticles embedded
in bamboo-like and nitrogen-rich carbonitride nanotubes (Co@NCN).
The electronic interaction between the embedded Co nanoparticles and
N-rich carbonitride nanotubes could strongly promote the HER performance.
The optimized Co@NCN-800 exhibits outstanding HER activity with an
onset potential of −89 mV (vs RHE), a large exchange current
density of 62.2 μA cm<sup>–2</sup>, and small Tafel slope
of 82 mV dec<sup>–1</sup>, as well as excellent stability (5000
cycles) in acid media, demonstrating the potential for the replacement
of Pt-based catalysts. Control experiments reveal that the superior
performance should be ascribed to the synergistic effects between
embedded Co nanoparticles and N-rich carbonitride nanotubes, which
originate from the high pyridinic N content, fast charge transfer
rate from Co particles to electrodes via electronic coupling, and
porous and bamboo-like carbonitride nanotubes for more active sites
in HER