3 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
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