7 research outputs found
Preserving Cu<sup>+</sup> Active Sites through Intensified Electron Density for Sustained CO<sub>2</sub> Electroreduction
In the realm of CO2 electroreduction to C2 fuels and feedstocks, copper-based oxides (CuOx) stand out for their exceptional ability to adsorb
*CO intermediates.
A significant challenge in the use of Cu-based oxide catalysts is
the electroreduction-driven transformation of Cu+ species
to metallic Cu, predominantly attributed to the direct electron-mediated
disruption of Cu–O bonds. Addressing this, our study introduces
an approach that enhances the electron density in Cu2O
through the integration of MoS2, thereby stabilizing the
Cu+ species. This method mitigates the Cu–O bond
attack by dispersing the excess electrons, which originate from the
external electrode, within the Cu2O. Our composite material,
Cu2O-MoS2, demonstrates a 1.9-fold increase
in Faraday efficiency for C2H4 production (FEC2H4), achieving 23.3% at −1.3 V vs RHE, and exhibits
predominant Cu+ stability compared to pure Cu2O. Both experimental and computational analyses reveal that the lower
work function (WF) of MoS2, relative to Cu2O,
facilitates electron transfer from MoS2 to Cu2O, consequently augmenting the electron density in Cu2O. This increased electron density provides a protective barrier
against electron attacks from the external electrode on the Cu–O
bond. Our findings present a strategy for enhancing Cu+ stability, thereby promoting C2H4 production.
Furthermore, this research contributes a different insight into the
design of selective and stable catalysts for CO2 reduction
La<sub>2</sub>O<sub>3</sub> Doped Carbonaceous Microspheres: A Novel Bifunctional Electrocatalyst for Oxygen Reduction and Evolution Reactions with Ultrahigh Mass Activity
An efficient and robust bifunctional
electrocatalyst for both ORR
and OER is highly desired for the applications in renewable energy
technologies. Here, we prepare the carbonaceous microspheres (CMSs)
by a facile hydrothermal treatment of glucose precursor and then dope
the CMSs with La<sub>2</sub>O<sub>3</sub>, resulting in a high performance
bifunctional electrocatalyst of La<sub>2</sub>O<sub>3</sub>@CMSs.
In alkaline solution, the La<sub>2</sub>O<sub>3</sub>@CMSs catalyzes
oxygen reduction reactions (ORR) with an onset potential of 0.80 V
versus RHE and an overpotential only of 600 mV to achieve a current
density of 1.3 mA cm<sup>–2</sup>. Meanwhile, oxygen evolution
reaction (OER) at La<sub>2</sub>O<sub>3</sub>@CMSs electrode occurs
at an onset potential of 1.60 V versus RHE and the overpotential is
only 370 mV. Also, the as-prepared La<sub>2</sub>O<sub>3</sub>@CMSs
exhibits high Faraday efficiency and long-term stability toward ORR
and OER. Significantly, we demonstrate that La<sub>2</sub>O<sub>3</sub>@CMSs possesses surprisingly high mass activity, which is calculated
to be 78.4 A g<sup>–1</sup> for ORR and 831.5 A g<sup>–1</sup> for OER, respectively. A potential window for ORR and OER at the
modified electrode is estimated to be 0.80 V, implying a promising
bifunctional electrocatalytical performance of La<sub>2</sub>O<sub>3</sub>@CMSs. The improvement of the bifunctional electrocatalytical
activity may be due to the generation of active component of La–O
and C–O at the surface and its synergistic interact with the
La<sub>2</sub>O<sub>3</sub>@CMSs. This work not only provides a facile
strategy for preparing highly efficient bifunctional electrocatalyst,
but also offers an insight into the design of metal-oxides doped carbon
materials for energy storage and conversion applications
Controllable Growth of CNTs on Graphene as High-Performance Electrode Material for Supercapacitors
Design and synthesis of three-dimensional
(3D) structured carbon materials are crucial for achieving high-performance
supercapacitors (SC) for energy storage. Here, we report the preparation
of 3D architectured GN-CNT hybrid as SC electrodes. Controllable growth
of carbon nanotubes on graphene sheets was realized through a facile
one-pot pyrolysis strategy. The length of the carbon nanotubes could
be rationally tuned by adjusting the amount of precursors. Correspondingly,
the resulted GN-CNT hybrid showed adjustable electrochemical performance
as an SC electrode. Importantly, the GN-CNT exhibited a high specific
surface area of 903 m<sup>2</sup> g<sup>–1</sup> and maximum
specific capacitance of 413 F g<sup>–1</sup> as SC electrodes
at a scan rate of 5 mV s<sup>–1</sup> in 6 M KOH aqueous solution.
This work paves a feasible pathway to prepare carbon electrode materials
with favorable 3D architecture and high performance, for use in energy
storage and conversion
Built-in Electric Field-Induced Work Function Reduction in C–Co<sub>3</sub>O<sub>4</sub> for Efficient Electrochemical Nitrogen Reduction
Co3O4 is a highly selective catalyst
for
the electrochemical conversion of N2 to NH3.
However, the large work function (WF) of Co3O4 leads to unsatisfactory activity. To address this issue, a strong
built-in electric field (BIEF) was constructed in Co3O4 by doping C atoms (C–Co3O4)
to reduce the WF for improving the electrocatalytic performance. C–Co3O4 exhibited a remarkable NH3 yield
of 38.5 μg h–1 mgcat–1 and a promoted FE of 15.1% at −0.3 V vs RHE, which were 2.2
and 1.9 times higher than those of pure Co3O4, respectively. Kelvin probe force microscopy (KPFM), zeta potential,
and ultraviolet photoelectron spectrometry (UPS) confirmed the formation
of strong BIEF and WF reduction in C–Co3O4. Additionally, in situ Raman measurements and density functional
theory (DFT) calculations revealed the relationship between BIEF and
WF and provided insights into the reaction mechanism. Our work offers
valuable guidance for the design and development of more efficient
nitrogen reduction catalysts
Deciphering the Stability Mechanism of Cu Active Sites in CO<sub>2</sub> Electroreduction via Suppression of Antibonding Orbital Occupancy in the O 2p-Cu 3d Hybridization
Copper-based catalysts, hallmarked by their ideal C–C
coupling
energy facilitated by the symbiotic presence of Cu+ and
Cu0 active sites, are poised to revolutionize the selective
electrochemical reduction of CO2 to C2H4. Regrettably, these catalysts are beleaguered by the unavoidable
diminution of Cu+ to Cu0 during the reaction
process, resulting in suboptimal C2H4 yields.
To circumvent this limitation, we have judiciously mitigated the antibonding
orbital occupancy in the O 2p and Cu+ 3d hybridization
by introducing Cu defects into Cu2O, thereby augmenting
the Cu–O bond strength to stabilize Cu+ sites and
further decipher the stabilization mechanism of Cu+. This
structural refinement, illuminated by meticulous DFT calculations,
fosters a heightened free energy threshold for the hydrogen evolution
reaction (HER), while orchestrating a thermodynamically favorable
milieu for enhanced C–C coupling within the Cu-deficient Cu2O (Cuv-Cu2O). Empirically, Cuv-Cu2O has outperformed its pure Cu2O counterpart,
exhibiting a prominent C2H4/CO ratio of 1.69
as opposed to 1.01, without conceding significant ground in C2H4 production over an 8 h span at −1.3 V
vs RHE. This endeavor not only delineates the critical influence of
antibonding orbital occupancy on bond strength and reveals the deep
mechanism about Cu+ sites but also charts a pioneering
pathway in the realm of advanced materials design
Cu<sub>2</sub>O Decorated with Cocatalyst MoS<sub>2</sub> for Solar Hydrogen Production with Enhanced Efficiency under Visible Light
In this work, we have prepared a <i>p</i>-type semiconductor
of Cu<sub>2</sub>O decorated with MoS<sub>2</sub> nanosheets as cocatalyst
for efficient solar hydrogen production under visible light. Results
show that Cu<sub>2</sub>O decorated with 1.0 wt % MoS<sub>2</sub> presents
the maximum reduction photocurrent density of 0.17 mA cm<sup>–2</sup>, which is 7-fold higher than pristine Cu<sub>2</sub>O. Furthermore,
the as-prepared MoS<sub>2</sub>@Cu<sub>2</sub>O exhibits remarkable
photostability with only 7% loss of its original photocurrent after
9 h of continuous work. The excellent performance of MoS<sub>2</sub>@Cu<sub>2</sub>O is ascribed to the introduction of active sites
of MoS<sub>2</sub> nanosheets as cocatalyst to the surface of Cu<sub>2</sub>O nanoparticles, which activates the photocatalyst by lowering
the electrochemical proton reduction overpotential and also inhibits
photoinduced corrosion during the measurement
Cu-Modified Palladium Catalysts: Boosting Formate Electrooxidation via Interfacially OH<sub>ad</sub>-Driven H<sub>ad</sub> Removal
Direct formate fuel cells have gained traction due to
their eco-friendly
credentials and inherent safety. However, their potential is hampered
by the kinetic challenges of the formate oxidation reaction (FOR)
on Pd-based catalysts, chiefly due to the unfavorable adsorption of
hydrogen species (Had). These species clog the active sites,
hindering efficient catalysis. Here, we introduce a straightforward
strategy to remedy this bottleneck by incorporating Pd with Cu to
expedite the removal of Pd–Had in alkaline media.
Notably, Cu plays a pivotal role in bolstering the concentration of
hydroxyl adsorbates (OHad) on the surface of catalyst.
These OHad species can react with Had, effectively
unblocking the active sites for FOR. The as-synthesized catalyst of
PdCu/C exhibits a superior FOR performance, boasting a remarkable
mass activity of 3.62 A mg–1. Through CO-stripping
voltammetry, we discern that the presence of Cu in Pd markedly speeds
up the formation of adsorbed hydroxyl species (OHad) at
diminished potentials. This, in turn, aids the oxidative removal of
Pd–Had, leveraging a synergistic mechanism during
FOR. Density functional theory computations further reveal intensified
interactions between adsorbed oxygen species and intermediates, underscoring
that the Cu–Pd interface exhibits greater oxyphilicity compared
to pristine Pd. In this study, we present both experimental and theoretical
corroborations, unequivocally highlighting that the integrated copper
species markedly amplify the generation of OHad, ensuring
efficient removal of Had. This work paves the way, shedding
light on the strategic design of high-performing FOR catalysts