3 research outputs found
Cobalt Molybdenum Nitride-Based Nanosheets for Seawater Splitting
The development of cost-effective bifunctional catalysts
for water
electrolysis is both a crucial necessity and an exciting scientific
challenge. Herein, a simple approach based on a metal–organic
framework sacrificial template to preparing cobalt molybdenum nitride
supported on nitrogen-doped carbon nanosheets is reported. The porous
structure of produced composite enables fast reaction kinetics, enhanced
stability, and high corrosion resistance in critical seawater conditions.
The cobalt molybdenum nitride-based electrocatalyst is tested toward
both oxygen evolution reaction and hydrogen evolution reaction half-reactions
using the seawater electrolyte, providing excellent performances that
are rationalized using density functional theory. Subsequently, the
nitride composite is tested as a bifunctional catalyst for the overall
splitting of KOH-treated seawater from the Mediterranean Sea. The
assembled system requires overpotentials of just 1.70 V to achieve
a current density of 100 mA cm–2 in 1 M KOH seawater
and continuously works for over 62 h. This work demonstrates the potential
of transition-metal nitrides for seawater splitting and represents
a step forward toward the cost-effective implementation of this technology
Enhanced Electrochemical Hydrogenation of Benzaldehyde to Benzyl Alcohol on Pd@Ni-MOF by Modifying the Adsorption Configuration
Electrocatalytic hydrogenation (ECH) approaches under
ambient temperature
and pressure offer significant potential advantages over thermal hydrogenation
processes but require highly active and efficient hydrogenation electrocatalysts.
The performance of such hydrogenation electrocatalysts strongly depends
not only on the active phase but also on the architecture and surface
chemistry of the support material. Herein, Pd nanoparticles supported
on a nickel metal–organic framework (MOF), Ni-MOF-74, are prepared,
and their activity toward the ECH of benzaldehyde (BZH) in a 3 M acetate
(pH 5.2) aqueous electrolyte is explored. An outstanding ECH rate
up to 283 μmol cm–2 h–1 with
a Faradaic efficiency (FE) of 76% is reached. Besides, higher FEs
of up to 96% are achieved using a step-function voltage. Materials
Studio and density functional theory calculations show these outstanding
performances to be associated with the Ni-MOF support that promotes
H-bond formation, facilitates water desorption, and induces favorable
tilted BZH adsorption on the surface of the Pd nanoparticles. In this
configuration, BZH is bonded to the Pd surface by the carbonyl group
rather than through the aromatic ring, thus reducing the energy barriers
of the elemental reaction steps and increasing the overall reaction
efficiency
Thermoelectric Performance of Surface-Engineered Cu<sub>1.5–<i>x</i></sub>Te–Cu<sub>2</sub>Se Nanocomposites
Cu2–xS and Cu2–xSe have recently been reported as
promising thermoelectric
(TE) materials for medium-temperature applications. In contrast, Cu2–xTe, another member of the copper
chalcogenide family, typically exhibits low Seebeck coefficients that
limit its potential to achieve a superior thermoelectric figure of
merit, zT, particularly in the low-temperature range
where this material could be effective. To address this, we investigated
the TE performance of Cu1.5–xTe–Cu2Se nanocomposites by consolidating surface-engineered Cu1.5Te nanocrystals. This surface engineering strategy allows
for precise adjustment of Cu/Te ratios and results in a reversible
phase transition at around 600 K in Cu1.5–xTe–Cu2Se nanocomposites, as systematically
confirmed by in situ high-temperature X-ray diffraction combined with
differential scanning calorimetry analysis. The phase transition leads
to a conversion from metallic-like to semiconducting-like TE properties.
Additionally, a layer of Cu2Se generated around Cu1.5–xTe nanoparticles effectively inhibits
Cu1.5–xTe grain growth, minimizing
thermal conductivity and decreasing hole concentration. These properties
indicate that copper telluride based compounds have a promising thermoelectric
potential, translated into a high dimensionless zT of 1.3 at 560 K