Designing and synthesizing a highly active single atom
catalyst,
especially monodispersed noble-metal atoms fixed in two-dimensional
layered double hydroxide (LDH) nanostructures, is crucial in accelerating
the slow oxygen evolution reaction (OER). Here, Ru single atoms (SAs)
are stabilized on NiFe LDH (SARu/NiFe LDH) via an oxygen-coordinated bond after a facile solution reduction procedure.
The OER activity evaluation at similar mass loading on glassy carbon
reveals that SARu/NiFe LDH shows more activity than pure
NiFe LDH in basic media, possessing 99.3% of Faradaic efficiency based
on rotating ring-disk electrode measurement. This is mainly due to
a strong synergy between Ru SAs and NiFe LDH support. Furthermore,
these supported catalysts are developed to an integrative 3D electrode in situ of the nickel foam with a higher specific surface
area, which needs only an ultralow overpotential of 196 mV at 10 mA
cm–2. This is one of the most efficient electrode
containing monoatomic components to date. Theoretical calculations
suggests that active sites of Ru can facilitate the rearrangement
of electrons and optimize the binding energy both SARu/NiFe
LDH catalyst and intermediates during the OER, thereby improving the
intrinsic OER activity. This study provides a general avenue to developing
efficiently monoatomic and even multiatomic catalysts in the future.
Improving the intrinsic catalytic activity of NiFe layered double hydroxide (LDH), which is a benchmark electrocatalyst for oxygen evolution reaction (OER), is a significant challenge. In the present study, we doped ruthenium ions into NiFe LDH (Ru-NiFe LDH) to accelerate the OER kinetics. Electrochemical measurements of NiFe LDH and Ru-NiFe LDH at similar mass loadings showed that Ru-NiFe LDH demonstrated a higher OER activity than that of NiFe LDH. Ru-NiFe LDH only requires an overpotential of 246 mV at 10 mA cm-2 in alkaline media. This is attributed to ruthenium doping primarily, which can promote the catalytic activity of Fe sites and boost the electronic interaction among the Ni, Fe, and Ru metals according to the theoretical calculations. Ru-NiFe LDH is stable during OER stability measurements, which was confirmed by structure and elemental analysis. These findings will provide a useful approach for promoting the intrinsic activity of multi-metallic (oxy) hydroxide electrocatalysts toward the OER.
The furanic diether of 2,5-bis(isopropoxymethyl)furan (BPMF) derived from 5-hydroxymethylfurfural (HMF) can be used as a biobased fuel or fuel additive. It is highly desirable but challenging to develop a one-pot process for the transformation of HMF into BPMF because it is a cascade sequence reaction involving reduction and etherification reactions over multifunctional acid catalysts. In this work, zirconium-based catalysts were facilely prepared from a zirconium salt, sulfosalicylic acid, and biomass by a simple hydrothermal method. The obtained catalyst with both Brønsted and Lewis acids (BA and LA, respectively) can transform HMF into BPMF with a yield of 92.4% in 2propanol by Meerwein−Ponndorf−Verley reduction and etherification in a one-pot strategy. Additionally, the reaction pathway and mechanism of the reductive etherification reaction was investigated and is presented. This work proposes an approach for the preparation of a solid acid catalyst with multifunctional BA and LA for reductive etherification of aldehydes to ethers.
Highly direct oxidative cyanation of alcohols provides
a promising
synthesis route for the cyanide-free synthesis of organic nitriles.
It is challenging to explore a noble metal-free catalyst for direct
conversion of alcohol to nitrile under ammonia conditions because
it is a three-step consecutive reaction. In the present work, the
CoO
x
/MnO2 catalyst was developed
for direct oxidative cyanation of benzyl alcohol to benzonitrile with
a yield of 86% and a selectivity of 91% with aqueous ammonia. The
selectivity to benzonitrile and benzamide can be tuned via water accelerating
the transformation of benzonitrile to benzamide. In addition, the
kinetic studies reveal that the first step of the oxidation of benzyl
alcohol is the rate-determining step for the consecutive reactions.
It is found that Mn species are the main active sites while Co species
are the co-catalyst for the titled reaction. Moreover, the starting
substrates employed in the present catalytic system can be expanded
to aliphatic, benzylic, allylic, and heterocyclic alcohols, which
demonstrates a sustainable strategy for the direct synthesis of nitrile
from alcohol while avoiding the use of the conventional toxic cyanide.
Oxygen-containing organics, which are generated from the selective oxidation of their corresponding hydrocarbons, have high value in the chemical and pharmaceutical industries. However, their oxidation reactions are very challenging as...
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