3 research outputs found
Highly Stable and Efficient Catalyst with In Situ Exsolved Fe–Ni Alloy Nanospheres Socketed on an Oxygen Deficient Perovskite for Direct CO<sub>2</sub> Electrolysis
The massive emission
of carbon dioxide (CO<sub>2</sub>), the major
portion of greenhouse gases, has negatively affected our ecosystem.
Developing new technologies to effectively reduce CO<sub>2</sub> emission
or convert CO<sub>2</sub> to useful products has never been more imperative.
In response to this challenge, we herein developed novel in situ exsolved
Fe–Ni alloy nanospheres uniformly socketed on an oxygen-deficient
perovskite [LaÂ(Sr)ÂFeÂ(Ni)] as a highly stable and efficient catalyst
for the effective conversion of CO<sub>2</sub> to carbon monoxide
(CO) in a high-temperature solid oxide electrolysis cell (HT-SOEC).
The symmetry between the reduction and reoxidation cycles of this
catalyst indicates its good redox reversibility. The cathodic reaction
kinetics for CO<sub>2</sub> electrolysis is significantly improved
with a polarization resistance as low as 0.272 Ω cm<sup>2</sup>. In addition, a remarkably enhanced current density of 1.78 A cm<sup>–2</sup>, along with a high Faraday efficiency (∼98.8%),
was achieved at 1.6 V and 850 °C. Moreover, the potentiostatic
stability test of up to 100 h showed that the cell was stable without
any noticeable coking in a CO<sub>2</sub>/CO (70:30) flow at an applied
potential of 0.6 V (vs OCV) and 850 °C. The increased oxygen
vacancies together with the in situ exsolved nanospheres on the perovskite
backbone ensures sufficiently active sites and consequently improves
the electrochemical performance for the efficient CO<sub>2</sub> conversion.
Therefore, this newly developed perovskite can be a promising cathode
material for HT-SOEC. More generally, this study points to a new direction
to develop highly efficient catalysts in the form of the perovskite
oxides with perfectly in situ exsolved metal/bimetal nanospheres
Rational Design of Silver Sulfide Nanowires for Efficient CO<sub>2</sub> Electroreduction in Ionic Liquid
Electroreduction
of CO<sub>2</sub> holds the promise for the utilization
of CO<sub>2</sub> and the storage of intermittent renewable energy.
The development of efficient catalysts for effectively converting
CO<sub>2</sub> to fuels has never been more imperative. Herein, we
successfully synthesized Ag<sub>2</sub>S nanowires (NWs) dominating
at the facet of (121) using a modified facile one-step method and
utilized them as a catalyst for electrochemical CO<sub>2</sub> reduction
reaction (CO<sub>2</sub>RR). Ag<sub>2</sub>S NWs in ionic liquid (IL)
possess a partial current density of 12.37 mA cm<sup>–2</sup>, ∼14- and ∼17.5-fold higher than those of Ag<sub>2</sub>S NWs and bulk Ag in KHCO<sub>3</sub>, respectively. Moreover, it
shows significantly higher selectivity with a value of 92.0% at the
overpotential (η) of −0.754 V. More importantly, the
CO formation begins at a low η of 54 mV. The good performance
originates from not only the presence of [EMIM–CO<sub>2</sub>]<sup>+</sup> complexes but also the specific facet contribution.
The partial density of states (PDOS) and work functions reveal that
the d band center of the surface Ag atom of Ag<sub>2</sub>SÂ(121) is
closer to the Fermi energy level and has a higher d-electron density
than those of Ag(111) and Ag55, which lowers transition state energy
for CO<sub>2</sub>RR. Besides, density functional theory (DFT) calculations
indicate that the COOH* formation over Ag<sub>2</sub>S is energetically
more favorable on (111) and (121) facets than that on Ag(111) and
Ag55. Therefore, we conclude that the significantly enhanced performance
of Ag<sub>2</sub>S NWs in IL synergistically originates from the solvent-assisted
and specific facet-promoted contributions. This distinguishes Ag<sub>2</sub>S NWs in IL as an attractive and selective platform for CO<sub>2</sub>RR
Shape-Dependent Electrocatalytic Reduction of CO<sub>2</sub> to CO on Triangular Silver Nanoplates
Electrochemical reduction of CO<sub>2</sub> (CO<sub>2</sub>RR)
provides great potential for intermittent renewable energy storage.
This study demonstrates a predominant shape-dependent electrocatalytic
reduction of CO<sub>2</sub> to CO on triangular silver nanoplates
(Tri-Ag-NPs) in 0.1 M KHCO<sub>3</sub>. Compared with similarly sized
Ag nanoparticles (SS-Ag-NPs) and bulk Ag, Tri-Ag-NPs exhibited an
enhanced current density and significantly improved Faradaic efficiency
(96.8%) and energy efficiency (61.7%), together with a considerable
durability (7 days). Additionally, CO starts to be observed at an
ultralow overpotential of 96 mV, further confirming the superiority
of Tri-Ag-NPs as a catalyst for CO<sub>2</sub>RR toward CO formation.
Density functional theory calculations reveal that the significantly
enhanced electrocatalytic activity and selectivity at lowered overpotential
originate from the shape-controlled structure. This not only provides
the optimum edge-to-corner ratio but also dominates at the facet of
Ag(100) where it requires lower energy to initiate the rate-determining
step. This study demonstrates a promising approach to tune electrocatalytic
activity and selectivity of metal catalysts for CO<sub>2</sub>RR by
creating optimal facet and edge site through shape-control synthesis