The sluggish kinetics of sulfur conversion in the cathode and the nonuniform deposition of lithium metal at the anode result in severe capacity decay and poor cycle life for lithium–sulfur (Li–S) batteries. Resolving these deficiencies is the most direct route toward achieving practical cells of this chemistry. Herein, a vertically aligned wood–derived carbon plate decorated with Co4N nanoparticles host (Co4N/WCP) is proposed that can serve as a host for both the sulfur cathode and the metallic lithium anode. This Co4N/WCP electrode host drastically enhances the reaction kinetics in the sulfur cathode and homogenizes the electric field at the anode for the uniform lithium plating. Density functional theory calculations confirm the experimental observations that Co4N/WCP provides a lower energy barrier for the polysulfide redox reaction in the cathode and a low adsorption energy for lithium deposition at the anode. Employing the Co4N/WCP host at both electrodes in a S@Co4N/WCP||Li@Co4N/WCP full cell delivers a specific capacity of 807.9 mAh g−1 after 500 cycles at a 1 C rate. Additional experiments are performed with high areal sulfur loading of 4 mg cm−2 to demonstrate the viability of this strategy for producing practical Li–S cells.
In certain metalloenzymes, multimetal centers with appropriate primary/secondary coordination environments allow carbon−carbon coupling reactions to occur efficiently and with high selectivity. This same function is seldom realized in molecular electrocatalysts. Herein we synthesized rod-shaped nanocatalysts with multiple copper centers through the molecular assembly of a triphenylphosphine copper complex (CuPPh). The assembled molecular CuPPh catalyst demonstrated excellent electrochemical CO 2 fixation performance in aqueous solution, yielding high-value C 2+ hydrocarbons (ethene) and oxygenates (ethanol) as the main products. Using density functional theory (DFT) calculations, in situ X-ray absorption spectroscopy (XAS) and quasi-in situ X-ray photoelectron spectroscopy (XPS), and reaction intermediate capture, we established that the excellent catalytic performance originated from the large number of double copper centers in the rod-shaped assemblies. Cu−Cu distances in the absence of CO 2 were as long as 7.9 Å, decreasing substantially after binding CO 2 molecules indicating dynamic and cooperative function. The double copper centers were shown to promote carbon−carbon coupling via a CO 2 transfer-coupling mechanism involving an oxalate (OOC−COO) intermediate, allowing the efficient production of C 2+ products. The assembled CuPPh nanorods showed high activity, excellent stability, and a high Faradaic efficiency (FE) to C 2+ products (65.4%), with performance comparable to state-of-the-art copper oxide-based catalysts. To our knowledge, our findings demonstrate that harnessing metalloenzyme-like properties in molecularly assembled catalysts can greatly improve the selectivity of CO2RR, promoting the rational design of improved CO2 reduction catalysts.
The Cu+/Cu0 interface in the Cu-based
electrocatalyst
is essential to promote the electrochemical reduction of carbon dioxide
(ERCO2) to produce multi-carbon hydrocarbons and alcohols
with high selectivity. However, due to the high activity of the Cu+/Cu0 interface, it is easy to be oxidized in the
air. How to control and prepare a Cu-based electrocatalyst with an
abundant and stable Cu+/Cu0 interface in situ
is a huge challenge. Here, combined with density functional theory
(DFT) calculations and experimental studies, we found that the trace
halide ions adsorbed on Cu2O can slow the reduction kinetics
of Cu+ → Cu0, which allowed us to in-situ
well control the synthesis of the CuO-derived electrocatalyst with
rich Cu+/Cu0 interfaces. Our Cu catalyst with
a rich Cu+/Cu0 interface exhibits excellent
ERCO2 performance. Under the operation potential of −0.98
V versus RHE, the Faraday efficiency of C2H4 and C2+ products are 55.8 and 75.7%, respectively, which
is about 16% higher than that of CuO-derived electrocatalysts that
do not use halide ions. The high
comes from the improvement of the coupling
efficiency of reaction intermediates such as CO–CO, which is
proved by DFT calculations, and the suppression of hydrogen evolution
reaction. Therefore, we provide an in-situ engineering strategy, which
is simple and effective for the design and preparation of high-performance
ERCO2 catalysts.
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