Abstract
Electrochemical reduction of CO
2
to multi-carbon products (C
2+
), when powered using renewable electricity, offers a route to valuable chemicals and fuels. In conventional neutral-media CO
...2
-to-C
2+
devices, as much as 70% of input CO
2
crosses the cell and mixes with oxygen produced at the anode. Recovering CO
2
from this stream adds a significant energy penalty. Here we demonstrate that using a liquid-to-liquid anodic process enables the recovery of crossed-over CO
2
via facile gas-liquid separation without additional energy input: the anode tail gas is directly fed into the cathodic input, along with fresh CO
2
feedstock. We report a system exhibiting a low full-cell voltage of 1.9 V and total carbon efficiency of 48%, enabling 262 GJ/ton ethylene, a 46% reduction in energy intensity compared to state-of-art single-stage CO
2
-to-C
2+
devices. The strategy is compatible with today’s highest-efficiency electrolyzers and CO
2
catalysts that function optimally in neutral and alkaline electrolytes.
Abstract
In alkaline and neutral MEA CO
2
electrolyzers, CO
2
rapidly converts to (bi)carbonate, imposing a significant energy penalty arising from separating CO
2
from the anode gas outlets. Here we ...report a CO
2
electrolyzer uses a bipolar membrane (BPM) to convert (bi)carbonate back to CO
2
, preventing crossover; and that surpasses the single-pass utilization (SPU) limit (25% for multi-carbon products, C
2+
) suffered by previous neutral-media electrolyzers. We employ a stationary unbuffered catholyte layer between BPM and cathode to promote C
2+
products while ensuring that (bi)carbonate is converted back, in situ, to CO
2
near the cathode. We develop a model that enables the design of the catholyte layer, finding that limiting the diffusion path length of reverted CO
2
to ~10 μm balances the CO
2
diffusion flux with the regeneration rate. We report a single-pass CO
2
utilization of 78%, which lowers the energy associated with downstream separation of CO
2
by 10× compared with past systems.
Abstract
The electrochemical conversion of CO
2
to methane provides a means to store intermittent renewable electricity in the form of a carbon-neutral hydrocarbon fuel that benefits from an ...established global distribution network. The stability and selectivity of reported approaches reside below technoeconomic-related requirements. Membrane electrode assembly-based reactors offer a known path to stability; however, highly alkaline conditions on the cathode favour C-C coupling and multi-carbon products. In computational studies herein, we find that copper in a low coordination number favours methane even under highly alkaline conditions. Experimentally, we develop a carbon nanoparticle moderator strategy that confines a copper-complex catalyst when employed in a membrane electrode assembly. In-situ XAS measurements confirm that increased carbon nanoparticle loadings can reduce the metallic copper coordination number. At a copper coordination number of 4.2 we demonstrate a CO
2
-to-methane selectivity of 62%, a methane partial current density of 136 mA cm
−2
, and > 110 hours of stable operation.
Abstract
Electrochemical CO
2
reduction (CO
2
R) is an approach to closing the carbon cycle for chemical synthesis. To date, the field has focused on the electrolysis of ambient pressure CO
2
. ...However, industrial CO
2
is pressurized—in capture, transport and storage—and is often in dissolved form. Here, we find that pressurization to 50 bar steers CO
2
R pathways toward formate, something seen across widely-employed CO
2
R catalysts. By developing
operando
methods compatible with high pressures, including quantitative
operando
Raman spectroscopy, we link the high formate selectivity to increased CO
2
coverage on the cathode surface. The interplay of theory and experiments validates the mechanism, and guides us to functionalize the surface of a Cu cathode with a proton-resistant layer to further the pressure-mediated selectivity effect. This work illustrates the value of industrial CO
2
sources as the starting feedstock for sustainable chemical synthesis.
Coupling electrochemical CO2 reduction (CO2R) with a renewable energy source to create high‐value fuels and chemicals is a promising strategy in moving toward a sustainable global energy economy. ...CO2R liquid products, such as formate, acetate, ethanol, and propanol, offer high volumetric energy density and are more easily stored and transported than their gaseous counterparts. However, a significant amount (~30%) of liquid products from electrochemical CO2R in a flow cell reactor cross the ion exchange membrane, leading to the substantial loss of system‐level Faradaic efficiency. This severe crossover of the liquid product has—until now—received limited attention. Here, we review promising methods to suppress liquid product crossover, including the use of bipolar membranes, solid‐state electrolytes, and cation‐exchange membranes‐based acidic CO2R systems. We then outline the remaining challenges and future prospects for the production of concentrated liquid products from CO2.
Here we review promising methods to suppress liquid product crossover in flow cell reactor including the use of bipolar membranes, solid‐state electrolytes, and cation‐exchange membranes based acidic CO2R systems. The elimination of liquid product crossover is thus a key step to advance the achievement of renewable liquid fuels from CO2
Abstract
Renewable CH
4
produced from electrocatalytic CO
2
reduction is viewed as a sustainable and versatile energy carrier, compatible with existing infrastructure. However, conventional alkaline ...and neutral CO
2
-to-CH
4
systems suffer CO
2
loss to carbonates, and recovering the lost CO
2
requires input energy exceeding the heating value of the produced CH
4
. Here we pursue CH
4
-selective electrocatalysis in acidic conditions via a coordination method, stabilizing free Cu ions by bonding Cu with multidentate donor sites. We find that hexadentate donor sites in ethylenediaminetetraacetic acid enable the chelation of Cu ions, regulating Cu cluster size and forming Cu-N/O single sites that achieve high CH
4
selectivity in acidic conditions. We report a CH
4
Faradaic efficiency of 71% (at 100 mA cm
−2
) with <3% loss in total input CO
2
that results in an overall energy intensity (254 GJ/tonne CH
4
), half that of existing electroproduction routes.
Electrosynthesis of acetate from CO offers the prospect of a low-carbon-intensity route to this valuable chemical--but only once sufficient selectivity, reaction rate and stability are realized. It ...is a high priority to achieve the protonation of the relevant intermediates in a controlled fashion, and to achieve this while suppressing the competing hydrogen evolution reaction (HER) and while steering multicarbon (C
) products to a single valuable product--an example of which is acetate. Here we report interface engineering to achieve solid/liquid/gas triple-phase interface regulation, and we find that it leads to site-selective protonation of intermediates and the preferential stabilization of the ketene intermediates: this, we find, leads to improved selectivity and energy efficiency toward acetate. Once we further tune the catalyst composition and also optimize for interfacial water management, we achieve a cadmium-copper catalyst that shows an acetate Faradaic efficiency (FE) of 75% with ultralow HER (<0.2% H
FE) at 150 mA cm
. We develop a high-pressure membrane electrode assembly system to increase CO coverage by controlling gas reactant distribution and achieve 86% acetate FE simultaneous with an acetate full-cell energy efficiency (EE) of 32%, the highest energy efficiency reported in direct acetate electrosynthesis.
Targeted axillary dissection (TAD) includes biopsy of clipped lymph node and sentinel lymph nodes. However, clinical evidence regarding clinical feasibility and oncological safety of non-radioactive ...TAD in a real-world cohort remains limited.
In this prospective registry study, patients routinely underwent clip insertion into biopsy-confirmed lymph node. Eligible patients received neoadjuvant chemotherapy followed by axillary surgery. Main endpoints included the false-negative rate (FNR) of TAD and nodal recurrence rate.
Data from 353 eligible patients were analyzed. After completion of neoadjuvant chemotherapy, 85 patients directly proceeded to axillary lymph node dissection (ALND), furthermore, TAD with or without ALND was performed in 152 and 85 patients, respectively. Overall detection rate of clipped node was 94.9% (95% CI, 91.3-97.4%) and FNR of TAD was 12.2% (95% CI, 6.0-21.3%) in our study, with FNR decreasing to 6.0% (95% CI, 1.7-14.6%) in initially cN1 patients. During a median follow-up of 36.6 months, 3 nodal recurrences occurred (3/237 with ALND; 0/85 with TAD alone), with a 3-year freedom-from-nodal-recurrence rate of 100.0% among the TAD-only patients and 98.7% among the ALND patients with axillary pathologic complete response ( P =0.29).
TAD is feasible in initially cN1 breast cancer patients with biopsy-confirmed nodal metastases. ALND can safely be foregone in patients with negativity or a low volume of nodal positivity on TAD, with a low nodal failure rate and no compromise of 3-year recurrence-free survival.
Direct electrolysis of pH‐neutral seawater to generate hydrogen is an attractive approach for storing renewable energy. However, due to the anodic competition between the chlorine evolution and the ...oxygen evolution reaction (OER), direct seawater splitting suffers from a low current density and limited operating stability. Exploration of catalysts enabling an OER overpotential below the hypochlorite formation overpotential (≈490 mV) is critical to suppress the chloride evolution and facilitate seawater splitting. Here, a proton‐adsorption‐promoting strategy to increase the OER rate is reported, resulting in a promoted and more stable neutral seawater splitting. The best catalysts herein are strong‐proton‐adsorption (SPA) materials such as palladium‐doped cobalt oxide (Co3–xPdxO4) catalysts. These achieve an OER overpotential of 370 mV at 10 mA cm−2 in pH‐neutral simulated seawater, outperforming Co3O4 by a margin of 70 mV. Co3–xPdxO4 catalysts provide stable catalytic performance for 450 h at 200 mA cm−2 and 20 h at 1 A cm−2 in neutral seawater. Experimental studies and theoretical calculations suggest that the incorporation of SPA cations accelerates the rate‐determining water dissociation step in neutral OER pathway, and control studies rule out the provision of additional OER sites as a main factor herein.
Direct electrolysis of pH‐neutral seawater is not only a promising approach to produce clean hydrogen energy, but also of great significance to seawater desalination. Now, both the simulations and experimental characterizations illustrate that incorporating the strong‐proton‐adsorption cations into Co3O4 can increase the rate‐determining water dissociation step and achieve industrially required current density of >200 mA cm−2 in natural seawater.
The electrochemical reduction of CO2 is a promising route to convert carbon emissions into valuable chemicals and fuels. In electrolyzers producing multi-carbon products, 70%–95% of the supplied CO2 ...is converted to (bi)carbonates, limiting the carbon efficiency of electrochemical CO2 conversion. These (bi)carbonate anions can be lost to the aqueous electrolyte, converted back to gaseous CO2 and diluted in the anode tail gas, and/or combined with alkali metal cations from the electrolyte to form solid salt precipitates. Here, we report a microchanneled solid electrolyte that allows for the recapture and recycling of (bi)carbonate ions before reaching the anode, reducing CO2 loss to ∼3%. We demonstrate CO2 electroreduction to multi-carbon products with 77% selectivity without the use of alkali metal cations, by incorporating fixed quaternary ammonium cations. This system simultaneously achieves near-zero CO2 loss, high selectivity toward multi-carbon products, and stable operation at an industrially relevant current density over 200 h.
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•MSE reduces CO2RR reactant loss to near-zero (∼3%)•Fixed cations in the MSE enable alkali metal cation free operation•Selective multi-carbon production (77%) at industrially relevant current densities•Stable continuous electrolysis for >200 h at a current density of 100 mA cm−2
CO2 electrolysis is a promising technology to convert carbon emissions into valuable chemicals and fuels. In conventional CO2 electrolyzers, the majority of the reactant CO2 is lost to (bi)carbonate formation, limiting the carbon efficiency of electrochemical CO2 conversion. Here, we report a microchanneled solid electrolyte that allows for the internal recapture and recycle of (bi)carbonate ions before they are lost to the anode, drastically reducing the CO2 loss. By incorporating fixed quaternary ammonium cations, we demonstrate CO2 electroreduction to multi-carbon products without the use of alkali metal cations, the latter of which cause destructive salt precipitation. This system simultaneously achieves near-zero CO2 loss, high selectivity toward multi-carbon products, and stable operation at an industrially relevant current density.
CO2 electrolysis is a promising technology that can utilize intermittent renewable electricity to mitigate CO2 emissions. In conventional electrolyzers, most of the reactant CO2 is lost to parasitic side reactions, limiting the electrochemical conversion of CO2 into valuable products. Here, we present a microchanneled solid electrolyte that internally regenerates and recycles CO2, thereby eliminating CO2 loss. Implementing fixed cations in place of traditional alkali metal cations enables stable and selective CO2 electrolysis to multi-carbon products.
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