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
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.
Electrochemical carbon dioxide (CO2) reduction is a promising strategy to synthesize valuable multi-carbon products (C2+) while sequestering CO2 and utilizing intermittent renewable electricity. For ...industrial deployment, CO2 electrolyzers must remain stable while selectively producing concentrated C2+ products at high rates with modest cell voltages. Here, we present a membrane electrode assembly (MEA) electrolyzer that converts CO2 to C2+ products. We perform side-by-side comparisons of state-of-the-art electrolyzer systems and find that the MEA provides the most stable cell voltage and product selectivity. We then demonstrate an approach to release concentrated gas and liquid products from the cathode outlet. This strategy achieves ∼50% and ∼80% Faradaic efficiency for ethylene and C2+ products, respectively, with cathode outlet concentrations of ∼30% ethylene and the direct production of ∼4 wt % ethanol. We characterize stability by operating continuously for 100 h, the longest stable ethylene production at current densities >100 mA cm−2 among reported CO2 electrolyzers.
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•Membrane electrode assembly design enables stable CO2 electroreduction•∼50% Faradaic efficiency for ethylene and ∼80% Faradaic efficiency for C2+ products•>30% gas outlet concentration of ethylene and direct production of ∼4 wt % ethanol•Continuous 100 h operation at >100 mA cm−2
The advent of low-cost renewable electricity and rising atmospheric CO2 has led to a focus on electrochemical CO2 reduction as a means toward low-carbon-intensity fuels and chemical feedstocks. The conversion of CO2 into C2+ hydrocarbons and oxygenates (i.e., products containing two or more carbon atoms) is attractive in light of large global market demand for these high-energy-density products. A limited number of prior studies have focused on performance in the reaction rate regime above 100 mA cm−2 generally viewed as necessary for industrial deployment. In these works, gas diffusion electrodes are used in liquid electrolyte electrochemical flow cells, which suffer in system stability and/or energy efficiency. We overcome this issue by developing a membrane electrode assembly-based electrolyzer. The combined catalyst and system strategy produces concentrated gas and liquid products and maintains performance during long-term (100 h) uninterrupted operation.
Electrochemical CO2 reduction is a promising strategy to synthesize valuable multi-carbon products (C2+) while sequestering CO2 and utilizing intermittent renewable electricity. Here, we present a stable membrane electrode assembly (MEA) electrolyzer that converts CO2 to C2+ products. This strategy achieves ∼50% and ∼80% selectivity for ethylene and C2+ products, respectively, with cathode outlet concentrations of ∼30% ethylene and the direct production of ∼4 wt % ethanol. We characterize stability by operating continuously for 100 h with steady ethylene production.
The upgrading of CO
/CO feedstocks to higher-value chemicals via energy-efficient electrochemical processes enables carbon utilization and renewable energy storage. Substantial progress has been made ...to improve performance at the cathodic side; whereas less progress has been made on improving anodic electro-oxidation reactions to generate value. Here we report the efficient electroproduction of value-added multi-carbon dimethyl carbonate (DMC) from CO and methanol via oxidative carbonylation. We find that, compared to pure palladium controls, boron-doped palladium (Pd-B) tunes the binding strength of intermediates along this reaction pathway and favors DMC formation. We implement this doping strategy and report the selective electrosynthesis of DMC experimentally. We achieve a DMC Faradaic efficiency of 83 ± 5%, fully a 3x increase in performance compared to the corresponding pure Pd electrocatalyst.
The oxygen evolution reaction (OER) limits the energy efficiency of electrocatalytic systems due to the high overpotential symptomatic of poor reaction kinetics; this problem worsens over time if the ...performance of the OER electrocatalyst diminishes during operation. Here, a novel synthesis of nanocrystalline Ni–Co–Se using ball milling at cryogenic temperature is reported. It is discovered that, by anodizing the Ni–Co–Se structure during OER, Se ions leach out of the original structure, allowing water molecules to hydrate Ni and Co defective sites, and the nanoparticles to evolve into an active Ni–Co oxyhydroxide. This transformation is observed using operando X‐ray absorption spectroscopy, with the findings confirmed using density functional theory calculations. The resulting electrocatalyst exhibits an overpotential of 279 mV at 0.5 A cm−2 and 329 mV at 1 A cm−2 and sustained performance for 500 h. This is achieved using low mass loadings (0.36 mg cm−2) of cobalt. Incorporating the electrocatalyst in an anion exchange membrane water electrolyzer yields a current density of 1 A cm−2 at 1.75 V for 95 h without decay in performance. When the electrocatalyst is integrated into a CO2‐to‐ethylene electrolyzer, a record‐setting full cell voltage of 3 V at current density 1 A cm−2 is achieved.
A scalable synthesis method of nanocrystalline metal selenides is developed to achieve both high activity and stability of electrocatalysts used for water oxidation, important for green hydrogen production. The formation of defective and coordinatively unsaturated sites by milling at cryogenic temperatures facilitates the hydration of metal sites to form active nanosized oxyhydroxides.
Blood-brain barrier (BBB) dysfunction is associated with worse epilepsy outcomes however the underlying molecular mechanisms of BBB dysfunction remain to be elucidated. Tight junction proteins are ...important regulators of BBB integrity and in particular, the tight junction protein claudin-5 is the most enriched in brain endothelial cells and regulates size-selectivity at the BBB. Additionally, disruption of claudin-5 expression has been implicated in numerous disorders including schizophrenia, depression and traumatic brain injury, yet its role in epilepsy has not been fully deciphered. Here we report that claudin-5 protein levels are significantly diminished in surgically resected brain tissue from patients with treatment-resistant epilepsy. Concomitantly, dynamic contrast-enhanced MRI in these patients showed widespread BBB disruption. We show that targeted disruption of claudin-5 in the hippocampus or genetic heterozygosity of claudin-5 in mice exacerbates kainic acid-induced seizures and BBB disruption. Additionally, inducible knockdown of claudin-5 in mice leads to spontaneous recurrent seizures, severe neuroinflammation, and mortality. Finally, we identify that RepSox, a regulator of claudin-5 expression, can prevent seizure activity in experimental epilepsy. Altogether, we propose that BBB stabilizing drugs could represent a new generation of agents to prevent seizure activity in epilepsy patients.
The synthesis and photophysical evaluation of two enatiomerially pure dimetallic lanthanide luminescent triple-stranded helicates is described. The two systems, formed from the chiral (R,R) ligand 1 ...and (S,S) ligand 2, were produced as single species in solution, where the excitation of either the naphthalene antennae or the pyridiyl units gave rise to Eu(III) emission in a variety of solvents. Excitation of the antennae also gave rise to circularly polarized Eu(III) luminescence emissions for Eu(2):1(3) and Eu(2):2(3) that were of equal intensity and opposite sign, confirming their enantiomeric nature in solution providing a basis upon which we were able to assign the absolute configurations of Eu(2):1(3) and Eu(2):2(3).
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