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.
The electrochemical reduction of CO2 is a promising route to convert intermittent renewable energy to storable fuels and valuable chemical feedstocks. To scale this technology for industrial ...implementation, a deepened understanding of how the CO2 reduction reaction (CO2RR) proceeds will help converge on optimal operating parameters. Here, a techno‐economic analysis is presented with the goal of identifying maximally profitable products and the performance targets that must be met to ensure economic viability—metrics that include current density, Faradaic efficiency, energy efficiency, and stability. The latest computational understanding of the CO2RR is discussed along with how this can contribute to the rational design of efficient, selective, and stable electrocatalysts. Catalyst materials are classified according to their selectivity for products of interest and their potential to achieve performance targets is assessed. The recent progress and opportunities in system design for CO2 electroreduction are described. To conclude, the remaining technological challenges are highlighted, suggesting full‐cell energy efficiency as a guiding performance metric for industrial impact.
Electrochemical CO2 reduction is a viable pathway to utilize CO2 and store renewable electricity in the form of fuels and chemical feedstocks. Starting with a techno‐economic analysis, the state‐of‐the‐art mechanistic understanding and the latest developments in catalyst and system design for CO2 electrolysis are discussed, concluding with the remaining technological challenges and opportunities for future development.
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.
A very basic pathway from CO2 to ethyleneEthylene is an important commodity chemical for plastics. It is considered a tractable target for synthesizing renewable resources from carbon dioxide (CO2). ...The challenge is that the performance of the copper electrocatalysts used for this conversion under the required basic reaction conditions suffers from the competing reaction of CO2 with the base to form bicarbonate. Dinh et al. designed an electrode that tolerates the base by optimizing CO2 diffusion to the catalytic sites (see the Perspective by Ager and Lapkin). This catalyst design delivers 70% efficiency for 150 hours.Science, this issue p. 783; see also p. 707Carbon dioxide (CO2) electroreduction could provide a useful source of ethylene, but low conversion efficiency, low production rates, and low catalyst stability limit current systems. Here we report that a copper electrocatalyst at an abrupt reaction interface in an alkaline electrolyte reduces CO2 to ethylene with 70% faradaic efficiency at a potential of −0.55 volts versus a reversible hydrogen electrode (RHE). Hydroxide ions on or near the copper surface lower the CO2 reduction and carbon monoxide (CO)–CO coupling activation energy barriers; as a result, onset of ethylene evolution at −0.165 volts versus an RHE in 10 molar potassium hydroxide occurs almost simultaneously with CO production. Operational stability was enhanced via the introduction of a polymer-based gas diffusion layer that sandwiches the reaction interface between separate hydrophobic and conductive supports, providing constant ethylene selectivity for an initial 150 operating hours.
The syndrome of uraemic cardiomyopathy, characterised by left ventricular hypertrophy, diffuse fibrosis and systolic and diastolic dysfunction, is common in chronic kidney disease and is associated ...with an increased risk of cardiovascular morbidity and mortality. The pathophysiological mechanisms leading to uraemic cardiomyopathy are not fully understood. We suggest that coronary microvascular dysfunction may be a key mediator in the development of uraemic cardiomyopathy, a phenomenon that is prevalent in other myocardial diseases that share phenotypical similarities with uraemic cardiomyopathy such as hypertrophic cardiomyopathy and heart failure with preserved ejection fraction. Here, we review the current understanding of uraemic cardiomyopathy, highlight different methods of assessing coronary microvascular function and evaluate the current evidence for coronary microvascular dysfunction in chronic kidney disease.
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.
Coincident signaling by dopamine and glutamate is thought to be crucial for a variety of motivated behaviors. Previous work has suggested that some midbrain dopamine neurons are themselves capable of ...glutamate corelease, but this phenomenon remains poorly understood. Here, we expressed the light-activated cation channel Channelrhodopsin-2 (ChR2) in genetically defined midbrain dopamine neurons to stimulate exocytosis specifically from dopaminergic terminals in both the nucleus accumbens (NAc) shell and dorsal striatum of brain slices from adult mice. Optical activation resulted in robust glutamate-mediated EPSCs in all medium spiny neurons examined in the NAc shell. In contrast, optically evoked glutamatergic currents were nearly undetectable in the dorsal striatum. Further, we used a conditional knock-out mouse lacking vesicular glutamate transporter 2 (VGLUT2) specifically in dopamine neurons to determine whether VGLUT2 is required for the exocytotic release of glutamate from dopamine neurons. Our data show that conditional knock-out completely abolished all optically evoked glutamate release. These results provide definitive physiological evidence for VGLUT2-mediated glutamate release by mature dopamine neurons projecting to the NAc shell, but not to the dorsal striatum. Thus, the unique ability of NAc-projecting dopamine neurons to synchronously activate both dopamine and glutamate receptors may have crucial implications for the ability to respond to motivationally significant stimuli.
In 2017, the National Association of Peer Supporters (N.A.P.S.) leadership became aware of growing member concerns about supervision contradicting or conflicting with core peer support values. In ...response, N.A.P.S. established a work group that revised the association's 2013 National Practice Guidelines for Peer Supporters to include specific guidance to supervisors (i.e., the National Practice Guidelines for Peer Specialists and Supervisors). The new guidelines are not intended to address administrative or other basic functions of supervision; instead, they offer expertise and practical guidance to supervisors of peer support workers in understanding the core values of mutual support and managing the complexities of the nonclinical role in settings that may have different values and priorities.
The use of flow photochemistry and its apparent superiority over batch has been reported by a number of groups in recent years. To rigorously determine whether flow does indeed have an advantage over ...batch, a broad range of synthetic photochemical transformations were optimized in both reactor modes and their yields and productivities compared. Surprisingly, yields were essentially identical in all comparative cases. Even more revealing was the observation that the productivity of flow reactors varied very little to that of their batch counterparts when the key reaction parameters were matched. Those with a single layer of fluorinated ethylene propylene (FEP) had an average productivity 20 % lower than that of batch, whereas three‐layer reactors were 20 % more productive. Finally, the utility of flow chemistry was demonstrated in the scale‐up of the ring‐opening reaction of a potentially explosive 1.1.1 propellane with butane‐2,3‐dione.
Spot the difference! By careful matching of reaction parameters, the performance of 13 different photochemical reactions were compared in both batch and flow reactors. Surprisingly, the yields obtained in the different reactor modes were essentially identical. Similarly, the productivity differences between the two reactor modes, under the same time scales, were relatively small (see figure).
Introduction:
Mitochondrial dysfunction is linked to a variety of human diseases. Understanding the dynamic alterations in mitochondrial respiration at various stages of development is important to ...our understanding of disease progression. Zebrafish provide a system for investigating mitochondrial function and alterations during different life stages. The purpose of this study was to investigate our ability to measure mitochondrial oxygen consumption rates in zebrafish embryos, larvae, and adults as an indicator of mitochondrial function.
Methods:
Basal respiration of entire zebrafish embryos (5 dpf), larvae (0.6–0.9 cm), young adults (3-month-old), and old adults (12-month-old) was measured using an Oroboros Oxygraph, with a stirrer speed of 26 rpm. For embryos and larvae, “leak” respiration (plus oligomycin), maximum respiration (plus uncoupler), non-mitochondrial respiration (plus inhibitors), and complex IV activity were also measured. To induce physical activity in adult fish, the stirrer speed was increased to 200 rpm.
Results and Discussion:
We demonstrate the ability to accurately measure respiration rates in zebrafish at various ages using the Oroboros Oxygraph. When comparing zebrafish embryos to larvae, embryos have a higher maximum respiration. Three-month-old zebrafish males have higher basal respiration than females, while 12-month-old zebrafish females exhibit greater rates of respiration than males and younger females. When the stirrer speed was increased, respiration rates decrease, but with differences depending on sex. This study demonstrates a simple and accessible method to assess zebrafish physiology by mitochondrial oxygen consumption measurements in an unmodified Oroboros Oxygraph. The method should facilitate studies to understand the intricate interplay between mitochondrial function, development, and aging.
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