Electrocatalytic transformation of carbon dioxide (CO
) and water into chemical feedstocks offers the potential to reduce carbon emissions by shifting the chemical industry away from fossil fuel ...dependence. We provide a technoeconomic and carbon emission analysis of possible products, offering targets that would need to be met for economically compelling industrial implementation to be achieved. We also provide a comparison of the projected costs and CO
emissions across electrocatalytic, biocatalytic, and fossil fuel-derived production of chemical feedstocks. We find that for electrosynthesis to become competitive with fossil fuel-derived feedstocks, electrical-to-chemical conversion efficiencies need to reach at least 60%, and renewable electricity prices need to fall below 4 cents per kilowatt-hour. We discuss the possibility of combining electro- and biocatalytic processes, using sequential upgrading of CO
as a representative case. We describe the technical challenges and economic barriers to marketable electrosynthesized chemicals.
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.
Choosing from the heart De Luna, Phil
Science (American Association for the Advancement of Science),
2021-Apr-02, 2021-04-02, 20210402, Letnik:
372, Številka:
6537
Journal Article
Electrochemical reduction of carbon dioxide (CO^sub 2^) to carbon monoxide (CO) is the first step in the synthesis of more complex carbon-based fuels and feedstocks using renewable electricity1-7. ...Unfortunately, the reaction suffers from slow kinetics7,8 owing to the low local concentration of CO^sub 2^ surrounding typical CO^sub 2^ reduction reaction catalysts. Alkali metal cations are known to overcome this limitation through non-covalent interactions with adsorbed reagent species9,10, but the effect is restricted by the solubility of relevant salts. Large applied electrode potentials can also enhance CO^sub 2^ adsorption11, but this comes at the cost of increased hydrogen (H^sub 2^) evolution. Here we report that nanostructured electrodes produce, at low applied overpotentials, local high electric fields that concentrate electrolyte cations, which in turn leads to a high local concentration of CO^sub 2^ close to the active CO^sub 2^ reduction reaction surface. Simulations reveal tenfold higher electric fields associated with metallic nanometre-sized tips compared to quasi-planar electrode regions, and measurements using gold nanoneedles confirm a field-induced reagent concentration that enables the CO^sub 2^ reduction reaction to proceed with a geometric current density for CO of 22 milliamperes per square centimetre at -0.35 volts (overpotential of 0.24 volts). This performance surpasses by an order of magnitude the performance of the best gold nanorods, nanoparticles and oxidederived noble metal catalysts. Similarly designed palladium nanoneedle electrocatalysts produce formate with a Faradaic efficiency of more than 90 per cent and an unprecedented geometric current density for formate of 10 milliamperes per square centimetre at -0.2 volts, demonstrating the wider applicability of the field-induced reagent concentration concept.
Electrochemical reduction of CO2 is a compelling route to store renewable electricity in the form of carbon‐based fuels. Efficient electrochemical reduction of CO2 requires catalysts that combine ...high activity, high selectivity, and low overpotential. Extensive surface reconstruction of metal catalysts under high productivity operating conditions (high current densities, reducing potentials, and variable pH) renders the realization of tailored catalysts that maximize the exposure of the most favorable facets, the number of active sites, and the oxidation state all the more challenging. Earth‐abundant transition metals such as tin, bismuth, and lead have been proven stable and product‐specific, but exhibit limited partial current densities. Here, a strategy that employs bismuth oxyhalides as a template from which 2D bismuth‐based catalysts are derived is reported. The BiOBr‐templated catalyst exhibits a preferential exposure of highly active Bi (11¯0) facets. Thereby, the CO2 reduction reaction selectivity is increased to over 90% Faradaic efficiency and simultaneously stable current densities of up to 200 mA cm−2 are achieved—more than a twofold increase in the production of the energy‐storage liquid formic acid compared to previous best Bi catalysts.
A 2D bismuth oxyhalide‐templated catalyst for CO2 electroreduction exhibits an in operando preferential facet exposure, which enables sustaining near‐unity selectivity to formate production even at high current densities up to 200 mA cm−2.
Earth-abundant first-row (3d) transition metal–based catalysts have been developed for the oxygen-evolution reaction (OER); however, they operate at overpotentials substantially above thermodynamic ...requirements. Density functional theory suggested that non-3d high-valency metals such as tungsten can modulate 3d metal oxides, providing near-optimal adsorption energies for OER intermediates. We developed a room-temperature synthesis to produce gelled oxyhydroxides materials with an atomically homogeneous metal distribution. These gelled FeCoW oxyhydroxides exhibit the lowest overpotential (191 millivolts) reported at 10 milliamperes per square centimeter in alkaline electrolyte. The catalyst shows no evidence of degradation after more than 500 hours of operation. X-ray absorption and computational studies reveal a synergistic interplay between tungsten, iron, and cobalt in producing a favorable local coordination environment and electronic structure that enhance the energetics for OER.
The electrocatalytic carbon dioxide reduction reaction (CO2RR) addresses the need for storage of renewable energy in valuable carbon-based fuels and feedstocks, yet challenges remain in the ...improvement of electrosynthesis pathways for highly selective hydrocarbon production. To improve catalysis further, it is of increasing interest to lever synergies between heterogeneous and homogeneous approaches. Organic molecules or metal complexes adjacent to heterogeneous active sites provide additional binding interactions that may tune the stability of intermediates, improving catalytic performance by increasing Faradaic efficiency (product selectivity), as well as decreasing overpotential. We offer a forward-looking perspective on molecularly enhanced heterogeneous catalysis for CO2RR. We discuss four categories of molecularly enhanced strategies: molecular-additive-modified heterogeneous catalysts, immobilized organometallic complex catalysts, reticular catalysts and metal-free polymer catalysts. We introduce present-day challenges in molecular strategies and describe a vision for CO2RR electrocatalysis towards multi-carbon products. These strategies provide potential avenues to address the challenges of catalyst activity, selectivity and stability in the further development of CO2RR.The carbon dioxide reduction reaction can enable renewable energy storage by producing valuable products such as ethylene. This Perspective provides an overview of strategies that use molecular enhancement of heterogeneous catalysts to improve activity, efficiency and selectivity.
Using renewable energy to recycle CO2 provides an opportunity to both reduce net CO2 emissions and synthesize fuels and chemical feedstocks. It is of central importance to design electrocatalysts ...that both are efficient and can access a tunable spectrum of products. Syngas, a mixture of carbon monoxide (CO) and hydrogen (H2), is an important chemical precursor that can be converted downstream into small molecules or larger hydrocarbons by fermentation or thermochemistry. Many processes that utilize syngas require different syngas compositions: we therefore pursued the rational design of a family of electrocatalysts that can be programmed to synthesize different designer syngas ratios. We utilize in situ surface-enhanced Raman spectroscopy and first-principles density functional theory calculations to develop a systematic picture of CO* binding on Cu-enriched Au surface model systems. Insights from these model systems are then translated to nanostructured electrocatalysts, whereby controlled Cu enrichment enables tunable syngas production while maintaining current densities greater than 20 mA/cm2.
In hydrogen production, the anodic oxygen evolution reaction (OER) limits the energy conversion efficiency and also impacts stability in proton-exchange membrane water electrolyzers. Widely used ...Ir-based catalysts suffer from insufficient activity, while more active Ru-based catalysts tend to dissolve under OER conditions. This has been associated with the participation of lattice oxygen (lattice oxygen oxidation mechanism (LOM)), which may lead to the collapse of the crystal structure and accelerate the leaching of active Ru species, leading to low operating stability. Here we develop Sr–Ru–Ir ternary oxide electrocatalysts that achieve high OER activity and stability in acidic electrolyte. The catalysts achieve an overpotential of 190 mV at 10 mA cm–2 and the overpotential remains below 225 mV following 1,500 h of operation. X-ray absorption spectroscopy and 18O isotope-labeled online mass spectroscopy studies reveal that the participation of lattice oxygen during OER was suppressed by interactions in the Ru–O–Ir local structure, offering a picture of how stability was improved. The electronic structure of active Ru sites was modulated by Sr and Ir, optimizing the binding energetics of OER oxo-intermediates.
The electrochemical reduction of carbon monoxide is a promising approach for the renewable production of carbon-based fuels and chemicals. Copper shows activity toward multi-carbon products from CO ...reduction, with reaction selectivity favoring two-carbon products; however, efficient conversion of CO to higher carbon products such as n-propanol, a liquid fuel, has yet to be achieved. We hypothesize that copper adparticles, possessing a high density of under-coordinated atoms, could serve as preferential sites for n-propanol formation. Density functional theory calculations suggest that copper adparticles increase CO binding energy and stabilize two-carbon intermediates, facilitating coupling between adsorbed *CO and two-carbon intermediates to form three-carbon products. We form adparticle-covered catalysts in-situ by mediating catalyst growth with strong CO chemisorption. The new catalysts exhibit an n-propanol Faradaic efficiency of 23% from CO reduction at an n-propanol partial current density of 11 mA cm
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