216 research outputs found
Electrochemical CO2 reduction in membrane-electrode assemblies
No full textElectrochemical conversion of gaseous CO2 to value-added products and fuels is a promising approach to achieve net-zero CO2 emission energy systems. Significant efforts have been achieved in the design and synthesis of highly active and selective electrocatalysts for this reaction and their reaction mechanism. To perform an efficient conversion and desired product selectivity in practical applications, we need an active, cost-effective, stable, and scalable electrolyzer design. Membrane-electrode assemblies (MEAs) can be an efficient solution to address the key challenges in the aqueous gas diffusion electrodes (GDE), e.g., ohmic resistances and complex reactor design. This review presents a critical overview of recent advances in experimental design and simulation of MEAs for CO2 reduction reaction, including the shortcomings and remedial strategies. In the last section, the remaining challenges and future research opportunities are suggested to support the advancement of CO2 electrochemical technologies.Lei Ge, Hesamoddin Rabiee, Mengran Li, Siddhartha Subramanian, Yao Zheng, Joong Hee Lee, Thomas Burdyny, Hao Wan
Determining the Fate of Methane Released from the Seafloor in Deep and Shallow Water Environments
Full text linkMarine gas seeps and accidental marine oil spills are sources of methane (CH_(4)) to the ocean, and potentially to the atmosphere, though the magnitude of the fluxes and dynamics of these systems are poorly defined. For example, the ultimate capacity of aerobic CH_(4) oxidation, a process converting CH_(4) to carbon dioxide (CO_(2)) and biomass in most ocean waters, is unknown. Deeper water environments may provide a longer conduit for CH_(4) to transit before atmosphere emission and thus a higher likelihood for an oxidative fate. Shallow water environments may provide a shorter conduit for CH_(4) to transit before being emitted to the atmosphere, however, these environments often have some of the highest rates of primary production causing pCO_(2) to be undersaturated. Thus the biochemical conversion of CH_(4) to CO_(2) may not enable this released carbon to be emitted to the atmosphere. To better constrain these variables in natural environments, studies of dissolved oxygen (DO) concentration, CH4 concentration and stable isotopic ratios were conducted at two contrasting sites: the Deepwater Horizon (DWH) oil spill in the Gulf of Mexico (GoM) and the natural seep field near Coal Oil Point (COP), CA.
The investigation of 1316 DO profiles measured from 11 May until 20 September 2010 revealed the spatial and temporal variability of bulk hydrocarbon respiration in these deep and intermediate plumes since DO is removed during hydrocarbon respiration. These analyses suggest that the general movement of these plumes was toward the southwest, and that a total mass of 0.18��0.05 Tg hydrocarbon in the plume layers was fully respired to CO_(2), and 0.10��0.08 Tg hydrocarbon was incorporated into biomass (i.e. conversion efficiency 0.36��0.11 mg biomass/mg hydrocarbon). A stable isotope model incorporating measurements of CH_(4) concentrations, CH_(4) oxidation rates, and current velocity was developed to determine CH_(4) oxidation rates, as well as the flow rate from the seafloor. This model was tested on 20 samples taken from 1 to 12 km from the wellhead from 11 June through 20 June 2010 during the DWH oil spill. Results suggest that the rate of CH4 oxidation ranged from 22 to 844 nM d^(-1) in mid-June 2010 and that the rate of flow from the Macondo well was 8.4��10^(7) moles d^(-1), both of which are in agreement with previous estimates determined independently.
High-resolution measurements of sea surface CH_(4) and CO_(2) concentrations and air-sea fluxes were conducted at the COP seep field. Results suggest that the diffusive air-sea fluxes of CH_(4) and CO_(2) were 0.18��0.19 mmol m^(-2) day^(-1) and -1.65��1.23 mmol m^(-2) day^(-1), respectively, and that the extent of microbial oxidation of CH_(4) was insufficient to change this shallow water environment from a sink of atmospheric CO_(2) to a source.
The seeps at COP released CH_(4) into waters at a rate that was an order of magnitude less than that from the DWH oil spill, and resulted a plume area that was also an order of magnitude less. In total, these results suggest that microbial oxidation provides the dominant sink of the released CH_(4) at both sites
Aspects of the impact of artificial intelligence on advertising
Full text linkWith the development of the economy and the improvement of technology, artificial intelligence has also emerged, especially bringing about changes in the advertising industry. This article aims to study the application and impact of artificial intelligence on the advertising industry, analyze its role in precise advertising placement, creative strategies, and effectiveness evaluation, and focus on the privacy breaches and ethical technical risks brought by artificial intelligence while assisting the intelligent transformation of the advertising industry
Advancing integrated CO<sub>2</sub> electrochemical conversion with amine-based CO<sub>2</sub> capture: a review
No full textCarbon dioxide (CO2) electrolysis is a promising route to utilise captured CO2 as a building block to produce valuable feedstocks and fuels such as carbon monoxide and ethylene. Very recently, CO2 electrolysis has been proposed as an alternative process to replace the amine recovery unit of the commercially available amine-based CO2 capture process. This process would replace the most energy-intensive unit operation in amine scrubbing while providing a route for CO2 conversion. The key enabler for such process integration is to develop an efficient integrated electrolyser that can convert CO2 and recover the amine simultaneously. Herein, this review provides an overview of the fundamentals and recent progress in advancing integrated CO2 conversion in amine-based capture media. This review first discusses the mechanisms for both CO2 absorption in the capture medium and electrochemical conversion of the absorbed CO2. We then summarise recent advances in improving the efficiency of integrated electrolysis via innovating electrodes, tailoring the local reaction environment, optimising operation conditions (e.g., temperatures and pressures), and modifying cell configurations. This review is concluded with future research directions for understanding and developing integrated CO2 electrolysers.ChemE/Materials for Energy Conversion and Storag
The Ionomer-Catalyst Interfacial Interactions during Electrochemical CO2 Reduction: An operando approach
No full textElectrochemical CO2 reduction (CO2R) provides the opportunity to mitigate our fossil-carbon dependence, by using CO2 as an alternative source to produce value-added chemicals. Especially multi-carbon (C2+) products are industrially of high value and hence a promising candidate for CO2R products. Copper is uniquely capable of producing these value-added C2+ products. Currently, the application of CO2R technology is hampered by low selectivity and rates of C2+ products. Ionomers, or ion-conducting polymers, are used in the catalyst layer to optimize the local reaction environment. In particular Nafion, a cation exchange ionomer, has proven to promote C2+ formation, but the mechanism behind it remains unclear. For this thesis, we focused on elucidating the role of the Nafion ionomer in altering product distribution on copper. A planar Cu electrode was used, onto which the Nafion was drop-casted. Atomic force microscopy was used to observe the restructuring of the ionomer during CO2R, while attenuated total reflection surface enhanced infrared spectroscopy (ATR-SEIRAS) enabled us to observe adsorbed chemical intermediate species during electrochemical CO2R. Flow cell experiments were performed to study the effect of the ionomer on product distribution and activity. The addition of Nafion significantly increased formation towards ethylene, due to stabilization of the atop-CO intermediate. The ionomer layer underwent restructuring during CO2R, where it is expected that the hydrophilic domain of the ionomer takes over the surface interactions from the hydrophobic backbone, due to electrowetting of the catalyst. With the insights gained in this thesis we elucidated the interactions between the ionomer and catalyst during electrochemical CO2R, which relates to the fundamental understanding required for designing advanced catalyst layers in the gas diffusion electrode.Electrical Engineering | Sustainable Energy Technolog
Regulating the reaction zone of electrochemical CO<sub>2</sub> reduction on gas-diffusion electrodes by distinctive hydrophilic-hydrophobic catalyst layers
No full textRegulating the rational wettability on gas-diffusion electrodes (GDEs) plays a pivotal role to improve the efficiency of CO2RR via fine-tuning the reaction zone and boosting the formation of triple-phase interfaces. Herein, we present a wettability regulation strategy that modulates the triple-phase reaction zone in the catalyst layer of GDEs. This strategy was employed on a flow-through hollow fiber GDE coated with a Bi-embedded catalyst layer. Compared to other ex-situ methods (e.g., adding wetting agents) affecting the bulk of electrocatalysts or catalyst layer, we create distinctive hydrophilic-hydrophobic regions within the catalyst layer. Catalyst layer with hydrophilic-hydrophobic regions outperforms the fully hydrophilic one by facilitating the species transport, boosting triple-phase interface formation, and maximizing the active sites. This regulation strategy showed stable wettability during CO2RR cathodic conditions, evidenced by the direct measurement of penetration depth. The electrode with the regulated wettability exhibited over 80% catalyst utilization and 4 times higher formate partial current density (~150 mA cm−2 with FEformate> 90%) compared to the untreated electrode, outperforming other GDEs employed for CO2RR to formate in the same concentrations of bicarbonate. The finding of this versatile microenvironment regulation strategy can be extended to GDEs used for other gas-phase reactions.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.ChemE/Materials for Energy Conversion and Storag
Sandwich-like heterostructured nanomaterials immobilized laccase for the degradation of phenolic pollutants and boosted enzyme stability
No full textA novel magnetic 2D/2D heterogeneous structure MXene@NiFe-LDH@Fe3O4 was prepared for immobilization of laccase. In this work, two-dimensional MXene nanosheets with abundant surface functional groups were heterogeneously assembled with layered double hydroxide (LDH) by in situ co-precipitation method, and magnetic nanoparticle Fe3O4 with excellent biocompatibility and rapid separation of materials and substrates was introduced subsequently, and then silane coupling agent was coated on the surface of MXene@NiFe-LDH@Fe3O4. The functionalized MXene@NiFe-LDH@Fe3O4 was employed as a carrier to immobilize laccase from Trametes-Versicolor. The enzyme loading of the nanocomposite material is as high as 167.9 mg/g. Compared with free enzymes, the immobilized laccase showed a notable improvement in stability in a wider range of pHs (2.0–8.0), temperatures (25–60 °C), and organic solvent concentration (1–5 M). The reusability study suggested that after 7 cycles of repeated catalysis, the degradation efficiency could reach 55.5% for 2,4-dichlorophenol, 92.1% for bisphenol A and70.9% for pyrocatechol. The results provide a new carrier preparation strategy for the efficient immobilization of laccase.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.ChemE/Materials for Energy Conversion and Storag
Mitigating Electrolyte Flooding for Electrochemical CO<sub>2</sub>Reduction via Infiltration of Hydrophobic Particles in a Gas Diffusion Layer
No full textAchieving operational stability at high current densities remains a challenge in CO2 electrolyzers due to flooding of the gas diffusion layer (GDL) that supports the electrocatalyst. We mitigated electrode flooding at high current densities using a vacuum-assisted infiltration method to embed 200-400 nm-sized polytetrafluoroethylene (PTFE) particles at the interface of the microporous layer (MPL) and carbon cloth in a commercial GDL. In CO2 electrolysis to CO over a silver nanoparticle catalyst on the GDL, the PTFE-embedded GDL not only just exhibited less than 10% of the electrolyte seepage rates observed in untreated GDLs at a current density of 300 mA·cm-2 but also expanded the electrochemical active area across the testing conditions. The PTFE-embedded GDL also maintained a Faradaic efficiency for CO2 electrolysis to CO above 80% for more than 100 h at 100 mA·cm-2, which was a 50-fold improvement in the stable operation time of the electrolyzer. Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.ChemE/Materials for Energy Conversion and Storag
The role of electrode wettability in electrochemical reduction of carbon dioxide
No full textThe electrochemical reduction of carbon dioxide (CO2RR) requires access to ample gaseous CO2and liquid water to fuel reactions at high current densities for industrial-scale applications. Substantial improvement of the CO2RR rate has largely arisen from positioning the catalyst close to gas-liquid interfaces, such as in gas-diffusion electrodes. These requirements add complexity to an electrode design that no longer consists of only a catalyst but also a microporous and nanoporous network of gas-liquid-solid interfaces of the electrode. In this three-dimensional structure, electrode wettability plays a pivotal role in the CO2RR because the affinity of the electrode surface by water impacts the observed electrode reactivity, product selectivity, and long-term stability. All these performance metrics are critical in an industrial electrochemical process. This review provides an in-depth analysis of electrode wettability's role in achieving an efficient, selective, and stable CO2RR performance. We first discuss the underlying mechanisms of electrode wetting phenomena and the foreseen ideal wetting conditions for the CO2RR. Then we summarize recent advances in improving cathode performance by altering the wettability of the catalyst layer of gas-diffusion electrodes. We conclude the review by discussing the current challenges and opportunities to develop efficient and selective cathodes for CO2RR at industrially relevant rates. The insights generated from this review could also benefit the advancement of other critical electrochemical processes that involve multiple complex flows in porous electrodes, such as electrochemical reduction of carbon monoxide, oxygen, and nitrogen.ChemE/Materials for Energy Conversion and Storag
Reconfigurable metacavity antenna-based microwave computational imaging
No full textIn this paper, a reconfigurable metacavity antenna (RMA) is proposed to generate sufficient measurement modes for implementing microwave computational imaging (MCI) within a limited bandwidth. The RMA is essentially a metacavity antenna, with its back side replaced by a reconfigurable metasurface and its top surface etched with circular leaky irises. By altering the on/off states of the PIN diodes loaded onto the reconfigurable metasurface, the resonant mode inside the metacavity is modulated, thereby radiating chaotic wavefronts. These lowcorrelated radiated fields can be used to encode the imaging scene, which are referred to as measurement modes in an MCI system. MCI experiments are conducted at 20 GHz using full-wave simulations. Two configurations, RMA-to-probe and RMA-to-RMA, are analyzed, highlighting the enhanced imaging performance achieved under the RMA-to-RMA layout.<br/
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