1,720,961 research outputs found
Evaluating Bicarbonate Electrolyzer Configurations for Energy‐Efficient Formate Production
Full text linkReactive carbon capture (RCC) by direct conversion of CO2 capture solutions has emerged as a promising alternative to gas-fed electrolyzers. Leveraging bicarbonate electrolyzers (BEs), RCC eliminates energy-intensive steps such as CO2 regeneration and pressurization. Additionally, BEs prevent failures like carbonate salt deposition common in gas-fed systems. However, intrinsic challenges in BEs, such as higher cell voltages and lower faradaic efficiencies (FEs), result in greater energy consumption during electrolysis compared to gas-fed electrolyzers. To evaluate whether an RCC chain (RCCC) is more energy-efficient for formate production than a gas-fed carbon chain (GFCC), the study optimizes the BE configuration and compares it to a valorization chain requiring a pure, pressurized CO2 stream for gas-fed electrolyzers. This study shows the most efficient BE setup employs a cation exchange membrane paired with a buffer layer, achieving a FE for formate of ≈75% at a current density of 100 mA cm−2 and a cell potential of 3.1 V. Using this optimized BE, the RCCC demonstrates an energetic advantage over GFCCs in scenarios without CO2 recycling. Even with 100% CO2 utilization enabled by recycling systems, RCCC remains competitive. With potential improvements in BE performance, RCCC emerges as a promising strategy for converting CO2 into formate efficiently
A deeper understanding of flooding dynamics in gas diffusion electrodes for CO2 electrolyzer: how interfacial pressure shapes gas–liquid stability
Full text linkGas-fed CO2 electrolyzers are a promising technology for sustainable fuel and chemical production, but their industrial deployment is limited by the instability of gas diffusion electrodes (GDEs), particularly in microfluidic flow cells (MFCs). A key failure mechanism is electrode flooding, which discontinues CO2 transport and favours hydrogen evolution. Although pressure control across the gas–liquid interface has emerged as a strategy to mitigate flooding, the precise role of differential pressure (ΔP) between gas and liquid side of the GDE remains poorly understood and inconsistently defined in literature. In this work, we systematically explore how gas and liquid pressure management alters the GDE interface, focusing on the understudied “flow-by” regime. Using Cu nanoparticles as a model catalyst and operating at industrially relevant current densities (0.5 A cm−2), we monitor flooding dynamics through real-time pressure readings, product selectivity analysis, electrochemical impedance spectroscopy (EIS) and field emission scanning electron microscopy (FE-SEM) in different electrochemical setups with several commercial Gas Diffusion Layers (GDL). Our results demonstrate that a ΔP of 30 mbar can fully suppress flooding, preserving catalyst performance and enabling selective CO2 reduction for over 6 h at 0.5 A cm−2, almost an order-of-magnitude improvement over uncontrolled system. The experimental ΔP value is confirmed by multiphysics simulations, by modelling capillary-driven liquid invasion and gas transport, in which a predicted onset value of 20 mbar is defined as the required value to prevent the flooding. This work provides the first integrated framework combining pressure tuning, diagnostics, and multi-physics simulation to define and optimize flow-by operation, offering actionable insights for designing robust, high-performance CO2 electrolyzers
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Novel Microfluidic Septum to Optimize Energy Recovery in Single-Chamber Microbial Fuel Cells
Full text linkThis study proposes a redesign of asymmetric single-chamber microbial fuel cells (a-SCMFCs) with the goal of optimizing energy production. In the present work, the new approach is based on the introduction of a novel intermediate microfluidic septum (IMS) inside the electrolyte chamber. This IMS was designed as a relatively simple and inexpensive method to optimize both electrolyte flow and species transfer inside the devices. a-SCMFCs, featuring the IMS, are compared to control cells (IMS-less), when operated with sodium acetate as the carbon energy source. Performances of cells are evaluated in terms both of maximum output potential achieved, and energy recovery (Erec) as the ratio between the energy yield and the inner electrolyte volume. The a-SCMFCs with the novel IMS are demonstrated to enhance the energy recovery compared to control cells exhibiting Erec values of (37 ± 1) J/m3, which is one order of magnitude higher than that achieved by control cells (3.0 ± 0.3) J/m3. Concerning the maximum output potential, IMS cells achieve (2.8 ± 0.2) mV, compared to control cells at (0.68 ± 0.07) mV. Furthermore, by varying the sodium acetate concentration, the Erec and maximum potential output values change accordingly. By monitoring the activity of a-SCMFCs for over one year, the beneficial impact of the IMS on both the initial inoculation phase and the long-term stability of electrical performance are observed. These improvements support the effectiveness of IMS to allow the development of efficient biofilms, likely due to the reduction in oxygen cross-over towards the anode. Electrochemical characterizations confirm that the presence of the IMS impacts the diffusion processes inside the electrolytic chamber, supporting the hypothesis of a beneficial effect on oxygen cross-over
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Metabolic Engineering of E. coli for Enhanced Diols Production from Acetate
Full text linkEffective employment of renewable carbon sources is highly demanded to develop sustainable biobased manufacturing. Here, we developed Escherichia coli strains to produce 2,3-butanediol and acetoin (collectively referred to as diols) using acetate as the sole carbon source by stepwise metabolic engineering. When tested in fed-batch experiments, the strain overexpressing the entire acetate utilization pathway was found to consume acetate at a 15% faster rate (0.78 ± 0.05 g/g/h) and to produce a 35% higher diol titer (1.16 ± 0.01 g/L) than the baseline diols-producing strain. Moreover, singularly overexpressing the genes encoding alternative acetate uptake pathways as well as alternative isoforms of genes in the malate-to-pyruvate pathway unveiled that leveraging ackA-pta and maeA is more effective in enhancing acetate consumption and diols production, compared to acs and maeB. Finally, the increased substrate consumption rate and diol production obtained in flask-based experiments were confirmed in bench-scale bioreactors operated in fed-batch mode. Consequently, the highest titer of 1.56 g/L achieved in this configuration increased by over 30% compared to the only other similar effort carried out so far
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