Paper-based microfluidic fuel cells emerge as a promising clean energy sources for small-scale electronic devices, while their broad-based applications require a comprehensive understanding of their ...structure-performance relationships. Here in this work, we made attempt to identify the key structural parameters that impact the overall performance of paper-based microfluidic fuel cells. The influences of fuel crossover, cell resistance, limitations from both anode and cathode, and in particular microfluidic paper channel properties have been systemically investigated and optimized towards the best practices. Among various structural parameters, we unravel for the first time that the overall performance of these paper-based microfluidic fuel cells is largely dependent on the textural properties of microfluidic paper channels. By correlating the fuel cell performance with the unambiguously determined flow rate of electrolyte within different paper channels, we found that a greater flow rate which was achieved by using paper with larger mean pore diameter, could result in higher peak power density and open circuit voltage. This performance enhancement would benefit from minimized reactant depletion near electrode surfaces and suppressed fuel crossover. Technically, an open circuit voltage of 0.86 V and a maximum power density of 7.10 mW/cm2 can be achieved on a single cell (fuel: 4 M KCOOH; oxidant: air; electrolyte: 1 M KOH; catalyst: 0.2 mg/cm2 Pd/C on 0.15 cm2 graphite foil), and the maximum power output can be sustained for at least 1 h. The fuel cell power can also be easily increased proportionally when connecting two or more cells in series, which makes theses paper-based microfluidic fuel cells capable to power various electronic devices with different power requirements.
Ionic liquids in electrocatalysis Zhang, Gui-Rong; Etzold, Bastian J.M.
Journal of energy chemistry,
March 2016, 2016-03-00, 20160301, Letnik:
25, Številka:
2
Journal Article
Recenzirano
The performance of an electrocatalyst, which is needed e.g. for key energy conversion reactions such as hydrogen evolution, oxygen reduction or CO2 reduction, is determined not only by the inherent ...structure of active sites but also by the properties of the interfacial structures at catalytic surfaces. Ionic liquids (ILs), as a unique class of metal salts with melting point below 100°C, present themselves as ideal modulators for manipulations of the interfacial structures. Due to their excellent properties such as good chemical stability, high ionic conductivity, wide electrochemical windows and tunable solvent properties the performance of electrocatalysts can be substantially improved through ILs. In the current minireview, we highlight the critical role of the IL phase at the microenvironments created by the IL, the liquid electrolyte, catalytic nanoparticles and/or support materials, by detailing the promotional effect of IL in electrocatalysis as reaction media, binders, and surface modifiers. Updated exemplary applications of IL in electrocatalysis are given and moreover, the latest developments of IL modified electrocatalysts following the “Solid Catalyst with Ionic Liquid Layer (SCILL)” concept are presented.
Ionic liquids, as versatile molecules with numerous unique properties, have shown great promise to boost the performance of electrocatalytic systems. Display omitted
This study investigates the importance of preconditioning in Pt‐alloy catalysts for oxygen–reduction reactions. Previous research indicated that slower scanning rates during preconditioning initially ...boost activity, but this is followed by a rapid decline. The study reveals the required number of cycles to achieve the first constant steady state activity in PtNiMo/C catalysts when using slower scanning rates during preconditioning. It also highlights the resulting activity differences. Remarkably, a catalyst preconditioned with 150 slow cycles showed an activity of approximately 1.25 mA cm−2 at 0.90 VRHE, significantly higher than one preconditioned at a fast rate (0.82 mA cm−2). Both ex–situ and in–situ analyses revealed that Pt, along with Ni, was leached during pretreatment. At slower scan rates of 20 mV s−1, the dissolved Pt redeposited as highly active, small‐sized clusters or single atoms. Fast scan rates of of 500 mV s−1, in contrast, resulted in fewer such clusters. Accelerated stress tests up to 1.10 VRHE confirmed the high stability of these clusters, demonstrating a substantial activity increase even after 24,000 cycles.
Chances in the preconditioning of Pt alloy catalysts have a huge impact to the specific activity outcome. A slow pretreatment at 20 mV s−1 results in a fast increase, strong drop and reaching nearly steady state activities at high cycle numbers. Alongside a change in the octahedral PtNiMo/C catalyst to Pt clusters is observed.
In article number 2010977, Bastian J. M. Etzold and Gui‐Rong Zhang review the emerging applications of solid catalysts with an ionic liquid layer for electrocatalysts in key energy storage/conversion ...processes. Alongside case studies, the history, latest progress, and mechanistic underpinnings of the roles of ionic liquids are critically discussed and key challenges and future opportunities outlined.
Pt‐based alloy catalysts supported on carbon are commonly characterized for oxygen reduction reaction (ORR) activity using the rotating disk electrode technique (RDE). Within this study, we show ...exemplarily for PtNiMo/C catalysts that the applied pretreatment influences strongly the determined activity. The classically employed descriptor of unchanged cyclic voltammetry response is insufficient to portrait completed surface restructuring, and gives an incorrect impression that stable activity can be determined. This might be one of the reasons for the strongly deviating activities reported in literature. Following the changes in activity during pretreatment also with in‐situ FTIR and online dissolution measurements gives insights to an up to now largely overseen high activity of the trimetallic catalysts. A maximum activity of 0.57 mA cmPt−2 at 0.95 VRHE is reached quickly during the first six cycles and decreases slowly subsequently. The maximum activity and change of activity over the cycle number is affected by the scan rate and electrolyte refreshing, while the gas atmosphere plays only a minor role. This exemplary study might be important for Pt alloy catalysts in general.
An up to now unknown activity development is achieved during the pretreatment of alloyed trimetallic PtNiMo/C catalysts. In addition to the recording of steady state CVs under electrochemical cleaning cycles, insight into the unconditioned specific activity of the catalyst reveals a sharp increase during the first five to eight cycles and a further decrease at higher cycle numbers.
Heavy-metal pollution poses severe threat to ecological systems and presents a great challenge for global sustainability. Portable point-of-care sensing platform for detection/monitoring of ...heavy-metal pollution in the environment is urgently demanded. Herein, a highly sensitive, robust, and low-cost microfluidic electrochemical carbon-based sensor (μCS) for detection of trace heavy metals is presented. The miniaturized μCS devices are based on a microfluidic paper channel combined with a novel three-dimensional layout with working and counter electrodes facing each other and analyte flowing along the microfluidic channel between these two electrodes. Pristine graphite foil free of any surface modifier is not only used as the electronically conductive pad but also directly employed as the working electrode for fabricating the μCS. The resulting simple and portable device was applied in Cd2+ and Pb2+ detection using square-wave anodic stripping voltammetry. Detection limits down to 1.2 μg/L for Cd2+ and 1.8 μg/L for Pb2+ can be achieved over the μCS. The μCS devices are also found to be highly robust, and 10 repetitive measurements with a single μCS device resulted to be highly reproducible.
Paper‐based microfluidics is characteristic of fluid transportation through spontaneous capillary action of paper and has exhibited great promise for a variety of applications especially for sensing. ...Furthermore, paper‐based microfluidics enables the design of miniaturized electrochemical devices to be applied in the energy sector, which is especially attractive for the rapid growing market of small size disposable electronics. This review gives a brief summary on the basics of paper chemistry and capillary‐driven microfluidic behavior, and highlights recent advances of paper‐based microfluidics in developing electrochemical sensing devices and miniaturized energy storage/conversion devices. Their structural features, working principles and exemplary applications are comprehensively elaborated and discussed. Additionally, this review also points out the existing challenges and future opportunities of paper‐based microfluidic electronics.
Paper‐based microfluidics emerges as a powerful and versatile platform for constructing simple, inexpensive, environmentally‐friendly and high‐performing miniaturized electrochemical devices for various applications. This review summarizes the basics of paper‐based microfluidics and highlights some recent advances of paper‐based microfluidics in developing electrochemical sensing and energy storage/conversion devices. Their structural features, working principle and exemplary applications are comprehensively elaborated and discussed. This review also points out the existing challenges and future opportunities of paper‐based microfluidic electronics.
Non-precious metal catalysts show great promise to replace the state-of-the-art Pt-based catalysts for catalyzing the oxygen reduction reaction (ORR), while their catalytic activity still needs to be ...greatly improved before their broad-based application. Here, we report a facile approach to improving the performance of zeolitic imidazolate framework-derived carbon (ZDC) toward the ORR by incorporating a small amount of ionic liquid (IL). The IL would preferentially fill the micropores of ZDC and greatly enhance the utilization of the active sites within the micropores, which are initially not accessible due to insufficient surface wetting. It is also disclosed that the ORR activity in terms of kinetic current at 0.85 V depends on the loading amount of the IL, and the maximum activity is obtained at a mass ratio of IL to ZDC at 1.2. The optimum stems from the counterbalance between the enhanced utilization of the active sites within the micropores and the retarded diffusion of the reactants within the IL phase due to its high viscosity.
Abstract Background Breast implant-associated anaplastic large-cell lymphoma (BIA-ALCL) is a rare, Non-Hodgkin lymphoma arising in the capsule of breast implants. BIA-ALCL presents as a recurrent ...effusion and/or mass. Tumours exhibit CD30 expression and are negative for anaplastic lymphoma kinase (ALK). We report the multi-disciplinary management of the UK series and how the stage of disease may be used to stratify treatment. Methodsmaterials-methods Between 2012 and 2016, 23 cases of BIA-ALCL were diagnosed in 15 regional centres throughout the UK. Data on breast implant surgeries, clinical features, treatment and follow-up were available for 18 patients. Results The mean lead-time from initial implant insertion to diagnosis was 10 years (range: 3-16). All cases were observed in patients with textured breast implants or expanders. Fifteen patients with breast implants presented with stage I disease (capsule confined), and were treated with implant removal and capsulectomy. One patient received adjuvant chest-wall radiotherapy. Three patients presented with extra-capsular masses (stage IIA). In addition to explantation, capsulectomy and excision of the mass, all patients received neo-/adjuvant chemotherapy with CHOP as first line. One patient progressed on CHOP but achieved pathological complete response (pCR) with Brentuximab Vedotin. After a mean follow-up of 23 months (range: 1-56) all patients reported here remain disease-free. Discussion BIA-ALCL is a rare neoplasm with a good prognosis. Our data support the recommendation that stage I disease be managed with surgery alone. Adjuvant chemotherapy may be required for more invasive disease and our experience has shown the efficacy of Brentuximab as a second line treatment.
Electrocatalytic oxidation of 5‐hydroxymethylfurfural (HMF) offers a renewable approach to produce the value‐added platform chemical 2,5‐furandicarboxylic acid (FDCA). The key for the economic ...viability of this approach is to develop active and selective electrocatalysts. Nevertheless, a reliable catalyst evaluation protocol is still missing, leading to elusive conclusions on criteria for a high‐performing catalyst. Herein, we demonstrate that besides the catalyst identity, secondary parameters such as materials of conductive substrates for the working electrode, concentration of the supporting electrolyte, and electrolyzer configurations have profound impact on the catalyst performance and thus need to be optimized before assessing the true activity of a catalyst. Moreover, we highlight the importance of those secondary parameters in suppressing side reactions, which has long been overlooked. The protocol is validated by evaluating the performance of free‐standing Cu‐foam, and CuCoO modified with NaPO2H2 and Ni, which were immobilized on boron‐doped diamond (BDD) electrodes. Recommended practices and figure of merits in carefully evaluating the catalyst performance are proposed.
Proposal of a measurement protocol for comparison of electrocatalysts for the HMF oxidation with standard evaluation (yield, faradaic efficiency), as well as a new figure of merit (production rate) to compare catalysts independent from setup size. Additionally, the alkaline degradation of HMF is evaluated and taken into account for closing the mass balance in order to assess the true catalyst activity.
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