scholarly journals Electrocatalytic upcycling of polyethylene terephthalate to commodity chemicals and H2 fuel

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Hua Zhou ◽  
Yue Ren ◽  
Zhenhua Li ◽  
Ming Xu ◽  
Ye Wang ◽  
...  
Keyword(s):  
Polyethylene Terephthalate ◽  
Current Density ◽  
High Current Density ◽  
Value Added ◽  
Membrane Electrode Assembly ◽  
Membrane Electrode ◽  
Faradaic Efficiency ◽  
Commodity Chemicals ◽  
Low Crystalline ◽  
Crystalline Metal

AbstractPlastic wastes represent a largely untapped resource for manufacturing chemicals and fuels, particularly considering their environmental and biological threats. Here we report electrocatalytic upcycling of polyethylene terephthalate (PET) plastic to valuable commodity chemicals (potassium diformate and terephthalic acid) and H2 fuel. Preliminary techno-economic analysis suggests the profitability of this process when the ethylene glycol (EG) component of PET is selectively electrooxidized to formate (>80% selectivity) at high current density (>100 mA cm−2). A nickel-modified cobalt phosphide (CoNi0.25P) electrocatalyst is developed to achieve a current density of 500 mA cm−2 at 1.8 V in a membrane-electrode assembly reactor with >80% of Faradaic efficiency and selectivity to formate. Detailed characterizations reveal the in-situ evolution of CoNi0.25P catalyst into a low-crystalline metal oxy(hydroxide) as an active state during EG oxidation, which might be responsible for its advantageous performances. This work demonstrates a sustainable way to implement waste PET upcycling to value-added products.

scholarly journals Spatial reactant distribution in CO2 electrolysis: Balancing CO2 utilization and Faradaic Efficiency

2021 ◽  
Author(s):  
Siddhartha Subramanian ◽  
Joost Middelkoop ◽  
Thomas Burdyny
Keyword(s):  
Value Added ◽  
Membrane Electrode Assembly ◽  
Catalytic Performance ◽  
Membrane Electrode ◽  
Co2 Utilization ◽  
Faradaic Efficiency ◽  
Gas Channel ◽  
Spatially Resolved ◽  
Diffusion Layers ◽  
Trade Offs

The production of value added C1 and C2 compounds within CO2 electrolyzers has reached sufficient catalytic performance that system and process performance – such as CO2 utilization – have come more into consideration. Efforts to assess the limitations of CO2 conversion and crossover within electrochemical systems have been performed, providing valuable information to position CO2 electrolyzers within a larger process. Currently missing, however, is a clear elucidation of the inevitable trade-offs that exist between CO2 utilization and electrolyzer performance, specifically how the Faradaic Efficiency of a system varies with CO2 availability. Such information is needed to properly assess the viability of the technology. In this work, we provide a combined experimental and 3D modelling assessment of the trade-offs between CO2 utilization and selectivity at 200 mA/cm2 within a membrane-electrode assembly CO2 electrolyzer. Using varying inlet flow rates we demonstrate that the variation in spatial concentration of CO2 leads to spatial variations in Faradaic Efficiency that cannot be captured using common ‘black box’ measurement procedures. Specifically, losses of Faradaic efficiency are observed to occur even at incomplete CO2 consumption (80%). Modelling of the gas channel and diffusion layers indicated at least a portion of the H2 generated is considered as avoidable by proper flow field design and modification. The combined work allows for a spatially resolved interpretation of product selectivity occurring inside the reactor, providing the foundation for design rules in balancing CO2 utilization and device performance in both lab and scaled applications.

scholarly journals Durability of a recombination catalyst-based membrane-electrode assembly for electrolysis operation at high current density

2020 ◽  
Vol 279 ◽  
pp. 115809
Author(s):  
Fabiola Pantò ◽  
Stefania Siracusano ◽  
Nicola Briguglio ◽  
Antonino Salvatore Aricò
Keyword(s):  
Current Density ◽  
High Current Density ◽  
Membrane Electrode Assembly ◽  
Membrane Electrode ◽  
High Current

Critique and Improvement of a One-Dimensional Semianalytical Model of a Direct Methanol Fuel Cell

2012 ◽  
Vol 9 (5) ◽  
Author(s):  
C. C. Kuo ◽  
W. E. Lear ◽  
J. H. Fletcher ◽  
O. D. Crisalle
Keyword(s):  
Fuel Cell ◽  
Polarization Curve ◽  
Current Density ◽  
Direct Methanol Fuel Cell ◽  
Membrane Electrode Assembly ◽  
Membrane Electrode ◽  
One Dimensional ◽  
Implicit Equation ◽  
Direct Methanol ◽  
Methanol Fuel Cell

A constructive critique and a suite of proposed improvements for a recent one-dimensional semianalytical model of a direct methanol fuel cell are presented for the purpose of improving the predictive ability of the modeling approach. The model produces a polarization curve for a fuel cell system comprised of a single membrane-electrode assembly, based on a semianalytical one-dimensional solution of the steady-state methanol concentration profile across relevant layers of the membrane electrode assembly. The first improvement proposed is a more precise numerical solution method for an implicit equation that describes the overall current density, leading to better convergence properties. A second improvement is a new technique for identifying the maximum achievable current density, an important piece of information necessary to avoid divergence of the implicit-equation solver. Third, a modeling improvement is introduced through the adoption of a linear ion-conductivity model that enhances the ability to better match experimental polarization-curve data at high current densities. Fourth, a systematic method is advanced for extracting anodic and cathodic transfer-coefficient parameters from experimental data via a least-squares regression procedure, eliminating a potentially significant parameter estimation error. Finally, this study determines that the methanol concentration boundary condition imposed on the membrane side of the membrane-cathode interface plays a critical role in the model’s ability to predict the limiting current density. Furthermore, the study argues for the need to carry out additional experimental work to identify more meaningful boundary concentration values realized by the cell.

scholarly journals Optimization of Membrane Electrode Assembly of PEM Fuel Cell by Response Surface Method

Molecules ◽  
2019 ◽  
Vol 24 (17) ◽  
pp. 3097 ◽  
Author(s):  
Vuppala ◽  
Chedir ◽  
Jiang ◽  
Chen ◽  
Aziz ◽  
...  
Keyword(s):  
Fuel Cell ◽  
Response Surface ◽  
Response Surface Method ◽  
Current Density ◽  
Membrane Electrode Assembly ◽  
Proton Exchange ◽  
Cell Performance ◽  
Membrane Electrode ◽  
Membrane Thickness ◽  
Surface Method

The membrane electrode assembly (MEA) plays an important role in the proton exchange membrane fuel cell (PEMFC) performance. Typically, the structure comprises of a polymer electrolyte membrane sandwiched by agglomerate catalyst layers at the anode and cathode. Optimization of various parameters in the design of MEA is, thus, essential for reducing cost and material usage, while improving cell performance. In this paper, optimization of MEA is performed using a validated two-phase PEMFC numerical model. Key MEA parameters affecting the performance of a single PEMFC are determined from sensitivity analysis and are optimized using the response surface method (RSM). The optimization is carried out at two different operating voltages. The results show that membrane thickness and membrane protonic conductivity coefficient are the most significant parameters influencing cell performance. Notably, at higher voltage (0.8 V per cell), the current density can be improved by up to 40% while, at a lower voltage (0.6 V per cell), the current density may be doubled. The results presented can be of importance for fuel cell engineers to improve the stack performance and expedite the commercialization.

Selective Conversion of Carbon Dioxide to Formate with High Current Densities

2021 ◽  
pp. 2150001
Author(s):  
Xiulin Yang ◽  
Defei Liu ◽  
Shenghong Zhong ◽  
Xiaofeng Zhou ◽  
Kuo-Wei Huang ◽  
...  
Keyword(s):  
Current Density ◽  
Hollow Fiber ◽  
Active Sites ◽  
Large Scale ◽  
High Current Density ◽  
High Current ◽  
Faradaic Efficiency ◽  
Practical Applications ◽  
Selective Conversion ◽  
Current Densities

Selective conversion of CO2 to formate with high current densities is highly desirable but still challenging. Copper hollow fibers with interconnected pore structures were fabricated via a facile method and used as a stand-alone cathode for highly efficient electrochemical reduction of CO2 to formate. Our studies revealed that delivering the reactant CO2 gas to the inner space of the hollow fiber could build up a higher CO2 partial pressure in the pores and presumably reduce the concentration of H[Formula: see text] from the electrolyte to effectively suppress the major competing reaction, hydrogen evolution reaction (HER), from 46.9% faradaic efficiency (FE) to 15.0%. A high selectivity for CO2 reduction to formate with a maximum FE of 77.1% was achieved with a high current density of 34.7[Formula: see text]mA cm[Formula: see text], which is one of the highest FEs on Cu-based materials. Mechanistic studies suggest that the abundant active sites along with the unique crystal facets induced by the high pressure of CO2 at the pore surface in the “gas in” mode are attributed to the superior electroactivity and selectivity for the CO2 reduction to formate. The Cu hollow fiber electrodes exhibit an outstanding long-term stability at high current density, showing great potential for large-scale practical applications.

scholarly journals Boride-derived oxygen-evolution catalysts

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Ning Wang ◽  
Aoni Xu ◽  
Pengfei Ou ◽  
Sung-Fu Hung ◽  
Adnan Ozden ◽  
...  
Keyword(s):  
Oxygen Evolution ◽  
Current Density ◽  
Membrane Electrode Assembly ◽  
Membrane Electrode ◽  
Long Term Stability ◽  
Metal Borides ◽  
Current Densities ◽  
Alkaline Membrane ◽  
Co Reduction

AbstractMetal borides/borates have been considered promising as oxygen evolution reaction catalysts; however, to date, there is a dearth of evidence of long-term stability at practical current densities. Here we report a phase composition modulation approach to fabricate effective borides/borates-based catalysts. We find that metal borides in-situ formed metal borates are responsible for their high activity. This knowledge prompts us to synthesize NiFe-Boride, and to use it as a templating precursor to form an active NiFe-Borate catalyst. This boride-derived oxide catalyzes oxygen evolution with an overpotential of 167 mV at 10 mA/cm2 in 1 M KOH electrolyte and requires a record-low overpotential of 460 mV to maintain water splitting performance for over 400 h at current density of 1 A/cm2. We couple the catalyst with CO reduction in an alkaline membrane electrode assembly electrolyser, reporting stable C2H4 electrosynthesis at current density 200 mA/cm2 for over 80 h.

In-Situ Diagnostics of PEFCs

2009 ◽  
Author(s):  
Kaspar Andreas Friedrich ◽  
Norbert Wagner ◽  
Mathias Schulze
Keyword(s):  
Current Density ◽  
Measurement Techniques ◽  
Current Density Distribution ◽  
Electrical Energy ◽  
Membrane Electrode Assembly ◽  
Operating Conditions ◽  
Membrane Electrode ◽  
Mass Transport Effects ◽  
Electrical Energy Production

Polymer electrolyte fuel cells (PEFCs) are one of the most interesting alternatives for a pollution-free electrical energy production in many applications where a highly reliable source of electricity is needed. One of the major challenges in the development of PEFCs is to exploit the whole capacity that is inherent to a given membrane electrode assembly (MEA). In practice, certain obstacles remain to be overcome like local mass transport effects, non-uniformly manufactured MEAs, locally varying contact resistances, water management and temperature gradients. All these parameters lead to an inhomogeneous electrochemical activity over the electrode area. Consequently, a variation and a gradient of the current density over the cell area occurs which tends to result in inferior performance and low durability of a PEFC. For the determination of current density distribution different in-situ methods and measurement techniques are applied. Results can be used to improve cell components, to validate models and to detect inappropriate detrimental operating conditions of the fuel cell.

scholarly journals Nafion/Surface Modified Ceria Hybrid Membranes for Proton Exchange Fuel Cell Application

Polymers ◽  
2021 ◽  
Vol 13 (15) ◽  
pp. 2513
Author(s):  
Polina A. Yurova ◽  
Viktoria R. Malakhova ◽  
Ekaterina V. Gerasimova ◽  
Irina A. Stenina ◽  
Andrey B. Yaroslavtsev
Keyword(s):  
Fuel Cells ◽  
Current Density ◽  
Hydrogen Permeability ◽  
Composite Membranes ◽  
Membrane Electrode Assembly ◽  
Proton Exchange ◽  
Free Radical Scavengers ◽  
Membrane Electrode ◽  
Hybrid Membranes ◽  
A Current

Low chemical durability of proton exchange membranes is one the main factors limiting their lifetime in fuel cells. Ceria nanoparticles are the most common free radical scavengers. In this work, hybrid membranes based on Nafion-117 membrane and sulfonic or phosphoric acid functionalized ceria synthesized from various precursors were prepared by the in situ method for the first time. Ceria introduction led to a slight decrease in conductivity of hybrid membranes in contact with water. At the same time, conductivity of membranes containing sulfonic acid modified ceria exceeded that of the pristine Nafion-117 membrane at 30% relative humidity (RH). Hydrogen permeability decreased for composite membranes with ceria synthesized from cerium (III) nitrate, which correlates with their water uptake. In hydrogen-air fuel cells, membrane electrode assembly fabricated with the hybrid membrane containing ceria synthesized from cerium (IV) sulfate exhibited a peak power density of 433 mW/cm2 at a current density of 1080 mA/cm2, while operating at 60 °C and 70% RH. It was 1.5 times higher than for the pristine Nafion-117 membrane (287 mW/cm2 at a current density of 714 mA/cm2).

Chloride-mediated selective electrosynthesis of ethylene and propylene oxides at high current density

Science ◽  
2020 ◽  
Vol 368 (6496) ◽  
pp. 1228-1233 ◽  
Author(s):  
Wan Ru Leow ◽  
Yanwei Lum ◽  
Adnan Ozden ◽  
Yuhang Wang ◽  
Dae-Hyun Nam ◽  
...  
Keyword(s):  
Ethylene Oxide ◽  
Carbon Emissions ◽  
High Current Density ◽  
High Current ◽  
Renewable Electricity ◽  
Faradaic Efficiency ◽  
Commodity Chemicals ◽  
Current Densities ◽  
Global Carbon ◽  
Lower Carbon

Chemicals manufacturing consumes large amounts of energy and is responsible for a substantial portion of global carbon emissions. Electrochemical systems that produce the desired compounds by using renewable electricity offer a route to lower carbon emissions in the chemicals sector. Ethylene oxide is among the world’s most abundantly produced commodity chemicals because of its importance in the plastics industry, notably for manufacturing polyesters and polyethylene terephthalates. We applied an extended heterogeneous:homogeneous interface, using chloride as a redox mediator at the anode, to facilitate the selective partial oxidation of ethylene to ethylene oxide. We achieved current densities of 1 ampere per square centimeter, Faradaic efficiencies of ~70%, and product specificities of ~97%. When run at 300 milliamperes per square centimeter for 100 hours, the system maintained a 71(±1)% Faradaic efficiency throughout.

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