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 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 ◽  
Catalytic Performance ◽  
Process Performance ◽  
Co2 Utilization ◽  
Faradaic Efficiency ◽  
Co2 Electrolysis ◽  
Reactant Distribution

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...

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.

Ex Situ Characterization Method for Flooding in Gas Diffusion Layers and Membrane Electrode Assemblies With a Hydrophilic Gas Diffusion Layer

2015 ◽  
Vol 12 (6) ◽  
Author(s):  
Toshihiro Tanuma
Keyword(s):  
Catalyst Layer ◽  
Membrane Electrode Assembly ◽  
Gas Diffusion ◽  
Dew Point ◽  
Water Flooding ◽  
Ex Situ ◽  
Membrane Electrode ◽  
Gas Diffusion Layers ◽  
Diffusion Layers ◽  
O2 Concentration

Proper water management is required for the operation of polymer electrolyte fuel cells (PEFCs), in order to maintain the critical balance between adequate membrane hydration and prevention of water flooding in the catalyst layer. In PEFCs, the membrane electrode assembly (MEA) is sandwiched between two gas diffusion layers (GDLs). In addition, a microporous layer (MPL) is generally applied to the GDL substrates for better water removal from the cathode catalyst layer. This paper is the first to report on an ex situ characterization method for water flooding in GDLs. As the humidity of O2 gas on the substrate side of the GDL was increased in incremental steps, O2 gas began to diffuse into the MPL side of the GDL. When the O2 relative humidity exceeded the dew point, water flooding was observed on the surface of the MPL and the O2 concentration dropped sharply because the O2 diffusion was suppressed by the produced liquid water. When comparing to the estimated mass transfer loss based on the actual polarization curves of an MEA using the GDL, it was found that the decrease in the O2 concentration on the MPL side of the GDL can be used as an index of water flooding in the PEFC.

scholarly journals Simulation of the Dynamic Characteristics of a PEMFC System in Fluctuating Operating Conditions

Energies ◽  
2020 ◽  
Vol 13 (14) ◽  
pp. 3596
Author(s):  
Jiangyan Yan ◽  
Chang Zhou ◽  
Zhihai Rong ◽  
Haijiang Wang ◽  
Hui Li ◽  
...  
Keyword(s):  
External Load ◽  
Proton Exchange Membrane ◽  
Membrane Electrode Assembly ◽  
Proton Exchange ◽  
Operating Conditions ◽  
Cathode Side ◽  
Membrane Electrode ◽  
Transient Pressure ◽  
Gas Channel ◽  
Huge Impact

A greater understanding of the dynamic processes inside the stack is urgently needed to optimize the PEMFC (proton exchange membrane fuel cell). In this study, we examined the gas, water and electrochemical processes inside the stack, studied the physical dynamics of system accessories such as gas supplement, flow and pressure-regulating devices, then used Simulink to build a mathematical model of a complete PEMFC system; a segmented testing platform was built to test the spatial distribution of RH (relative humidity) and pressure, which was used to verify the simulation model; based on this model, the complicated phenomena occurring inside the stack during fluctuating operating states were calculated. Our findings showed that the pressure in the gas channel and exhaust manifolds decreased when the external load increased, changing sharply at the moment of load change. The transient pressure difference between the cathode and anode sides (several kPa) had a huge impact on the MEA (membrane electrode assembly); when the load current increased, RH in cathode and cathode channel increased gradually, and the increasing rate of anode side was bigger than that in cathode side. The influence of variance magnitude and change interval of external load were also studied based on the model.

scholarly journals Cation-driven increases in CO2 utilization in a bipolar membrane electrode assembly for CO2 electrolysis

2021 ◽  
Author(s):  
Kailun Yang ◽  
Mengran Li ◽  
Siddhartha Subramanian ◽  
Marijn Blommaert ◽  
Wilson Smith ◽  
...  
Keyword(s):  
Membrane Electrode Assembly ◽  
Membrane Electrode ◽  
Co2 Utilization ◽  
Bipolar Membrane ◽  
Co2 Electrolysis

Stack Compression of PEM Fuel Cells

2004 ◽  
Author(s):  
Yeh-Hung Lai ◽  
Daniel P. Miller ◽  
Chunxin Ji ◽  
Thomas A. Trabold
Keyword(s):  
Fuel Cell ◽  
Membrane Electrode Assembly ◽  
Pem Fuel Cells ◽  
Gas Diffusion ◽  
Membrane Electrode ◽  
Gas Diffusion Layers ◽  
Dimensional Changes ◽  
Diffusion Layers ◽  
Wide Range ◽  
Electrolyte Membranes

The effect of dimensional changes of fuel cell components from temperature and hydration cycles on the stack compression is investigated in this paper. Using a simple spring model including the membrane electrode assembly (MEA), gas diffusion layers (GDL), bipolar plates, seal gaskets, current collectors, insulation plates, end plates, and side plates, we find significant compression changes from 30% over-compression to 23% compression loss from both temperature and humidity changes. The wide range of variation in stack compression is attributed to the swelling behavior of polymer electrolyte membranes, the compression behavior of gas diffusion layers, and the design of stack assembly. This paper also reports the use of finite element method to investigate the compression of MEA and GDL over the channel area where MEA buckling from membrane swelling can result in separation of MEA and GDL. It is suggested that the compression over channels can be improved with higher transverse shear modulus in the GDL in addition to the use of narrower channels. In this paper, we will also discuss the challenges facing the fuel cell manufacturers and component suppliers on the needs for new materials with improved mechanical properties and better testing/modeling techniques to help achieving stable compression and better fuel cell stack designs.

scholarly journals Selective CO-to-acetate electroproduction via intermediate adsorption tuning on ordered Cu-Pd sites

2020 ◽  
Author(s):  
Yali Ji ◽  
Zheng Chen ◽  
Chao Yang ◽  
Yuhang Wang ◽  
Jie Xu ◽  
...  
Keyword(s):  
Active Sites ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Membrane Electrode Assembly ◽  
Membrane Electrode ◽  
Acetate Production ◽  
Faradaic Efficiency ◽  
Potential Alternative ◽  
Acetate Formation ◽  
Pure Cu

Abstract Electrochemical reduction of carbon monoxide (CO) has recently been emerging as a potential alternative for converting carbon emission into high-value multi-carbon products such as acetate. Nonetheless, the activity and selectivity for producing acetate have remained low. Herein, we developed an atomically ordered copper-palladium intermetallic compound (CuPd-IC) structure that achieved a high Faradaic efficiency of 70 ± 5% for CO-to-acetate production with a partial current density of 425 mA·cm− 2. This corresponded to an acetate production rate of 4.0 mmol·h− 1·cm− 2, and 5.3 times of enhancement in acetate production compared to pure Cu. Structural characterizations and density functional theory calculations suggested that CuPd-IC presents a high density of Cu-Pd pairs that act as the active sites to enrich the surface CO coverage, stabilize the surface ethenone as a key acetate-path intermediate, and inhibit hydrogen evolution reaction, thus promoting acetate formation. Using a membrane electrode assembly device, the CuPd-IC catalyst enabled 100 hours of CO-to-acetate operation at 500 mA·cm− 2 and an average acetate Faradaic efficiency of 43%, producing ~ 2 mol acetate.

scholarly journals Cation-Driven Increases of CO2 Utilization in a Bipolar Membrane Electrode Assembly for CO2 Electrolysis

2021 ◽  
pp. 4291-4298
Author(s):  
Kailun Yang ◽  
Mengran Li ◽  
Siddhartha Subramanian ◽  
Marijn A. Blommaert ◽  
Wilson A. Smith ◽  
...  
Keyword(s):  
Membrane Electrode Assembly ◽  
Membrane Electrode ◽  
Co2 Utilization ◽  
Bipolar Membrane ◽  
Co2 Electrolysis
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