scholarly journals On the Correlation between the Oxygen in Hydrogen Content and the Catalytic Activity of Cathode Catalysts in PEM Water Electrolysis

2021 ◽  
Author(s):  
Agate Martin ◽  
Patrick Trinke ◽  
Chuyen Van Pham ◽  
Melanie Bühler ◽  
Markus Bierling ◽  
...  
Keyword(s):  
High Surface ◽  
Catalyst Layer ◽  
Linear Sweep Voltammetry ◽  
Water Electrolysis ◽  
Platinum Group Metal ◽  
Reduction Reaction ◽  
Ex Situ ◽  
Recombination Activity ◽  
Cathode Catalysts ◽  
Carbon Based

Abstract Altogether five platinum group metal (PGM) and PGM-free cathode catalysts were investigated in full PEM water electrolysis cells regarding their polarisation behaviour and their hydrogen and oxygen recombination properties. It was shown that the recombination activity of permeated oxygen and evolved hydrogen within the cathodic catalyst layer correlates with the activity of the oxygen reduction reaction (ORR) which was determined ex situ with linear sweep voltammetry. We found that the investigated PGM-free cathode catalysts had a low activity for the ORR resulting in higher measurable oxygen in hydrogen volume fractions compared to the PGM catalysts, which are more active for the ORR. Out of the three investigated PGM-free catalysts, only one commercially available material based on a Ti suboxide showed a similar good polarisation behaviour as the state of the art cathode catalyst platinum, while its recombination activity was the lowest of all catalysts. In addition to the recombination of hydrogen and oxygen on the electrocatalysts, we found that the prevalent carbon-based cathodic porous transport layers (PTL) also offer catalytically active recombination sites. In comparison to an inactive PTL, the measurable oxygen flux using carbon-based PTLs was lower and the recombination was enhanced by microporous coatings with high surface areas.

Mitigation of PtCo/C Cathode Catalyst Degradation via Control of Relative Humidity

2021 ◽  
Author(s):  
Nagappan Ramaswamy ◽  
Swami Kumaraguru ◽  
Ratandeep Singh Kukreja ◽  
Daniel Groom ◽  
Karalee Jarvis ◽  
...  
Keyword(s):  
Relative Humidity ◽  
High Performance ◽  
Proton Exchange Membrane ◽  
Stress Test ◽  
Catalyst Layer ◽  
Reduction Reaction ◽  
Proton Exchange ◽  
Ex Situ ◽  
Primary Power ◽  
Ptco Alloy

Abstract Maintaining the high performance of proton-exchange membrane fuel cells (PEMFC) over the course of its lifetime is a key enabling factor for its successful commercialization as a primary power source in zero-emission transportation applications. In this context, it is important to mitigate the degradation of PtCo-alloy based cathode catalysts used for oxygen reduction reaction (ORR). PtCo-alloy catalysts exhibit high activity at beginning-of-life (BOL) which tends to decrease during operation due to loss of electrochemical surface area (ECSA) and dissolution-contamination related effects of the Co-alloying component. Here, we demonstrate the use of relative humidity (RH) of the inlet gases as a controllable parameter to mitigate the degradation of PtCo-alloy catalyst degradation. We employ a catalyst-specific voltage cycling accelerated stress test (AST) durability protocol as a function of inlet RH to degrade PtCo catalysts. A series of in situ electrochemical diagnostics and ex situ characterizations have been carried out to investigate the catalyst layer characteristics at end-of-test (EOT). Our results show that at sub-saturated conditions of durability protocol operation, PtCo catalyst sustains higher EOT H2/air performance due to better retention of ECSA and smaller impact of Co2+ dissolution/contamination.

Oxygen Reduction Reaction Causes Iron Leaching from Fe-N-C Electrocatalysts

2021 ◽  
Author(s):  
Yu-Ping Ku ◽  
Konrad Ehelebe ◽  
Markus Bierling ◽  
Florian Speck ◽  
Dominik Seeberger ◽  
...  
Keyword(s):  
Oxygen Reduction Reaction ◽  
Oxygen Reduction ◽  
Inductively Coupled Plasma ◽  
Catalyst Layer ◽  
Platinum Group Metal ◽  
Gas Diffusion ◽  
Reduction Reaction ◽  
Alkaline Media ◽  
Inductively Coupled ◽  
Design And Synthesis

Abstract The electrochemical activity of modern Fe-N-C electrocatalysts in alkaline media is on par with that of platinum. For successful application in fuel cells, however, also high durability and longevity must be demonstrated. Currently, design and synthesis of simultaneously active and stable platinum group metal-free electrocatalysts is hindered by a limited understanding of Fe-N-C degradation, especially under operando conditions. In this work, using a gas diffusion electrode half-cell coupled with inductively coupled plasma mass spectrometry setup, Fe dissolution is studied under more realistic conditions, i.e. real catalyst layer and current densities up to 125 mA·cm-2. Varying the rate of oxygen reduction reaction, we show a remarkable correlation between Faradaic electrode charge and Fe dissolution. This finding is rationalized assuming that oxygen reduction and Fe dissolution reactions are interlinked, likely through a common intermediate formed during the Fe3+/Fe2+ redox transitions in coordinated Fe cations. Moreover, such linear correlation allows an introduction and use of a simple metric (stability number). Hence, in the current work, a powerful tool for a more applied stability screening of different electrocatalysts is introduced, which allows on the one hand fast performance investigations under more realistic conditions, and on the other hand more advanced mechanistic understanding of Fe-N-C degradation in catalyst layers.

Hierarchically structured catalyst layer for the oxygen reduction reaction fabricated by electrodeposition of platinum on carbon nanotube coated carbon fiber

RSC Advances ◽  
2015 ◽  
Vol 5 (82) ◽  
pp. 66518-66527 ◽  
Author(s):  
Raghunandan Sharma ◽  
Kamal K. Kar
Keyword(s):  
Active Catalyst ◽  
Catalyst Support ◽  
Catalyst Layer ◽  
Reduction Reaction ◽  
Pt Nanoparticle ◽  
Cathode Catalysts ◽  
Structured Catalyst ◽  
Nanoparticle Clusters ◽  
Fuel Cell Cathode ◽  
Coated Carbon

Hierarchically structured fuel cell cathode catalysts consisting of Pt-nanoparticle clusters coated on a CNT-based, ORR active catalyst support were synthesized.

scholarly journals Effect of carbonate anions on Bi-doped Ca2Ru2O7 pyrochlores that are potential cathode catalysts for low temperature carbonate fuel cells

RSC Advances ◽  
2014 ◽  
Vol 4 (57) ◽  
pp. 30035-30045 ◽  
Author(s):  
Cathryn A. Hancock ◽  
Ai Lien Ong ◽  
John R. Varcoe
Keyword(s):  
Fuel Cells ◽  
Low Temperature ◽  
Oxygen Reduction Reaction ◽  
Oxygen Reduction ◽  
Reduction Reaction ◽  
Electrochemical Study ◽  
Ex Situ ◽  
Cathode Catalysts

This ex situ electrochemical study investigates how the oxygen reduction reaction (ORR) on Bi-doped Ca2Ru2O7 pyrochlore catalysts is affected by the addition of carbonate to the aqueous KOH (1 mol dm−3) electrolyte.

scholarly journals Highly active atomically dispersed CoN4 fuel cell cathode catalysts derived from surfactant-assisted MOFs: carbon-shell confinement strategy

2019 ◽  
Vol 12 (1) ◽  
pp. 250-260 ◽  
Author(s):  
Yanghua He ◽  
Sooyeon Hwang ◽  
David A. Cullen ◽  
M. Aman Uddin ◽  
Lisa Langhorst ◽  
...  
Keyword(s):  
Fuel Cells ◽  
Fuel Cell ◽  
Oxygen Reduction Reaction ◽  
Oxygen Reduction ◽  
Platinum Group Metal ◽  
Reduction Reaction ◽  
Cathode Catalysts ◽  
Highly Active ◽  
Fuel Cell Cathode ◽  
Surfactant Assisted

Platinum group metal (PGM)-free catalysts for oxygen reduction reaction are essential for affordable fuel cells.

scholarly journals Biohybrid Cathode in Single Chamber Microbial Fuel Cell

Nanomaterials ◽  
2018 ◽  
Vol 9 (1) ◽  
pp. 36 ◽  
Author(s):  
Giulia Massaglia ◽  
Isabella Fiorello ◽  
Adriano Sacco ◽  
Valentina Margaria ◽  
Candido Pirri ◽  
...  
Keyword(s):  
Electrochemical Impedance Spectroscopy ◽  
Fuel Cell ◽  
Microbial Fuel Cells ◽  
Electrochemical Impedance ◽  
Linear Sweep Voltammetry ◽  
Power Production ◽  
Reduction Reaction ◽  
Linear Sweep ◽  
Single Chamber ◽  
Carbon Based

The aim of this work is to investigate the properties of biofilms, spontaneously grown on cathode electrodes of single-chamber microbial fuel cells, when used as catalysts for oxygen reduction reaction (ORR). To this purpose, a comparison between two sets of different carbon-based cathode electrodes is carried out. The first one (Pt-based biocathode) is based on the proliferation of the biofilm onto a Pt/C layer, leading thus to the creation of a biohybrid catalyst. The second set of electrodes (Pt-free biocathode) is based on a bare carbon-based material, on which biofilm grows and acts as the sole catalyst for ORR. Linear sweep voltammetry (LSV) characterization confirmed better performance when the biofilm is formed on both Pt-based and Pt-free cathodes, with respect to that obtained by biofilm-free cathodes. To analyze the properties of spontaneously grown cathodic biofilms on carbon-based electrodes, electrochemical impedance spectroscopy is employed. This study demonstrates that the highest power production is reached when aerobic biofilm acts as a catalyst for ORR in synergy with Pt in the biohybrid cathode.

scholarly journals Structure of Active Sites of Fe-N-C Nano-Catalysts for Alkaline Exchange Membrane Fuel Cells

Nanomaterials ◽  
2018 ◽  
Vol 8 (12) ◽  
pp. 965 ◽  
Author(s):  
Hirofumi Kishi ◽  
Tomokazu Sakamoto ◽  
Koichiro Asazawa ◽  
Susumu Yamaguchi ◽  
Takeshi Kato ◽  
...  
Keyword(s):  
Active Sites ◽  
Density Functional ◽  
Carbon Nanomaterials ◽  
Catalyst Activity ◽  
Platinum Group Metal ◽  
Reduction Reaction ◽  
Ex Situ ◽  
Metallic Particles ◽  
Theoretical Approaches ◽  
Nano Catalysts

Platinum group metal-free (PGM-free) catalysts based on transition metal-nitrogen-carbon nanomaterials have been studied by a combination of ex situ and in situ synchrotron X-ray spectroscopy techniques; high-resolution Transmission Electron Microscope (TEM); Mößbauer spectroscopy combined with electrochemical methods and Density Functional Theory (DFT) modeling/theoretical approaches. The main objective of this study was to correlate the HO2− generation with the chemical nature and surface availability of active sites in iron-nitrogen-carbon (Fe-N-C) catalysts derived by sacrificial support method (SSM). These nanomaterials present a carbonaceous matrix with nitrogen-doped sites and atomically dispersed and; in some cases; iron and nanoparticles embedded in the carbonaceous matrix. Fe-N-C oxygen reduction reaction electrocatalysts were synthesized by varying several synthetic parameters to obtain nanomaterials with different composition and morphology. Combining spectroscopy, microscopy and electrochemical reactivity allowed the building of structure-to-properties correlations which demonstrate the contributions of these moieties to the catalyst activity, and mechanistically assign the active sites to individual reaction steps. Associated with Fe-Nx motive and the presence of Fe metallic particles in the electrocatalysts showed the clear differences in the variation of composition; processing and treatment conditions of SSM. From the results of material characterization; catalytic activity and theoretical studies; Fe metallic particles (coated with carbon) are main contributors into the HO2− generation.

Graphene Supported Tungsten Carbide as Catalyst for Electrochemical Reduction of CO2

2019 ◽  
Author(s):  
Sahithi Ananthaneni ◽  
Rees Rankin
Keyword(s):  
Tungsten Carbide ◽  
Electrochemical Reduction ◽  
Low Cost ◽  
Co2 Reduction ◽  
Platinum Group Metal ◽  
Reduction Reaction ◽  
Metal Carbides ◽  
Depth Study ◽  
Reduction Of Co2 ◽  
Co2 Reduction Reaction

<div>Electrochemical reduction of CO2 to useful chemical and fuels in an energy efficient way is currently an expensive and inefficient process. Recently, low-cost transition metal-carbides (TMCs) are proven to exhibit similar electronic structure similarities to Platinum-Group-Metal (PGM) catalysts and hence can be good substitutes for some important reduction reactions. In this work, we test graphenesupported WC (Tungsten Carbide) nanocluster as an electrocatalyst for the CO2 reduction reaction. Specifically, we perform DFT studies to understand various possible reaction mechanisms and determine the lowest thermodynamic energy landscape of CO2 reduction to various products such as CO, HCOOH, CH3OH, and CH4. This in-depth study of reaction energetics could lead to improvements and develop more efficient electrocatalysts for CO2 reduction.<br></div>

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