scholarly journals The Achilles' heel of iron-based catalysts during oxygen reduction in an acidic medium

2018 ◽  
Vol 11 (11) ◽  
pp. 3176-3182 ◽  
Author(s):  
Chang Hyuck Choi ◽  
Hyung-Kyu Lim ◽  
Min Wook Chung ◽  
Gajeon Chon ◽  
Nastaran Ranjbar Sahraie ◽  
...  
Keyword(s):  
Oxygen Reduction ◽  
Acidic Medium ◽  
Carbon Surface ◽  
Turnover Frequency ◽  
Catalytic Sites ◽  
Iron Based ◽  
Iron Based Catalysts

Exposing Fe–N–C catalysts to H2O2-byproduct leaves their catalytic sites untouched but decreases the turnover frequency via oxidation of the carbon surface.

scholarly journals Achilles' heel of Iron-Based Catalysts During Oxygen Reduction in Acidic Medium

2018 ◽  
Author(s):  
Chang Hyuck Choi ◽  
Hyung-Kyu Lim ◽  
Gajeon Chon ◽  
Min Wook Chung ◽  
Abdulrahman Altin ◽  
...  
Keyword(s):  
Fuel Cells ◽  
Oxygen Reduction ◽  
Acidic Medium ◽  
Active Sites ◽  
Proton Exchange ◽  
Carbon Surface ◽  
Alkaline Electrolyte ◽  
Promising Alternative ◽  
Iron Based ◽  
Deactivation Mechanism

Fuel cells efficiently convert chemical into electric energy, with promising application for clean transportation. In proton-exchange membrane fuel cells (PEMFCs), rare platinum metal catalyzes today the oxygen reduction reaction (ORR) while iron(cobalt)-nitrogen-carbon materials (Fe(Co)-N-C) are a promising alternative. Their active sites can be classified as atomically dispersed metal-ions coordinated to nitrogen atoms (MeNxCy moieties) or nitrogen functionalities (possibly influenced by sub-surface metallic particles). While their durability is a recognized challenge, its rational improvement is impeded by insufficient understanding of operando degradation mechanisms. Here, we show that FeNxCy moieties in a representative Fe-N-C catalyst are structurally stable but electrochemically unstable when exposed in acidic medium to H2O2, the main ORR byproduct. We reveal that exposure to H2O2 leaves iron-based catalytic sites untouched but decreases their turnover frequency (TOF) via oxidation of the carbon surface, leading to weakened O2 binding on iron-based sites. Their TOF is recovered upon electrochemical reduction of the carbon surface, demonstrating the proposed deactivation mechanism. Our results reveal a hitherto unsuspected deactivation mechanism during ORR in acidic medium. This study identifies the N-doped carbon surface as Achilles' heel during ORR catalysis in PEMFCs. Observed in acidic but not in alkaline electrolyte, these insights suggest that durable iron-nitrogen-carbon catalysts are within reach for PEMFCs if rational strategies minimizing the amount of H2O2 or reactive oxygen species (ROS) produced during ORR are developed.

scholarly journals Achilles' heel of Iron-Based Catalysts During Oxygen Reduction in Acidic Medium

2018 ◽  
Author(s):  
Chang Hyuck Choi ◽  
Hyung-Kyu Lim ◽  
Gajeon Chon ◽  
Min Wook Chung ◽  
Abdulrahman Altin ◽  
...  
Keyword(s):  
Fuel Cells ◽  
Oxygen Reduction ◽  
Acidic Medium ◽  
Active Sites ◽  
Proton Exchange ◽  
Carbon Surface ◽  
Alkaline Electrolyte ◽  
Promising Alternative ◽  
Iron Based ◽  
Deactivation Mechanism

Fuel cells efficiently convert chemical into electric energy, with promising application for clean transportation. In proton-exchange membrane fuel cells (PEMFCs), rare platinum metal catalyzes today the oxygen reduction reaction (ORR) while iron(cobalt)-nitrogen-carbon materials (Fe(Co)-N-C) are a promising alternative. Their active sites can be classified as atomically dispersed metal-ions coordinated to nitrogen atoms (MeNxCy moieties) or nitrogen functionalities (possibly influenced by sub-surface metallic particles). While their durability is a recognized challenge, its rational improvement is impeded by insufficient understanding of operando degradation mechanisms. Here, we show that FeNxCy moieties in a representative Fe-N-C catalyst are structurally stable but electrochemically unstable when exposed in acidic medium to H2O2, the main ORR byproduct. We reveal that exposure to H2O2 leaves iron-based catalytic sites untouched but decreases their turnover frequency (TOF) via oxidation of the carbon surface, leading to weakened O2 binding on iron-based sites. Their TOF is recovered upon electrochemical reduction of the carbon surface, demonstrating the proposed deactivation mechanism. Our results reveal a hitherto unsuspected deactivation mechanism during ORR in acidic medium. This study identifies the N-doped carbon surface as Achilles' heel during ORR catalysis in PEMFCs. Observed in acidic but not in alkaline electrolyte, these insights suggest that durable iron-nitrogen-carbon catalysts are within reach for PEMFCs if rational strategies minimizing the amount of H2O2 or reactive oxygen species (ROS) produced during ORR are developed.

Iron-Based Catalysts with Improved Oxygen Reduction Activity in Polymer Electrolyte Fuel Cells

Science ◽  
2009 ◽  
Vol 324 (5923) ◽  
pp. 71-74 ◽  
Author(s):  
Michel Lefèvre ◽  
Eric Proietti ◽  
Frédéric Jaouen ◽  
Jean-Pol Dodelet
Keyword(s):  
Fuel Cells ◽  
Oxygen Reduction ◽  
Polymer Electrolyte ◽  
Polymer Electrolyte Fuel Cells ◽  
Reduction Activity ◽  
Iron Based ◽  
Iron Based Catalysts

scholarly journals Iron based catalysts from novel low-cost organic precursors for enhanced oxygen reduction reaction in neutral media microbial fuel cells

2016 ◽  
Vol 9 (7) ◽  
pp. 2346-2353 ◽  
Author(s):  
Carlo Santoro ◽  
Alexey Serov ◽  
Lydia Stariha ◽  
Mounika Kodali ◽  
Jonathan Gordon ◽  
...  
Keyword(s):  
Fuel Cells ◽  
Oxygen Reduction Reaction ◽  
Oxygen Reduction ◽  
Microbial Fuel Cells ◽  
Low Cost ◽  
Reduction Reaction ◽  
Neutral Media ◽  
Organic Precursors ◽  
Iron Based ◽  
Iron Based Catalysts

Fe-based catalysts based on ricobendazole and niclosamide showed higher performance compared to Pt (20–25%) and AC (90–99%) and more durability in long terms operations.

scholarly journals Single-Atomic Ruthenium Catalytic Sites on Nitrogen-Doped Graphene for Oxygen Reduction Reaction in Acidic Medium

ACS Nano ◽  
2017 ◽  
Vol 11 (7) ◽  
pp. 6930-6941 ◽  
Author(s):  
Chenhao Zhang ◽  
Junwei Sha ◽  
Huilong Fei ◽  
Mingjie Liu ◽  
Sadegh Yazdi ◽  
...  
Keyword(s):  
Oxygen Reduction Reaction ◽  
Oxygen Reduction ◽  
Acidic Medium ◽  
Reduction Reaction ◽  
Nitrogen Doped ◽  
Catalytic Sites ◽  
Nitrogen Doped Graphene ◽  
Doped Graphene

Determination of Iron Active Sites in Pyrolyzed Iron-Based Catalysts for the Oxygen Reduction Reaction

ACS Catalysis ◽  
2012 ◽  
Vol 2 (12) ◽  
pp. 2761-2768 ◽  
Author(s):  
Wenmu Li ◽  
Jason Wu ◽  
Drew C. Higgins ◽  
Ja-Yeon Choi ◽  
Zhongwei Chen
Keyword(s):  
Oxygen Reduction Reaction ◽  
Oxygen Reduction ◽  
Active Sites ◽  
Reduction Reaction ◽  
Iron Based ◽  
Iron Active Sites ◽  
Iron Based Catalysts

Iron-based Catalysts for Oxygen Reduction in PEM Fuel Cells: Expanded Study Using the Pore-filling Method

2019 ◽  
Vol 25 (1) ◽  
pp. 105-115 ◽  
Author(s):  
Michel Lefèvre ◽  
Eric Proietti ◽  
Frederic Jaouen ◽  
Jean-Pol Dodelet
Keyword(s):  
Fuel Cells ◽  
Oxygen Reduction ◽  
Pem Fuel Cells ◽  
Pore Filling ◽  
Filling Method ◽  
Iron Based ◽  
Iron Based Catalysts
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