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Plamen Atanassov - One of the best experts on this subject based on the ideXlab platform.
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establishing reactivity descriptors for Platinum Group Metal pgm free fe n c catalysts for pem fuel cells
Energy and Environmental Science, 2020Co-Authors: Mathias Primbs, Plamen Atanassov, Moulay Tahar Sougrati, Daniel Malko, Asad Mehmood, Pierreyves Blanchard, Gaetano Granozzi, Tomasz Kosmala, Giorgia Daniel, Jonathon SharmanAbstract:We report a comprehensive analysis of the catalytic oxygen reduction reaction (ORR) reactivity of four of today’s most active benchmark Platinum Group Metal-free (PGM-free) iron/nitrogen doped carbon electrocatalysts (Fe-N-Cs). Our analysis reaches far beyond previous such attempts in linking kinetic performance metrics, such as electrocatalytic mass-based and surface area-based catalytic activity with previously elusive kinetic metrics such as the active Metal site density (SD) and the catalytic turnover frequency (TOF). Kinetic ORR activities, SD and TOF values were evaluated using in-situ electrochemical NO2- reduction as well as an ex-situ gaseous CO cryo chemisorption. Experimental ex-situ and in-situ Fe surface site densities displayed remarkable quantitative congruence. Plots of SD versus TOF (“reactivity maps”) are utilized as new analytical tools to deconvolute ORR reactivities and thus enabling rational catalyst developments. A microporous catalyst showed large SD values paired with low TOF, while mesoporous catalysts displayed the opposite. Trends in Fe surface site density were linked to molecular nitrogen and Fe moieties (D1 and D2 from 57Fe Mossbauer spectroscopy), from which pore locations of catalytically active D1 and D2 sites were established. This cross-laboratory analysis, its employed experimental practices and analytical methodologies are expected to serve as a widely accepted reference for future, knowledge-based research into improved PGM-free fuel cell cathode catalysts.
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Nitrogen-Doped Graphene Oxide Electrocatalysts for the Oxygen Reduction Reaction
ACS Applied Nano Materials, 2019Co-Authors: Joseph H. Dumont, Ulises Martinez, Geraldine M Purdy, Andrew M. Dattelbaum, Piotr Zelenay, Plamen Atanassov, Kateryna Artyushkova, Aditya D. Mohite, Gautam GuptaAbstract:Platinum Group Metal-free (PGM-free) electrocatalysts for the oxygen reduction reaction (ORR) often exhibit a complex functionalized graphitic structure. Because of this complex structure, limited ...
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direct observations of liquid water formation at nano and micro scale in Platinum Group Metal free electrodes by operando x ray computed tomography
Materials Today Energy, 2018Co-Authors: Stanley J Normile, Plamen Atanassov, Alexey Serov, Xianghui Xiao, Vincent De Andrade, Dinesh C Sabarirajan, Pratiti Mandal, Osvaldo Calzada, Dilworth Y Parkinson, Iryna V ZenyukAbstract:Abstract Platinum Group Metal (PGM)-free catalyst materials are promising alternatives to Platinum-based catalysts for use in polymer electrolyte fuel cells (PEFCs). The reduced cost and abundancy of the PGM-free catalyst materials can be potentially transformative. Catalytic activity, associated with atomically dispersed transition Metal active sites, is intimately linked with the emerging morphology of the carbonaceous graphene-like material at nano-scale. Optimizing the morphology of these PGM-free catalyst layers for enhanced transport properties at the nano and micro-scales is critical for achieving overall performance, expressed as power-density, needed to make such materials technologically attractive. Unfortunately, the current understandings of both morphology and transport processes are very limited due to the novelty of the materials and the challenges in designing operando characterization techniques. In order to bridge these gaps in understanding, we used operando synchrotron X-ray computed tomography to visualize water transport in operating PEFCs. We found that liquid water pooled at the components interfaces and within larger catalyst layer voids. In the smaller macro-pores, ionomer swelling was observed under humidified conditions with nano X-ray computed tomography. These previously unknown insights will provide guidance on electrode and interface design to improve water management and power density of the PEFC with cost-effective PGM-free electrocatalysts.
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iron nicarbazin derived Platinum Group Metal free electrocatalyst in scalable size air breathing cathodes for microbial fuel cells
Electrochimica Acta, 2018Co-Authors: Benjamin Erable, Carlo Santoro, Mounika Kodali, Alexey Serov, Manon Oliot, Remy Lacroix, Alain Bergel, Plamen AtanassovAbstract:In this work, a Platinum Group Metal-free (PGM-free) catalyst based on iron as transitional Metal and Nicarbazin (NCB) as low cost organic precursor was synthesized using Sacrificial Support Method (SSM). The catalyst was then incorporated into a large area air-breathing cathode fabricated by pressing with a large diameter pellet die. The electrochemical tests in abiotic conditions revealed that after a couple of weeks of successful operation, the electrode experienced drop in performances in reason of electrolyte leakage, which was not an issue with the smaller electrodes. A decrease in the hydrophobic properties over time and a consequent cathode flooding was suspected to be the cause. On the other side, in the present work, for the first time, it was demonstrated the proof of principle and provided initial guidance for manufacturing MFC electrodes with large geometric areas. The tests in MFCs showed a maximum power density of 1.85 W m−2. The MFCs performances due to the addition of Fe-NCB were much higher compared to the iron-free material. A numerical model using Nernst-Monod and Butler-Volmer equations were used to predict the effect of electrolyte solution conductivity and distance anode-cathode on the overall MFC power output. Considering the existing conditions, the higher overall power predicted was 3.6 mW at 22.2 S m−1 and at inter-electrode distance of 1 cm.
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effect of ph on the activity of Platinum Group Metal free catalysts in oxygen reduction reaction
ACS Catalysis, 2018Co-Authors: Santiago Rojascarbonell, Carlo Santoro, Kateryna Artyushkova, Alexey Serov, Ivana Matanovic, Plamen AtanassovAbstract:The impact of the electrolyte’s pH on the catalytic activity of Platinum Group Metal-free (PGM-free) catalysts toward the oxygen reduction reaction (ORR) was studied. The results indicate that the ORR mechanism is determined by the affinity of protons and hydroxyls toward multiple functional Groups present on the surface of the PGM-free catalyst. It was shown that the ORR is limited by the proton-coupled electron transfer at pH values below 10.5. At higher pH values (>10.5), the reaction occurs in the outer Helmholtz plane (OHP), favoring hydrogen peroxide production. Using a novel approach, the changes in the surface chemistry of PGM-free catalyst in a full pH range were studied by X-ray photoelectron spectroscopy (XPS). The variations in the surface concentration of nitrogen and carbon species are correlated with the electron transfer process and overall kinetics. This study establishes the critical role of the multitude of surface functional Groups, presented as moieties or defects in the carbonaceous ...
Kateryna Artyushkova - One of the best experts on this subject based on the ideXlab platform.
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Nitrogen-Doped Graphene Oxide Electrocatalysts for the Oxygen Reduction Reaction
ACS Applied Nano Materials, 2019Co-Authors: Joseph H. Dumont, Ulises Martinez, Geraldine M Purdy, Andrew M. Dattelbaum, Piotr Zelenay, Plamen Atanassov, Kateryna Artyushkova, Aditya D. Mohite, Gautam GuptaAbstract:Platinum Group Metal-free (PGM-free) electrocatalysts for the oxygen reduction reaction (ORR) often exhibit a complex functionalized graphitic structure. Because of this complex structure, limited ...
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effect of ph on the activity of Platinum Group Metal free catalysts in oxygen reduction reaction
ACS Catalysis, 2018Co-Authors: Santiago Rojascarbonell, Carlo Santoro, Kateryna Artyushkova, Alexey Serov, Ivana Matanovic, Plamen AtanassovAbstract:The impact of the electrolyte’s pH on the catalytic activity of Platinum Group Metal-free (PGM-free) catalysts toward the oxygen reduction reaction (ORR) was studied. The results indicate that the ORR mechanism is determined by the affinity of protons and hydroxyls toward multiple functional Groups present on the surface of the PGM-free catalyst. It was shown that the ORR is limited by the proton-coupled electron transfer at pH values below 10.5. At higher pH values (>10.5), the reaction occurs in the outer Helmholtz plane (OHP), favoring hydrogen peroxide production. Using a novel approach, the changes in the surface chemistry of PGM-free catalyst in a full pH range were studied by X-ray photoelectron spectroscopy (XPS). The variations in the surface concentration of nitrogen and carbon species are correlated with the electron transfer process and overall kinetics. This study establishes the critical role of the multitude of surface functional Groups, presented as moieties or defects in the carbonaceous ...
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influence of Platinum Group Metal free catalyst synthesis on microbial fuel cell performance
Journal of Power Sources, 2018Co-Authors: Carlo Santoro, Kateryna Artyushkova, Santiago Rojascarbonell, Roxanne Awais, Rohan Gokhale, Mounika Kodali, Alexey Serov, Plamen AtanassovAbstract:Abstract Platinum Group Metal-free (PGM-free) ORR catalysts from the Fe-N-C family were synthesized using sacrificial support method (SSM) technique. Six experimental steps were used during the synthesis: 1) mixing the precursor, the Metal salt, and the silica template; 2) first pyrolysis in hydrogen rich atmosphere; 3) ball milling; 4) etching the silica template using harsh acids environment; 5) the second pyrolysis in ammonia rich atmosphere; 6) final ball milling. Three independent batches were fabricated following the same procedure. The effect of each synthetic parameters on the surface chemistry and the electrocatalytic performance in neutral media was studied. Rotating ring disk electrode (RRDE) experiment showed an increase in half wave potential and limiting current after the pyrolysis steps. The additional improvement was observed after etching and performing the second pyrolysis. A similar trend was seen in microbial fuel cells (MFCs), in which the power output increased from 167 ± 2 μW cm −2 to 214 ± 5 μW cm −2 . X-ray Photoelectron Spectroscopy (XPS) was used to evaluate surface chemistry of catalysts obtained after each synthetic step. The changes in chemical composition were directly correlated with the improvements in performance. We report outstanding reproducibility in both composition and performance among the three different batches.
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Platinum Group Metal free nimo hydrogen oxidation catalysts high performance and durability in alkaline exchange membrane fuel cells
Journal of Materials Chemistry, 2017Co-Authors: Sadia Kabir, Kateryna Artyushkova, Kenneth Lemire, Madeleine Odgaard, Debbie Schlueter, Alexandr G Oshchepkov, Antoine Bonnefont, Elena R Savinova, Dinesh C Sabarirajan, Pratiti MandalAbstract:We introduce a new Platinum Group Metal-free (PGM-free) hydrogen oxidation electrocatalyst with superior performance in anodes of alkaline exchange membrane fuel cells (AEMFCs). A carbon-supported biMetallic nickel–molybdenum catalyst was synthesized by thermal reduction of transition Metal precursors on the surface of a carbon support (KetjenBlack 600J). The mass-weighted activity of 4.5 A gMe−1 determined in a liquid electrolyte 0.1 M NaOH using a rotating disk electrode (RDE) technique is comparable to the value reported for Pd/C with a comparable particle size under similar conditions. This NiMo/KB catalyst was integrated in a membrane electrode assembly (MEA) using an alkaline exchange membrane and ionomer. Single AEMFC tests performed in a H2/O2 configuration resulted in a record power density output of 120 mW cm−2 at 0.5 V, the MEA was found to be durable under the conditions of potential hold of 0.7 V for 115 h. For the first time, operando X-ray computed tomography (CT) experiments were performed demonstrating liquid water formation at the PGM-free anode during cell operation, and in situ ambient pressure X-ray photoelectron spectroscopy (APXPS) and X-ray absorption spectroscopy (APXAS) were used to study the role of molybdenum in hydrogen adsorption.
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nano structured Platinum Group Metal free catalysts and their integration in fuel cell electrode architectures
Applied Catalysis B-environmental, 2017Co-Authors: Alexey Serov, Kateryna Artyushkova, Andrew Shum, Xianghui Xiao, Vincent De Andrade, Iryna V Zenyuk, Plamen AtanassovAbstract:Abstract The novel Platinum Group Metal-free (PGM-free) catalyst for the oxygen reduction reaction (ORR) is synthesized by a modified sacrificial support method (SSM). The catalyst chemical/surface composition is studied by X-ray photoelectron spectroscopy, and the morphology of the material is observed using both HR-SEM and HR-TEM, demonstrating the open-frame, self-supported catalysts. This new catalyst’s electrochemical performance is evaluated by polarization curves and has behaviour comparable to the state-of-the-art PGM-free catalysts. Meso-structure imaging shows pores on the order of 100 nm, the mean size of the individual silica particles in the sacrificial support. For the first time, PGM-free catalyst layer (CL) morphology in a membrane electrode assembly (MEA) is studied in detail by combined nano- and micro X-ray computed tomography (CT) and interpretational modelling. The highly inhomogeneous, high-tortuosity, through-thickness structure of the CL is observed with micro-CT. The nano-CT method for these thick PGM-free electrodes is not sufficient to capture the full through-thickness morphology of these electrodes. Water retention curves suggest water pooling at the MEA components’ interfaces and significant dependence of capilary pressure and saturation on through-thickness location. This study is the first of its kind to identify morphology-dependent transport losses in the thick PGM-free electrodes using scale-bridging between meso-, micro-, and macro.
Alexey Serov - One of the best experts on this subject based on the ideXlab platform.
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direct observations of liquid water formation at nano and micro scale in Platinum Group Metal free electrodes by operando x ray computed tomography
Materials Today Energy, 2018Co-Authors: Stanley J Normile, Plamen Atanassov, Alexey Serov, Xianghui Xiao, Vincent De Andrade, Dinesh C Sabarirajan, Pratiti Mandal, Osvaldo Calzada, Dilworth Y Parkinson, Iryna V ZenyukAbstract:Abstract Platinum Group Metal (PGM)-free catalyst materials are promising alternatives to Platinum-based catalysts for use in polymer electrolyte fuel cells (PEFCs). The reduced cost and abundancy of the PGM-free catalyst materials can be potentially transformative. Catalytic activity, associated with atomically dispersed transition Metal active sites, is intimately linked with the emerging morphology of the carbonaceous graphene-like material at nano-scale. Optimizing the morphology of these PGM-free catalyst layers for enhanced transport properties at the nano and micro-scales is critical for achieving overall performance, expressed as power-density, needed to make such materials technologically attractive. Unfortunately, the current understandings of both morphology and transport processes are very limited due to the novelty of the materials and the challenges in designing operando characterization techniques. In order to bridge these gaps in understanding, we used operando synchrotron X-ray computed tomography to visualize water transport in operating PEFCs. We found that liquid water pooled at the components interfaces and within larger catalyst layer voids. In the smaller macro-pores, ionomer swelling was observed under humidified conditions with nano X-ray computed tomography. These previously unknown insights will provide guidance on electrode and interface design to improve water management and power density of the PEFC with cost-effective PGM-free electrocatalysts.
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iron nicarbazin derived Platinum Group Metal free electrocatalyst in scalable size air breathing cathodes for microbial fuel cells
Electrochimica Acta, 2018Co-Authors: Benjamin Erable, Carlo Santoro, Mounika Kodali, Alexey Serov, Manon Oliot, Remy Lacroix, Alain Bergel, Plamen AtanassovAbstract:In this work, a Platinum Group Metal-free (PGM-free) catalyst based on iron as transitional Metal and Nicarbazin (NCB) as low cost organic precursor was synthesized using Sacrificial Support Method (SSM). The catalyst was then incorporated into a large area air-breathing cathode fabricated by pressing with a large diameter pellet die. The electrochemical tests in abiotic conditions revealed that after a couple of weeks of successful operation, the electrode experienced drop in performances in reason of electrolyte leakage, which was not an issue with the smaller electrodes. A decrease in the hydrophobic properties over time and a consequent cathode flooding was suspected to be the cause. On the other side, in the present work, for the first time, it was demonstrated the proof of principle and provided initial guidance for manufacturing MFC electrodes with large geometric areas. The tests in MFCs showed a maximum power density of 1.85 W m−2. The MFCs performances due to the addition of Fe-NCB were much higher compared to the iron-free material. A numerical model using Nernst-Monod and Butler-Volmer equations were used to predict the effect of electrolyte solution conductivity and distance anode-cathode on the overall MFC power output. Considering the existing conditions, the higher overall power predicted was 3.6 mW at 22.2 S m−1 and at inter-electrode distance of 1 cm.
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effect of ph on the activity of Platinum Group Metal free catalysts in oxygen reduction reaction
ACS Catalysis, 2018Co-Authors: Santiago Rojascarbonell, Carlo Santoro, Kateryna Artyushkova, Alexey Serov, Ivana Matanovic, Plamen AtanassovAbstract:The impact of the electrolyte’s pH on the catalytic activity of Platinum Group Metal-free (PGM-free) catalysts toward the oxygen reduction reaction (ORR) was studied. The results indicate that the ORR mechanism is determined by the affinity of protons and hydroxyls toward multiple functional Groups present on the surface of the PGM-free catalyst. It was shown that the ORR is limited by the proton-coupled electron transfer at pH values below 10.5. At higher pH values (>10.5), the reaction occurs in the outer Helmholtz plane (OHP), favoring hydrogen peroxide production. Using a novel approach, the changes in the surface chemistry of PGM-free catalyst in a full pH range were studied by X-ray photoelectron spectroscopy (XPS). The variations in the surface concentration of nitrogen and carbon species are correlated with the electron transfer process and overall kinetics. This study establishes the critical role of the multitude of surface functional Groups, presented as moieties or defects in the carbonaceous ...
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power generation in microbial fuel cells using Platinum Group Metal free cathode catalyst effect of the catalyst loading on performance and costs
Journal of Power Sources, 2018Co-Authors: Carlo Santoro, Mounika Kodali, Alexey Serov, Sergio Herrera, Ioannis Ieropoulos, Plamen AtanassovAbstract:Abstract Platinum Group Metal-free (PGM-free) catalyst with different loadings was investigated in air breathing electrodes microbial fuel cells (MFCs). Firstly, the electrocatalytic activity towards oxygen reduction reaction (ORR) of the catalyst was investigated by rotating ring disk electrode (RRDE) setup with different catalyst loadings. The results showed that higher loading led to an increased in the half wave potential and the limiting current and to a further decrease in the peroxide production. The electrons transferred also slightly increased with the catalyst loading up to the value of ≈3.75. This variation probably indicates that the catalyst investigated follow a 2x2e − transfer mechanism. The catalyst was integrated within activated carbon pellet-like air-breathing cathode in eight different loadings varying between 0.1 mgcm −2 and 10 mgcm −2 . Performance were enhanced gradually with the increase in catalyst content. Power densities varied between 90 ± 9 μWcm −2 and 262 ± 4 μWcm −2 with catalyst loading of 0.1 mgcm −2 and 10 mgcm −2 respectively. Cost assessments related to the catalyst performance are presented. An increase in catalyst utilization led to an increase in power generated with a substantial increase in the whole costs. Also a decrease in performance due to cathode/catalyst deterioration over time led to a further increase in the costs.
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influence of Platinum Group Metal free catalyst synthesis on microbial fuel cell performance
Journal of Power Sources, 2018Co-Authors: Carlo Santoro, Kateryna Artyushkova, Santiago Rojascarbonell, Roxanne Awais, Rohan Gokhale, Mounika Kodali, Alexey Serov, Plamen AtanassovAbstract:Abstract Platinum Group Metal-free (PGM-free) ORR catalysts from the Fe-N-C family were synthesized using sacrificial support method (SSM) technique. Six experimental steps were used during the synthesis: 1) mixing the precursor, the Metal salt, and the silica template; 2) first pyrolysis in hydrogen rich atmosphere; 3) ball milling; 4) etching the silica template using harsh acids environment; 5) the second pyrolysis in ammonia rich atmosphere; 6) final ball milling. Three independent batches were fabricated following the same procedure. The effect of each synthetic parameters on the surface chemistry and the electrocatalytic performance in neutral media was studied. Rotating ring disk electrode (RRDE) experiment showed an increase in half wave potential and limiting current after the pyrolysis steps. The additional improvement was observed after etching and performing the second pyrolysis. A similar trend was seen in microbial fuel cells (MFCs), in which the power output increased from 167 ± 2 μW cm −2 to 214 ± 5 μW cm −2 . X-ray Photoelectron Spectroscopy (XPS) was used to evaluate surface chemistry of catalysts obtained after each synthetic step. The changes in chemical composition were directly correlated with the improvements in performance. We report outstanding reproducibility in both composition and performance among the three different batches.
Carlo Santoro - One of the best experts on this subject based on the ideXlab platform.
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iron nicarbazin derived Platinum Group Metal free electrocatalyst in scalable size air breathing cathodes for microbial fuel cells
Electrochimica Acta, 2018Co-Authors: Benjamin Erable, Carlo Santoro, Mounika Kodali, Alexey Serov, Manon Oliot, Remy Lacroix, Alain Bergel, Plamen AtanassovAbstract:In this work, a Platinum Group Metal-free (PGM-free) catalyst based on iron as transitional Metal and Nicarbazin (NCB) as low cost organic precursor was synthesized using Sacrificial Support Method (SSM). The catalyst was then incorporated into a large area air-breathing cathode fabricated by pressing with a large diameter pellet die. The electrochemical tests in abiotic conditions revealed that after a couple of weeks of successful operation, the electrode experienced drop in performances in reason of electrolyte leakage, which was not an issue with the smaller electrodes. A decrease in the hydrophobic properties over time and a consequent cathode flooding was suspected to be the cause. On the other side, in the present work, for the first time, it was demonstrated the proof of principle and provided initial guidance for manufacturing MFC electrodes with large geometric areas. The tests in MFCs showed a maximum power density of 1.85 W m−2. The MFCs performances due to the addition of Fe-NCB were much higher compared to the iron-free material. A numerical model using Nernst-Monod and Butler-Volmer equations were used to predict the effect of electrolyte solution conductivity and distance anode-cathode on the overall MFC power output. Considering the existing conditions, the higher overall power predicted was 3.6 mW at 22.2 S m−1 and at inter-electrode distance of 1 cm.
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effect of ph on the activity of Platinum Group Metal free catalysts in oxygen reduction reaction
ACS Catalysis, 2018Co-Authors: Santiago Rojascarbonell, Carlo Santoro, Kateryna Artyushkova, Alexey Serov, Ivana Matanovic, Plamen AtanassovAbstract:The impact of the electrolyte’s pH on the catalytic activity of Platinum Group Metal-free (PGM-free) catalysts toward the oxygen reduction reaction (ORR) was studied. The results indicate that the ORR mechanism is determined by the affinity of protons and hydroxyls toward multiple functional Groups present on the surface of the PGM-free catalyst. It was shown that the ORR is limited by the proton-coupled electron transfer at pH values below 10.5. At higher pH values (>10.5), the reaction occurs in the outer Helmholtz plane (OHP), favoring hydrogen peroxide production. Using a novel approach, the changes in the surface chemistry of PGM-free catalyst in a full pH range were studied by X-ray photoelectron spectroscopy (XPS). The variations in the surface concentration of nitrogen and carbon species are correlated with the electron transfer process and overall kinetics. This study establishes the critical role of the multitude of surface functional Groups, presented as moieties or defects in the carbonaceous ...
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power generation in microbial fuel cells using Platinum Group Metal free cathode catalyst effect of the catalyst loading on performance and costs
Journal of Power Sources, 2018Co-Authors: Carlo Santoro, Mounika Kodali, Alexey Serov, Sergio Herrera, Ioannis Ieropoulos, Plamen AtanassovAbstract:Abstract Platinum Group Metal-free (PGM-free) catalyst with different loadings was investigated in air breathing electrodes microbial fuel cells (MFCs). Firstly, the electrocatalytic activity towards oxygen reduction reaction (ORR) of the catalyst was investigated by rotating ring disk electrode (RRDE) setup with different catalyst loadings. The results showed that higher loading led to an increased in the half wave potential and the limiting current and to a further decrease in the peroxide production. The electrons transferred also slightly increased with the catalyst loading up to the value of ≈3.75. This variation probably indicates that the catalyst investigated follow a 2x2e − transfer mechanism. The catalyst was integrated within activated carbon pellet-like air-breathing cathode in eight different loadings varying between 0.1 mgcm −2 and 10 mgcm −2 . Performance were enhanced gradually with the increase in catalyst content. Power densities varied between 90 ± 9 μWcm −2 and 262 ± 4 μWcm −2 with catalyst loading of 0.1 mgcm −2 and 10 mgcm −2 respectively. Cost assessments related to the catalyst performance are presented. An increase in catalyst utilization led to an increase in power generated with a substantial increase in the whole costs. Also a decrease in performance due to cathode/catalyst deterioration over time led to a further increase in the costs.
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influence of Platinum Group Metal free catalyst synthesis on microbial fuel cell performance
Journal of Power Sources, 2018Co-Authors: Carlo Santoro, Kateryna Artyushkova, Santiago Rojascarbonell, Roxanne Awais, Rohan Gokhale, Mounika Kodali, Alexey Serov, Plamen AtanassovAbstract:Abstract Platinum Group Metal-free (PGM-free) ORR catalysts from the Fe-N-C family were synthesized using sacrificial support method (SSM) technique. Six experimental steps were used during the synthesis: 1) mixing the precursor, the Metal salt, and the silica template; 2) first pyrolysis in hydrogen rich atmosphere; 3) ball milling; 4) etching the silica template using harsh acids environment; 5) the second pyrolysis in ammonia rich atmosphere; 6) final ball milling. Three independent batches were fabricated following the same procedure. The effect of each synthetic parameters on the surface chemistry and the electrocatalytic performance in neutral media was studied. Rotating ring disk electrode (RRDE) experiment showed an increase in half wave potential and limiting current after the pyrolysis steps. The additional improvement was observed after etching and performing the second pyrolysis. A similar trend was seen in microbial fuel cells (MFCs), in which the power output increased from 167 ± 2 μW cm −2 to 214 ± 5 μW cm −2 . X-ray Photoelectron Spectroscopy (XPS) was used to evaluate surface chemistry of catalysts obtained after each synthetic step. The changes in chemical composition were directly correlated with the improvements in performance. We report outstanding reproducibility in both composition and performance among the three different batches.
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biMetallic Platinum Group Metal free catalysts for high power generating microbial fuel cells
Journal of Power Sources, 2017Co-Authors: Mounika Kodali, Carlo Santoro, Alexey Serov, Sergio Herrera, Plamen AtanassovAbstract:Abstract M1-M2-N-C biMetallic catalysts with M1 as Fe and Co and M2 as Fe, Co, Ni and Mn were synthesized and investigated as cathode catalysts for oxygen reduction reaction (ORR). The catalysts were prepared by Sacrificial Support Method in which silica was the template and aminoantipyrine (AAPyr) was the organic precursor. The electro-catalytic properties of these catalysts were investigated by using rotating ring disk (RRDE) electrode setup in neutral electrolyte. Fe-Mn-AAPyr outperformed Fe-AAPyr that showed higher performances compared to Fe-Co-AAPyr and Fe-Ni-AAPyr in terms of half-wave potential. In parallel, Fe-Co-AAPyr, Co-Mn-AAPyr and Co-Ni-AAPyr outperformed Co-AAPyr. The presence of Co within the catalyst contributed to high peroxide production not desired for efficient ORR. The catalytic capability of the catalysts integrated in air-breathing cathode was also verified. It was found that Co-based catalysts showed an improvement in performance by the addition of second Metal compared to simple Co- AAPyr. Fe-based biMetallic materials didn't show improvement compared to Fe-AAPyr with the exception of Fe-Mn-AAPyr catalyst that had the highest performance recorded in this study with maximum power density of 221.8 ± 6.6 μWcm −2 . Activated carbon (AC) was used as control and had the lowest performances in RRDE and achieved only 95.6 ± 5.8 μWcm −2 when tested in MFC.
Hailian Tang - One of the best experts on this subject based on the ideXlab platform.
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oxidative strong Metal support interactions omsi of supported Platinum Group Metal catalysts
Chemical Science, 2018Co-Authors: Hailian Tang, Yang Su, Leilei Zhang, Tianbo Li, Ketao Zang, Lin Li, Botao Qiao, Junhu WangAbstract:Supported Platinum-Group Metal (PGM) catalysts are widely used in many important industrial processes. Metal–support interaction is of great importance in tailoring their catalytic performance. Here, we report the first example of oxidative strong Metal–support interactions (OMSIs) between PGM and hydroxyapatite (HAP) which can be extended to PGM and ZnO. It occurred under high-temperature oxidation conditions accompanied by the encapsulation of PGM by HAP and electron transfer between PGM and HAP. With this OMSI, the aggregation and leaching of PGMs were significantly inhibited, resulting in an excellent catalytic stability and much improved reusability of supported Pt and Pd catalysts, respectively. This is the first time to find that PGMs can manifest OMSI which benefits the stabilization of PGM catalysts under oxidative reaction conditions. This new type of SMSI not only contributed to a deeper understanding of SMSI but also provided a new way to develop new stable PGM catalysts.