Journal of the Chemical Society, Faraday Transactions, 1996
Galvanostatic pulse and pulse reverse techniques have been used to study the plating of zinc-nick... more Galvanostatic pulse and pulse reverse techniques have been used to study the plating of zinc-nickel alloys in the presence of nonyl phenyl polyethylene oxide. The effects of average current density, rotation speed of disc electrode and the presence of nonyl phenyl polyethylene oxide in the electrolyte on deposition of zinc-nickel alloys were evaluated. Zinc-nickel plating bath solution chemistry was studied by determining the equilibrium concentrations at various pH levels. It was found that the alloy composition was determined by solution equilibria, mass transfer of the electroactive species within the diffusion layer and by the surface coverage of nonyl phenyl polyethylene oxide.
Cobalt coatings on metal hydrides give rise to an additional capacity due to the cobalt on the su... more Cobalt coatings on metal hydrides give rise to an additional capacity due to the cobalt on the surface of the alloy. In such a case, the galvanostatic discharge technique cannot be used to measure the diffusion coefficient of hydrogen in the alloy. We present here an analytical ...
Characterization of Sol-Gel-Derived Cobalt Oxide Xerogels as Electrochemical Capacitors.-Very fin... more Characterization of Sol-Gel-Derived Cobalt Oxide Xerogels as Electrochemical Capacitors.-Very fine cobalt oxide xerogel powders are prepared from CoCl 2 by use of a unique solution chemistry associated with the sol-gel process. Thermal treatment has significant effects on the surface area, pore volume, crystallinity, particle structure, and corresponding electrochemical properties. The highest average specific capacitance obtained is 291 F/g for a single electrode, and it corresponds to the CoOx xerogel electrode calcined at 150
Introduction: The superior power density feature of electrochemical double layer capacitors (desp... more Introduction: The superior power density feature of electrochemical double layer capacitors (despite its poor energy density) and the remarkably high energy density property of advanced batteries (despite its poor power density) presents an excellent case for the optimization of energy and power density by the combination of advanced battery systems and high surface area electrochemical double layer capacitors (commonly referred to as the hybrid systems). Several research attempts has been made on hybrid systems which exhibit extended run time and enhanced power capability of hybrid systems as against the battery alone systems. The optimization of these hybrid systems requires extensive experimental effort and so sophisticated models predicting the behavior of hybrid systems could be useful for determining optimization strategies. A model predicting the performance of a lithium-ion battery/electrochemical capacitor hybrid system has been presented in ref.[5], however the validity of the model on comparison with experimental data has not been done. The present work compares the simulations with experimental data obtained on Sony US 18650 cells with Maxwell PC 100F electrochemical capacitor hybrid system for pulse current discharges. The model has also been used to study some limiting conditions on the performance of the battery.
This report summarizes the research done on concrete reinforcing steel corrosion at the Center fo... more This report summarizes the research done on concrete reinforcing steel corrosion at the Center for Electrochemical Engineering, University of South Carolina for the last eight years. The long-term performance of two commercial corrosion inhibitors (Grace DCI and Masterbuilder's RH 222) has been studied in model solutions and also in concrete samples. Results from corrosion testing for 89 months show that both DCI and RH 222 inhibitor were effective in passivating carbon steel reinforcement in the absence of chloride ions. The estimated corrosion rates for DCI inhibitor were similar to those estimated when RH 222 was used to protect the structure. Both DCI and RH 222 inhibitors are not effective in passivating the surface in the presence of chloride ions in the electrolyte. However, the samples protected with inhibitor showed lower corrosion rates when compared with the samples with no inhibitor in the concrete mix. Apart from this, the performance of stainless steel and MMFX2 steel are estimated for their use in concrete as reinforcements. Stainless steel has very low corrosion rate in corrosive chloride environments even in the absence of inhibitors. The MMFX steel shows better performance than A706 and A615 carbon steel. Also, in corrosive chloride environments the presence of calcium nitrite inhibitor improves the performance of MMFX steel as compared to A706 and A615 carbon steel. At last, sensors were developed to study in-situ the corrosion in Withers Swash bridge. The sensors indicate that corrosion is different for different locations of the bridge. Some areas still need more time for passivation (central deck), while other areas are already corroding (side spans). Suggestions were given for the construction of economic long lasting structures.
This project focused on addressing the two main problems associated with state of art Molten Carb... more This project focused on addressing the two main problems associated with state of art Molten Carbonate Fuel Cells, namely loss of cathode active material and stainless steel current collector deterioration due to corrosion. We followed a dual approach where in the first case we developed novel materials to replace the cathode and current collector currently used in molten carbonate fuel
The behavior of galvanized carbon steel samples was studied in Ca(OH)2 solutions, simulating the ... more The behavior of galvanized carbon steel samples was studied in Ca(OH)2 solutions, simulating the alkaline environment in reinforced concrete. Under shorter periods, it was seen that a passive layer was formed on the surface of the zinc coating. The film, however, was not stable for large periods of time. This was revealed by the long duration tests where the passive layer was disrupted and the carbon substrate was protected sacrificially by zinc dissolution. The presence of chlorides accelerated the passive layer breakdown. The role of calcium nitrite in inhibiting the corrosion process of zinc was also studied. It was found that zinc was not protected by nitrite in the presence of chloride ions. The inhibitor, however, significantly reduced the corrosion rate of the underlying steel.
Cement stabilization of backfill has been used for some time in mechanically stabilized earth typ... more Cement stabilization of backfill has been used for some time in mechanically stabilized earth type retaining walls. However, there has been no data on the corrosion life of galvanized steel reinforcement in this environment, which is intermediate in pH between normal soil and pure concrete. Field observations had indicated a potential corrosion problem at a particular site in Deer Park, Texas. Cement addition to backfill in the usual quantities, for example 7% or more, raised the pH environment to values close to that of normal concrete. At these levels, corrosion rates of zinc coatings were not significantly accelerated; if anything, corrosion rates were less than for unstabilized fill. Very small amounts of cement addition, in the order of 1-4% producing pH values significantly less than 12, could cause limited acceleration of corrosion. It is, therefore, advisable to control minimum cement levels and to encourage efficient mixing. The use of crushed concrete as backfill did not accelerate corrosion. This material, therefore, appears to be acceptable for this application.
Due to the high cost of Pt catalyst, reducing the amount of Pt in electrodes is one of the primar... more Due to the high cost of Pt catalyst, reducing the amount of Pt in electrodes is one of the primary issues in polymer electrolyte membrane fuel cells. In this study, the hybrid cathode catalyst using the electrochemically active carbon composite catalyst and Pt catalyst is developed in order to reduce the amount of Pt and increase the overall catalytic performance. The carbon composite catalyst (CCC) is synthesized by pyrolysis of Fe-Co chelate compound followed by acid leaching. The current density of Pt/CCC is 1.5-6-fold higher than that of Pt/CB when employing ultra-low Pt loading (0.04 mg Pt cm −2). It is found that the Pt/CCC with the ultra-low Pt loading at tuned operating conditions exhibits a higher fuel cell performance than the Pt/CB and commercial Pt/C with four times higher Pt loading (0.16 mg Pt cm −2). The extensive activity of Pt/CCC is ascribed to the synergistic effect through (1) the combined activity of catalytic sites present in the CCC support and Pt, (2) the welldistributed nanoparticles and (3) the increased metallic Pt 0 concentration which indicated that the pyridinic-N played a role of oxide-cleanser.
The overall objective of this work was development proton exchange membrane (PEM) fuel cell catal... more The overall objective of this work was development proton exchange membrane (PEM) fuel cell catalysts for the oxygen reduction reaction (ORR) having ultra-low Pt loading with low cost, high performance and durability. The approach was based on development of a catalyst bridging the current platinum group metal (PGM) catalyst technology and the non-platinum cathode catalyst developed at USC. To balance the cost and the limited supply of platinum, the ultra-low platinum alloy project at (USC) developed highly stable and kinetically-activated carbon composite supports (A-CCS) as well as highly-active and stable hybrid cathode catalyst (HCC), Pt*/A-CCS (Pt* = Compressive Pt-lattice catalyst) that retain their activity after accelerated testing to simulate startup/shutdown and drive cycle potential cycling thus accomplishing the DOE 2017 targets. The HCC technology is based on a two-step patented process. 1-10 In order to develop a hybrid catalysts, in the first step, the following major constraints in the PEM fuel cells interfaces were addressed : (a) chemical and electrochemical stability of the support at high potentials, low pH and high temperature and (b) the support onset potential and kinetic activity for oxygen reduction reaction to be similar to that of a platinum catalyst. To accomplish these requirements, the A-CCS was synthesized with optimized: (i) BET surface area, porosity, pore-size and distribution and active sties for ORR (ii) hydrophilic/hydrophobic ratio, (iii) structural properties (amorphous/crystalline ratio). In the second step, compressive Pt-lattice catalyst (Pt*) was synthesized through a USC-developed annealing procedure that controls the particle size during annealing and forms monolayers of Pt* by diffusing Co atoms present in the support into Pt which is deposited on A-CCS support. In this step, Pt/Pt*-support interaction was optimized through inclusion of active surface functional groups, and through optimization of transition metal content in the alloy necessary for the formation of compressive Pt-lattice catalyst. The Pt*/A-CCS shows high mass activity (0.41 A/mg Pt), excellent support stability, and enhanced catalyst durability under accelerated stress test (AST) conditions. Initial mass activity, mass activity and ECSA loss after 30K cycles (0.6 -1.0 V- catalyst durability), potential loss after 30 K cycles (0.6-1.0-catalyst durability), potential loss after 5 K cycles (1.0-1.5V-support stability) and mass activity and ECSA loss after 5 k cycles (1.0-1.5V-support stability) will be compared in the presentation with 2020 DOE Technical targets for PEM catalyst and supports. References Ákos Kriston, Andreas Pfrang, Branko N. Popov, and L. Boon-Brett, “Development of a Full Layer Pore-Scale Model for the Simulation of Electro-Active Material Used in Power Sources,” Electrochem. Soc., 161 (2015) E3235-E3247. Kim, T. Xie, W.S. Jung, F. Gadala-Maria, P. Ganesan, B.N. Popov, Development of Catalytically Active and Highly Stable Catalyst Supports for Polymer Electrolyte Membrane Fuel Cells, J. Power Sources, 273, (2015) 761-774. Wonsuk Jung, Tianyuan Xie, Taekeun Kim, Prabhu Ganesan, Branko N. Popov, Highly Active and Durable Co-Doped Pt/CCC Cathode Catalyst for Polymer Electrolyte Membrane Fuel Cells, Acta, 167, (2015) 1-12. Takeun Kim , Branko N. Popov, Development of highly-active and stable Pt/C Catalyst for Polymer Electrolyte Membrane Fuel Cells Under Simulated Start up/Shut Down Cycling, International Journal of Hydrogen Energy, 41, (2016) 1328-1336. N. Popov, Jong-Won Lee, Sehkyu Park, Chapter Electrocatalyst for Low Temperature Fuel Cells,” John Willey and Sons, VCH, RE 9783527341320 (2016). Taekeun Kim, Tianyuan Xie, Won Suk Jung , Branko N. Popov, Development of Ultra-low Highly Active and Durable Hybrid Compressive Platinum Lattice Cathode Catalyst for Polymer Electrolyte Membrane Fuel Cells, International Journal of Hydrogen Energy, 42, (2017), 12507-12520. Won Suk Jung, Branko N. Popov, Improved Durability of Pt Catalyst Supported on N-doped Mesoporous Graphitized Carbon for Oxygen Reduction Reaction in Polymer Electrolyte Membrane Fuel Cells, Carbon, 122 (2017) 746-755. Won Suk Jung and Branko N. Popov, New Method to Synthesize Highly Active and Durable Chemically Ordered fct-PtCo Cathode Catalyst for PEMFC’s, ACS Appl. Mater. Interfaces, (2017), 9, 23879-23686. Won Suk Jung and Branko N. Popov, Hybrid cathode catalyst with Synergistic effect Between Carbon Composite Catalyst and Pt for Ultra –low Pt Loading in PEMFC’s, Catalysis Today, 295, (2017) 65-74.\ Won Suk Jung and Branko N. Popov, Effect of Pretreatment on Durability of fct-Structured Pt-Based Alloy Catalyst for Oxygen Reduction Reaction in Polymer Electrolyte Membrane Fuel Cells, ACS Sustainable Chem. and Eng, (09)(2017) DOI: 10.1021.
Cathode durability, cost, and performance are some of the key issues preventing the commercializa... more Cathode durability, cost, and performance are some of the key issues preventing the commercialization of polymer electrolyte membrane fuel cells (PEMFCs) for automotive applications. The support degradation during start-up/ shut-down and the catalyst degradation during driving potential cycling limit overall cathode catalyst lifetime. The ultra-low Pt cathode catalyst development project at the University of South Carolina (USC) has developed highly-stable activated carbon composite supports (ACCS) as well as highly-active and stable compressive Pt lattice cathode catalysts, Pt*/ACCS (Pt* = Compressive Pt lattice catalyst) that retain their activity after accelerated stress tests (AST) to simulate start-up/shut-down and driving potential cycling [1-7]. The novel USC technology is based on a two-step patented process. In the first step, the following major constraint was addressed: the support should be chemically and electrochemically stable at high potentials, low pH, and high temperature. To accomplish these requirements, ACCS was synthesized with optimization of: (i) BET surface area, porosity, pore-size and distribution, (ii) hydrophilic/ hydrophobic ratio, (iii) structural properties (amorphous/ crystalline ratio), and (iv) Pt-support interaction through inclusion of active surface functional groups. In the second step, compressive Pt lattice catalyst (Pt*) was synthesized through a USC-developed annealing procedure that controls the particle size during annealing and forms several monolayers of Pt* by diffusing Co atoms into Pt which is deposited on ACCS support. The Pt*/ACCS shows high rated power density (0.174 gPt kW−1), excellent support stability (8 mV loss at 1.5 A cm−2), and enhanced catalyst durability (24 mV loss at 0.8 A cm−2) under AST conditions. References [1] T. Kim, B. N. Popov, Int. J. Hydrogen Energ., 41 (2016) 1828-1836. [2] T. Kim, T. Xie, W. Jung, F. Gadala-Maria, P. Ganesan, B.N. Popov, J. Power Sources, 273 (2015) 761-774. [3] W. Jung, T. Xie, T. Kim, P. Ganesan, B.N. Popov, Electrochim. Acta, 167 (2015) 1-12. [4] T. Xie, W. Jung, T. Kim, P. Ganesan, B.N. Popov, J. Electrochem. Soc., 161 (2014) F1489-F1501. [5] Á. Kriston, T. Xie, B. N. Popov, Electrochim. Acta, 121 (2014) 116-127. [6] Á. Kriston, T. Xie, D. Gamliel, P. Ganesan, B. N. Popov, J. Power Sources, 243 (2013) 958-963. [7] Á. Kriston, T. Xie, P. Ganesan, B. N. Popov, J. Electrochem. Soc., 160 (2013) F406-F412. Figure 1
Low loading Pt and Pt-alloy hybrid cathode catalysts are developed for PEM fuel cell application.... more Low loading Pt and Pt-alloy hybrid cathode catalysts are developed for PEM fuel cell application. A novel low temperature pyrolysis procedure was developed for the synthesis of graphitic carbon composite supports and a polyol synthesis was employed for uniform Pt deposition on the carbon composite supports. Rotating ring disk electrode and fuel cell studies indicated the synergistic effect of hybrid cathode catalyst (HCC) which combines the catalytically active carbon composite support and Pt catalyst. The support durability test results indicated that both the HCC250-2nd generation catalyst and Pt/USC-AGC catalysts satisfy the 2017 DOE target of 30 mV loss after 400 h potential holding at 1.2 V under high current density operation in H2/air. The Pt/CCC140-3rd and Pt/USC-AGC catalysts show much lower mass activity loss (<40% loss) after 400 h potential holding experiment.
Journal of the Chemical Society, Faraday Transactions, 1996
Galvanostatic pulse and pulse reverse techniques have been used to study the plating of zinc-nick... more Galvanostatic pulse and pulse reverse techniques have been used to study the plating of zinc-nickel alloys in the presence of nonyl phenyl polyethylene oxide. The effects of average current density, rotation speed of disc electrode and the presence of nonyl phenyl polyethylene oxide in the electrolyte on deposition of zinc-nickel alloys were evaluated. Zinc-nickel plating bath solution chemistry was studied by determining the equilibrium concentrations at various pH levels. It was found that the alloy composition was determined by solution equilibria, mass transfer of the electroactive species within the diffusion layer and by the surface coverage of nonyl phenyl polyethylene oxide.
Cobalt coatings on metal hydrides give rise to an additional capacity due to the cobalt on the su... more Cobalt coatings on metal hydrides give rise to an additional capacity due to the cobalt on the surface of the alloy. In such a case, the galvanostatic discharge technique cannot be used to measure the diffusion coefficient of hydrogen in the alloy. We present here an analytical ...
Characterization of Sol-Gel-Derived Cobalt Oxide Xerogels as Electrochemical Capacitors.-Very fin... more Characterization of Sol-Gel-Derived Cobalt Oxide Xerogels as Electrochemical Capacitors.-Very fine cobalt oxide xerogel powders are prepared from CoCl 2 by use of a unique solution chemistry associated with the sol-gel process. Thermal treatment has significant effects on the surface area, pore volume, crystallinity, particle structure, and corresponding electrochemical properties. The highest average specific capacitance obtained is 291 F/g for a single electrode, and it corresponds to the CoOx xerogel electrode calcined at 150
Introduction: The superior power density feature of electrochemical double layer capacitors (desp... more Introduction: The superior power density feature of electrochemical double layer capacitors (despite its poor energy density) and the remarkably high energy density property of advanced batteries (despite its poor power density) presents an excellent case for the optimization of energy and power density by the combination of advanced battery systems and high surface area electrochemical double layer capacitors (commonly referred to as the hybrid systems). Several research attempts has been made on hybrid systems which exhibit extended run time and enhanced power capability of hybrid systems as against the battery alone systems. The optimization of these hybrid systems requires extensive experimental effort and so sophisticated models predicting the behavior of hybrid systems could be useful for determining optimization strategies. A model predicting the performance of a lithium-ion battery/electrochemical capacitor hybrid system has been presented in ref.[5], however the validity of the model on comparison with experimental data has not been done. The present work compares the simulations with experimental data obtained on Sony US 18650 cells with Maxwell PC 100F electrochemical capacitor hybrid system for pulse current discharges. The model has also been used to study some limiting conditions on the performance of the battery.
This report summarizes the research done on concrete reinforcing steel corrosion at the Center fo... more This report summarizes the research done on concrete reinforcing steel corrosion at the Center for Electrochemical Engineering, University of South Carolina for the last eight years. The long-term performance of two commercial corrosion inhibitors (Grace DCI and Masterbuilder's RH 222) has been studied in model solutions and also in concrete samples. Results from corrosion testing for 89 months show that both DCI and RH 222 inhibitor were effective in passivating carbon steel reinforcement in the absence of chloride ions. The estimated corrosion rates for DCI inhibitor were similar to those estimated when RH 222 was used to protect the structure. Both DCI and RH 222 inhibitors are not effective in passivating the surface in the presence of chloride ions in the electrolyte. However, the samples protected with inhibitor showed lower corrosion rates when compared with the samples with no inhibitor in the concrete mix. Apart from this, the performance of stainless steel and MMFX2 steel are estimated for their use in concrete as reinforcements. Stainless steel has very low corrosion rate in corrosive chloride environments even in the absence of inhibitors. The MMFX steel shows better performance than A706 and A615 carbon steel. Also, in corrosive chloride environments the presence of calcium nitrite inhibitor improves the performance of MMFX steel as compared to A706 and A615 carbon steel. At last, sensors were developed to study in-situ the corrosion in Withers Swash bridge. The sensors indicate that corrosion is different for different locations of the bridge. Some areas still need more time for passivation (central deck), while other areas are already corroding (side spans). Suggestions were given for the construction of economic long lasting structures.
This project focused on addressing the two main problems associated with state of art Molten Carb... more This project focused on addressing the two main problems associated with state of art Molten Carbonate Fuel Cells, namely loss of cathode active material and stainless steel current collector deterioration due to corrosion. We followed a dual approach where in the first case we developed novel materials to replace the cathode and current collector currently used in molten carbonate fuel
The behavior of galvanized carbon steel samples was studied in Ca(OH)2 solutions, simulating the ... more The behavior of galvanized carbon steel samples was studied in Ca(OH)2 solutions, simulating the alkaline environment in reinforced concrete. Under shorter periods, it was seen that a passive layer was formed on the surface of the zinc coating. The film, however, was not stable for large periods of time. This was revealed by the long duration tests where the passive layer was disrupted and the carbon substrate was protected sacrificially by zinc dissolution. The presence of chlorides accelerated the passive layer breakdown. The role of calcium nitrite in inhibiting the corrosion process of zinc was also studied. It was found that zinc was not protected by nitrite in the presence of chloride ions. The inhibitor, however, significantly reduced the corrosion rate of the underlying steel.
Cement stabilization of backfill has been used for some time in mechanically stabilized earth typ... more Cement stabilization of backfill has been used for some time in mechanically stabilized earth type retaining walls. However, there has been no data on the corrosion life of galvanized steel reinforcement in this environment, which is intermediate in pH between normal soil and pure concrete. Field observations had indicated a potential corrosion problem at a particular site in Deer Park, Texas. Cement addition to backfill in the usual quantities, for example 7% or more, raised the pH environment to values close to that of normal concrete. At these levels, corrosion rates of zinc coatings were not significantly accelerated; if anything, corrosion rates were less than for unstabilized fill. Very small amounts of cement addition, in the order of 1-4% producing pH values significantly less than 12, could cause limited acceleration of corrosion. It is, therefore, advisable to control minimum cement levels and to encourage efficient mixing. The use of crushed concrete as backfill did not accelerate corrosion. This material, therefore, appears to be acceptable for this application.
Due to the high cost of Pt catalyst, reducing the amount of Pt in electrodes is one of the primar... more Due to the high cost of Pt catalyst, reducing the amount of Pt in electrodes is one of the primary issues in polymer electrolyte membrane fuel cells. In this study, the hybrid cathode catalyst using the electrochemically active carbon composite catalyst and Pt catalyst is developed in order to reduce the amount of Pt and increase the overall catalytic performance. The carbon composite catalyst (CCC) is synthesized by pyrolysis of Fe-Co chelate compound followed by acid leaching. The current density of Pt/CCC is 1.5-6-fold higher than that of Pt/CB when employing ultra-low Pt loading (0.04 mg Pt cm −2). It is found that the Pt/CCC with the ultra-low Pt loading at tuned operating conditions exhibits a higher fuel cell performance than the Pt/CB and commercial Pt/C with four times higher Pt loading (0.16 mg Pt cm −2). The extensive activity of Pt/CCC is ascribed to the synergistic effect through (1) the combined activity of catalytic sites present in the CCC support and Pt, (2) the welldistributed nanoparticles and (3) the increased metallic Pt 0 concentration which indicated that the pyridinic-N played a role of oxide-cleanser.
The overall objective of this work was development proton exchange membrane (PEM) fuel cell catal... more The overall objective of this work was development proton exchange membrane (PEM) fuel cell catalysts for the oxygen reduction reaction (ORR) having ultra-low Pt loading with low cost, high performance and durability. The approach was based on development of a catalyst bridging the current platinum group metal (PGM) catalyst technology and the non-platinum cathode catalyst developed at USC. To balance the cost and the limited supply of platinum, the ultra-low platinum alloy project at (USC) developed highly stable and kinetically-activated carbon composite supports (A-CCS) as well as highly-active and stable hybrid cathode catalyst (HCC), Pt*/A-CCS (Pt* = Compressive Pt-lattice catalyst) that retain their activity after accelerated testing to simulate startup/shutdown and drive cycle potential cycling thus accomplishing the DOE 2017 targets. The HCC technology is based on a two-step patented process. 1-10 In order to develop a hybrid catalysts, in the first step, the following major constraints in the PEM fuel cells interfaces were addressed : (a) chemical and electrochemical stability of the support at high potentials, low pH and high temperature and (b) the support onset potential and kinetic activity for oxygen reduction reaction to be similar to that of a platinum catalyst. To accomplish these requirements, the A-CCS was synthesized with optimized: (i) BET surface area, porosity, pore-size and distribution and active sties for ORR (ii) hydrophilic/hydrophobic ratio, (iii) structural properties (amorphous/crystalline ratio). In the second step, compressive Pt-lattice catalyst (Pt*) was synthesized through a USC-developed annealing procedure that controls the particle size during annealing and forms monolayers of Pt* by diffusing Co atoms present in the support into Pt which is deposited on A-CCS support. In this step, Pt/Pt*-support interaction was optimized through inclusion of active surface functional groups, and through optimization of transition metal content in the alloy necessary for the formation of compressive Pt-lattice catalyst. The Pt*/A-CCS shows high mass activity (0.41 A/mg Pt), excellent support stability, and enhanced catalyst durability under accelerated stress test (AST) conditions. Initial mass activity, mass activity and ECSA loss after 30K cycles (0.6 -1.0 V- catalyst durability), potential loss after 30 K cycles (0.6-1.0-catalyst durability), potential loss after 5 K cycles (1.0-1.5V-support stability) and mass activity and ECSA loss after 5 k cycles (1.0-1.5V-support stability) will be compared in the presentation with 2020 DOE Technical targets for PEM catalyst and supports. References Ákos Kriston, Andreas Pfrang, Branko N. Popov, and L. Boon-Brett, “Development of a Full Layer Pore-Scale Model for the Simulation of Electro-Active Material Used in Power Sources,” Electrochem. Soc., 161 (2015) E3235-E3247. Kim, T. Xie, W.S. Jung, F. Gadala-Maria, P. Ganesan, B.N. Popov, Development of Catalytically Active and Highly Stable Catalyst Supports for Polymer Electrolyte Membrane Fuel Cells, J. Power Sources, 273, (2015) 761-774. Wonsuk Jung, Tianyuan Xie, Taekeun Kim, Prabhu Ganesan, Branko N. Popov, Highly Active and Durable Co-Doped Pt/CCC Cathode Catalyst for Polymer Electrolyte Membrane Fuel Cells, Acta, 167, (2015) 1-12. Takeun Kim , Branko N. Popov, Development of highly-active and stable Pt/C Catalyst for Polymer Electrolyte Membrane Fuel Cells Under Simulated Start up/Shut Down Cycling, International Journal of Hydrogen Energy, 41, (2016) 1328-1336. N. Popov, Jong-Won Lee, Sehkyu Park, Chapter Electrocatalyst for Low Temperature Fuel Cells,” John Willey and Sons, VCH, RE 9783527341320 (2016). Taekeun Kim, Tianyuan Xie, Won Suk Jung , Branko N. Popov, Development of Ultra-low Highly Active and Durable Hybrid Compressive Platinum Lattice Cathode Catalyst for Polymer Electrolyte Membrane Fuel Cells, International Journal of Hydrogen Energy, 42, (2017), 12507-12520. Won Suk Jung, Branko N. Popov, Improved Durability of Pt Catalyst Supported on N-doped Mesoporous Graphitized Carbon for Oxygen Reduction Reaction in Polymer Electrolyte Membrane Fuel Cells, Carbon, 122 (2017) 746-755. Won Suk Jung and Branko N. Popov, New Method to Synthesize Highly Active and Durable Chemically Ordered fct-PtCo Cathode Catalyst for PEMFC’s, ACS Appl. Mater. Interfaces, (2017), 9, 23879-23686. Won Suk Jung and Branko N. Popov, Hybrid cathode catalyst with Synergistic effect Between Carbon Composite Catalyst and Pt for Ultra –low Pt Loading in PEMFC’s, Catalysis Today, 295, (2017) 65-74.\ Won Suk Jung and Branko N. Popov, Effect of Pretreatment on Durability of fct-Structured Pt-Based Alloy Catalyst for Oxygen Reduction Reaction in Polymer Electrolyte Membrane Fuel Cells, ACS Sustainable Chem. and Eng, (09)(2017) DOI: 10.1021.
Cathode durability, cost, and performance are some of the key issues preventing the commercializa... more Cathode durability, cost, and performance are some of the key issues preventing the commercialization of polymer electrolyte membrane fuel cells (PEMFCs) for automotive applications. The support degradation during start-up/ shut-down and the catalyst degradation during driving potential cycling limit overall cathode catalyst lifetime. The ultra-low Pt cathode catalyst development project at the University of South Carolina (USC) has developed highly-stable activated carbon composite supports (ACCS) as well as highly-active and stable compressive Pt lattice cathode catalysts, Pt*/ACCS (Pt* = Compressive Pt lattice catalyst) that retain their activity after accelerated stress tests (AST) to simulate start-up/shut-down and driving potential cycling [1-7]. The novel USC technology is based on a two-step patented process. In the first step, the following major constraint was addressed: the support should be chemically and electrochemically stable at high potentials, low pH, and high temperature. To accomplish these requirements, ACCS was synthesized with optimization of: (i) BET surface area, porosity, pore-size and distribution, (ii) hydrophilic/ hydrophobic ratio, (iii) structural properties (amorphous/ crystalline ratio), and (iv) Pt-support interaction through inclusion of active surface functional groups. In the second step, compressive Pt lattice catalyst (Pt*) was synthesized through a USC-developed annealing procedure that controls the particle size during annealing and forms several monolayers of Pt* by diffusing Co atoms into Pt which is deposited on ACCS support. The Pt*/ACCS shows high rated power density (0.174 gPt kW−1), excellent support stability (8 mV loss at 1.5 A cm−2), and enhanced catalyst durability (24 mV loss at 0.8 A cm−2) under AST conditions. References [1] T. Kim, B. N. Popov, Int. J. Hydrogen Energ., 41 (2016) 1828-1836. [2] T. Kim, T. Xie, W. Jung, F. Gadala-Maria, P. Ganesan, B.N. Popov, J. Power Sources, 273 (2015) 761-774. [3] W. Jung, T. Xie, T. Kim, P. Ganesan, B.N. Popov, Electrochim. Acta, 167 (2015) 1-12. [4] T. Xie, W. Jung, T. Kim, P. Ganesan, B.N. Popov, J. Electrochem. Soc., 161 (2014) F1489-F1501. [5] Á. Kriston, T. Xie, B. N. Popov, Electrochim. Acta, 121 (2014) 116-127. [6] Á. Kriston, T. Xie, D. Gamliel, P. Ganesan, B. N. Popov, J. Power Sources, 243 (2013) 958-963. [7] Á. Kriston, T. Xie, P. Ganesan, B. N. Popov, J. Electrochem. Soc., 160 (2013) F406-F412. Figure 1
Low loading Pt and Pt-alloy hybrid cathode catalysts are developed for PEM fuel cell application.... more Low loading Pt and Pt-alloy hybrid cathode catalysts are developed for PEM fuel cell application. A novel low temperature pyrolysis procedure was developed for the synthesis of graphitic carbon composite supports and a polyol synthesis was employed for uniform Pt deposition on the carbon composite supports. Rotating ring disk electrode and fuel cell studies indicated the synergistic effect of hybrid cathode catalyst (HCC) which combines the catalytically active carbon composite support and Pt catalyst. The support durability test results indicated that both the HCC250-2nd generation catalyst and Pt/USC-AGC catalysts satisfy the 2017 DOE target of 30 mV loss after 400 h potential holding at 1.2 V under high current density operation in H2/air. The Pt/CCC140-3rd and Pt/USC-AGC catalysts show much lower mass activity loss (<40% loss) after 400 h potential holding experiment.
Uploads
Papers by Branko Popov