Ibrahim Pamuk - Academia.edu (original) (raw)

Papers by Ibrahim Pamuk

ACS Energy Letters, 2017

The fuel cell is a promising clean energy technology for efficient conversion of fuel to power wi... more The fuel cell is a promising clean energy technology for efficient conversion of fuel to power with no or low emissions (1). It utilizes electrochemical reactions and ion transport to generate electricity through redox-reactions (fuel oxidization, oxygen/air reduction). The main reaction product is water, sometimes also CO2 depending on the type of fuel used. Fuel cell applications range from small portable devices to medium-scale mobile and stationary uses (2). Solid oxide or ceramic fuel cells (SOFCs) are a promising fuel cell technology, but they are not yet fully commercial. The limited ionic conductivity of yttrium stabilized zirconia (YSZ) electrolytes used in SOFC requires a high operating temperature (800-1,000 o C), which imposes a major challenge on materials, durability, and costs (1). To improve their competitiveness, new pathways have been suggested such the intermediate temperature solid oxide fuel cells (IT-SOFC) (3), which operates below 600 o C. For example, IT-SOFC based on Ce0.85Sm0.15O2 and a eutectic mixture of Na2CO3, Li2CO3, K2CO3 has reached 1.1W/cm 2 at 550 o C (4). Another interesting development is the so-called single component fuel cell, which employs a mixture of ionic conductor and semiconductor materials, e.g. a perovskite La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) and Sm-Ca-co-doped ceria (SCDC) nanocomposite heterostructure (5), semiconductor-ionic Sr2Fe1.5Mo0.5O6-δ-Ce0.8Sm0.2O2-δ composite (6), or Sm-doped ceria (7) and NiZn-oxide nanocomposite material system. Instead of a traditional 3-layer fuel cell structure, the single-component approach integrates the cathode, electrolyte, and anode into one homogenous structure and one material called 3-in-1 (8). The SCDC-LSCF n-p heterojunction separates holes and electrons preventing short-circuiting or electrochemical leakage, whereas SCDC is also ion conducting (O 2-, H +) (see Fig.1) (6). Other materials of similar interest include e.g. YSZ-SrTiO3 (9,10) and SDC-SrTiO3 (7). Several research groups have demonstrated that such devices work satisfactorily. Similarly it has been reported that LiCoAlO2 (11) and SmNiO3 (12) oxides experience a transition from a semiconductor to a H + ionic conductor under fuel cell conditions. Performance results reported are around 500-600W/cm 2 at 500 o C, the best exceeding 1 W/cm 2 (6). The traditional solid oxide fuel cell technology closest to this design reaches 300-400W/cm 2 at 700 o C. The lower operational temperature, high power density, and only one material layer make the single-component fuel cells an interesting alternative for low-cost massproduction. Based on reported characteristics and promising single cell results, the singlecomponent fuel cell could possess potential for a technological breakthrough, but it is still hampered by some fundamental questions such as repeatability of experiments reported, lacking broader theoretical explanation of experiments albeit tentative efforts in this direction, inconsistences in experimental setups , differences in device configurations, and varying reporting practices of results, many of which could, however, be overcome through more systematic research and more standardized research procedures. The theoretical background of the operational principle is also still under discussion (13,14).

The Chemical Engineering Journal, 1978

The parameters of a two-phase model for fluidized beds are determined by the application of a mom... more The parameters of a two-phase model for fluidized beds are determined by the application of a moment method. The experimental results obtained for four different fluidized beds with different diameters indicate that the dependences on radial position in the bed of the number of eddy diffusion units, of the number of transfer units and of the fractional flow through the bubble phase are negligible. The variation of these parameters with bed height is found to be small, especially in columns with diameters of less than 4 cm. The volume fraction of the bubble phase is found to be correlated with the superficial gas velocity.

Effect of Nano Ion Conductor Infiltration on the Performance of Anode Supported Solid Oxide Fuel Cells

ECS Transactions, 2009

A high performance anode supported solid oxide fuel cell (SOFC) is developed by low-cost tape cas... more A high performance anode supported solid oxide fuel cell (SOFC) is developed by low-cost tape casting, co-sintering and nano-ion conductor infiltration techniques. The mixture of gadolinium and cerium nitrate solution is infiltrated into both anode and cathode layers and fired at a temperature that gadolinium nitrate and cerium nitrate undergoes a solid state reaction and forms nano ion conductor phase in both electrodes. The effect of molar concentrations and firing temperature of nano ion conductor phase on the cell performance are investigated. The measurements show that nano-sized ion conductor infiltration significantly improves the cell performance. The cell provides 1.718Wcm-2 maximum power density at an operation temperature of 750{degree sign}C. The high performance is attributed to increase in the oxide ion conductivity and three phase boundaries of both anode and cathode layers by nano ion-conductor infiltration.

ACS Energy Letters, 2017

The fuel cell is a promising clean energy technology for efficient conversion of fuel to power wi... more The fuel cell is a promising clean energy technology for efficient conversion of fuel to power with no or low emissions (1). It utilizes electrochemical reactions and ion transport to generate electricity through redox-reactions (fuel oxidization, oxygen/air reduction). The main reaction product is water, sometimes also CO2 depending on the type of fuel used. Fuel cell applications range from small portable devices to medium-scale mobile and stationary uses (2). Solid oxide or ceramic fuel cells (SOFCs) are a promising fuel cell technology, but they are not yet fully commercial. The limited ionic conductivity of yttrium stabilized zirconia (YSZ) electrolytes used in SOFC requires a high operating temperature (800-1,000 o C), which imposes a major challenge on materials, durability, and costs (1). To improve their competitiveness, new pathways have been suggested such the intermediate temperature solid oxide fuel cells (IT-SOFC) (3), which operates below 600 o C. For example, IT-SOFC based on Ce0.85Sm0.15O2 and a eutectic mixture of Na2CO3, Li2CO3, K2CO3 has reached 1.1W/cm 2 at 550 o C (4). Another interesting development is the so-called single component fuel cell, which employs a mixture of ionic conductor and semiconductor materials, e.g. a perovskite La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) and Sm-Ca-co-doped ceria (SCDC) nanocomposite heterostructure (5), semiconductor-ionic Sr2Fe1.5Mo0.5O6-δ-Ce0.8Sm0.2O2-δ composite (6), or Sm-doped ceria (7) and NiZn-oxide nanocomposite material system. Instead of a traditional 3-layer fuel cell structure, the single-component approach integrates the cathode, electrolyte, and anode into one homogenous structure and one material called 3-in-1 (8). The SCDC-LSCF n-p heterojunction separates holes and electrons preventing short-circuiting or electrochemical leakage, whereas SCDC is also ion conducting (O 2-, H +) (see Fig.1) (6). Other materials of similar interest include e.g. YSZ-SrTiO3 (9,10) and SDC-SrTiO3 (7). Several research groups have demonstrated that such devices work satisfactorily. Similarly it has been reported that LiCoAlO2 (11) and SmNiO3 (12) oxides experience a transition from a semiconductor to a H + ionic conductor under fuel cell conditions. Performance results reported are around 500-600W/cm 2 at 500 o C, the best exceeding 1 W/cm 2 (6). The traditional solid oxide fuel cell technology closest to this design reaches 300-400W/cm 2 at 700 o C. The lower operational temperature, high power density, and only one material layer make the single-component fuel cells an interesting alternative for low-cost massproduction. Based on reported characteristics and promising single cell results, the singlecomponent fuel cell could possess potential for a technological breakthrough, but it is still hampered by some fundamental questions such as repeatability of experiments reported, lacking broader theoretical explanation of experiments albeit tentative efforts in this direction, inconsistences in experimental setups , differences in device configurations, and varying reporting practices of results, many of which could, however, be overcome through more systematic research and more standardized research procedures. The theoretical background of the operational principle is also still under discussion (13,14).

The Chemical Engineering Journal, 1978

The parameters of a two-phase model for fluidized beds are determined by the application of a mom... more The parameters of a two-phase model for fluidized beds are determined by the application of a moment method. The experimental results obtained for four different fluidized beds with different diameters indicate that the dependences on radial position in the bed of the number of eddy diffusion units, of the number of transfer units and of the fractional flow through the bubble phase are negligible. The variation of these parameters with bed height is found to be small, especially in columns with diameters of less than 4 cm. The volume fraction of the bubble phase is found to be correlated with the superficial gas velocity.

Effect of Nano Ion Conductor Infiltration on the Performance of Anode Supported Solid Oxide Fuel Cells

ECS Transactions, 2009

A high performance anode supported solid oxide fuel cell (SOFC) is developed by low-cost tape cas... more A high performance anode supported solid oxide fuel cell (SOFC) is developed by low-cost tape casting, co-sintering and nano-ion conductor infiltration techniques. The mixture of gadolinium and cerium nitrate solution is infiltrated into both anode and cathode layers and fired at a temperature that gadolinium nitrate and cerium nitrate undergoes a solid state reaction and forms nano ion conductor phase in both electrodes. The effect of molar concentrations and firing temperature of nano ion conductor phase on the cell performance are investigated. The measurements show that nano-sized ion conductor infiltration significantly improves the cell performance. The cell provides 1.718Wcm-2 maximum power density at an operation temperature of 750{degree sign}C. The high performance is attributed to increase in the oxide ion conductivity and three phase boundaries of both anode and cathode layers by nano ion-conductor infiltration.