Khalid Fatih

Advancements in the Direct Hydrogen Redox Fuel Cell

An alternative type of fuel cell in which the air cathode is replaced by the ferric ion was investigated. This hybrid between a polymer electrolyte membrane fuel cell and a redox battery showed promising performance even though components such as the membrane were not optimized. Power densities greater than 0.17 W/cm 2 were achieved with no platinum on the cathode. In addition, the liquid-redox cathode can eliminate the need for humidification and cooling for the fuel cell and provides greater design flexibility. Different aspects of the redox cathode were characterized and showed opportunity for further performance improvement.

Advancing Direct Liquid Redox Fuel Cells: Mixed-Reactant and In Situ Regeneration Opportunities

Two approaches pertaining to the direct liquid redox fuel cell (DLRFC) have been investigated and demonstrated: mixed-reactant operation and in situ regeneration of the redox couple. The former involves supplying a mixed methanol Fe 2+ /Fe 3+ redox electrolyte to the selective carbon cathode of the DLRFC and supplying the fuel to the anode via methanol crossover. This approach has the potential to significantly improve the cost, compactness, and volumetric and gravimetric power densities of the cell. The latter in situ regeneration approach involves substituting the fuel supply with air to spontaneously reverse the direction of electron flow in a DLRFC, which eliminates the need for an auxiliary regeneration unit and reduces the overall cost and complexity of a DLRFC system. Both modes of DLRFC operation, discharge, and regeneration, produce power that is unique compared to conventional systems.

High Fuel Concentration Direct-Liquid Fuel Cell with a Redox Couple Cathode

An approach to direct liquid fuel cells (DLFCs) has been investigated where the air cathode is replaced with a redox couple cathode. This different configuration, a direct liquid redox fuel cell (DLRFC), reduces the effect of fuel crossover, eliminates cathode flooding, allows the use of a carbon-based three-dimensional electrode for the cathode, and increases cell design flexibility. Furthermore, the use of a carbon-based cathode significantly reduces the fuel cells total platinum group metal content. Contrary to conventional DLFCs, high fuel concentrations can be employed in this type of configuration without depolarizing the cathode because the carbon-based cathode is selective to the redox couple only. Cyclic voltammetry (CV), differential scanning calorimetry (DSC), conductivity measurements, and fuel cell tests were used to characterize the system. CV and DSC have confirmed the electrochemical stability of methanol and the redox couple (Fe 2+ /Fe 3+ ) up to 70°C and in the potential window of 0-1.2 V vs a standard hydrogen electrode. DLRFCs at 70°C employing the Fe 2+ /Fe 3+ redox couple at the cathode delivered peak power densities 5 and 3 times greater than DLFC equivalents (ambient pressure air) for acidic anolytes containing 16.7 M CH 3 OH and 18 M HCOOH, respectively.

Evaluation of the Fe(III)/Fe(II) Redox Fuel Cell Cathode Couple in a Bioelectrolytic Solution

The use of redox fuel cells, in which oxygen is replaced by other oxidants such as ferric ions, can have significant advantages. The redox fuel cell can achieve high efficiencies and has other fuel cell advantages. Bioregeneration is one method of creating a closed cathode system with efficient catholyte regeneration. In the work discussed here, a Fe3+/Fe2+ redox simulated bio-electrolyte catholyte is characterized over a range of electrolyte concentrations and fuel cell operating conditions using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS).

Durability of PEMFC Cathodes Exposed to Toluene-contaminated Air

The effects of toluene contamination on the performance of polymer electrolyte membrane fuel cells (PEMFCs) were studied. The severity of the contamination effect increased with increases in the current density, the toluene concentration and air stoichiometry, but decreased with an increase in the back pressure. The effect of toluene contamination on current dynamic operation was also studied by cycling the current density from 0.0 to 0.2, and then to 1.0 A cm -2 at the presence of toluene. The degradation of the fuel cell performance during the current dynamic operation was accelerated by the presence of toluene.