Solid Oxide Fuel Cells PDF

## Solid Oxide Fuel Cells Solid oxide fuel cells (SOFCs) are a type of fuel cell that uses all solid-state materials. ### SOFC Components * **Electrolyte:** Commonly yttria stabilized zirconia (YSZ), a ceramic material. * **Anode:** Where hydrogen reacts with oxide ions. * **Cathode:** Where oxy...

## Solid Oxide Fuel Cells Solid oxide fuel cells (SOFCs) are a type of fuel cell that uses all solid-state materials. ### SOFC Components * **Electrolyte:** Commonly yttria stabilized zirconia (YSZ), a ceramic material. * **Anode:** Where hydrogen reacts with oxide ions. * **Cathode:** Where oxygen reacts with electrons. ### SOFC Operating Conditions * **Temperature:** ~1000°C * **Fuel:** Can run on a variety of fuels, including hydrogen, methane, propane, butane, gasoline, diesel fuel, jet fuel, and biofuels. ### SOFC Reactions **Anode:** 2H₂ + 2O²⁻ → 2H₂O + 4e⁻ **Cathode:** O₂ + 4e⁻ → 2O²⁻ **Cell Reaction:** 2H₂ + O₂ → 2H₂O ### SOFC Advantages 1. High efficiency (75-80%) compared to traditional thermal power plants. 2. No recharging needed, as long as fuel and oxidizer are supplied. 3. No thermal or noise polution. 4. Environmentally friendly byproducts. ### SOFC Disadvantages 1. Fuel must contain hydrogen atoms. 2. Prone to "carbon coking" which can slow down the internal fuel reforming process. 3. Slow start-up time due to high operating temperature. 4. High operating temperature requires the use of precious metal catalysts, increasing costs. 5. Lowering operating temperature decreases ionic conductivity of the electrolyte. ### SOFC Improvements * Replacing YSZ electrolyte with CGO (cerium gadolinium oxide) electrolyte allows for a lower operating temperature of 500-600°C. * The lower operating temperature allows the use of stainless steel instead of ceramic as the cell substrate, which reduces cost and start-up time. ## Modern Batteries ### Zinc-Air Batteries Zinc-air batteries are powered by the oxidation of zinc with oxygen from the air. * **Anode:** Zinc particles mixed with an electrolyte such as KOH. Oxygen reacts with zinc to form zincate ([Zn(OH)₄]²⁻). * **Cathode:** Oxygen from the air reacts with electrons and forms hydroxyl ions. **Anode Reaction:** Zn + 4OH⁻ → [Zn (OH)₄]²⁻ + 2e⁻ **Cathode Reaction:** 1/2O₂ + H₂O + 2e⁻ → 2OH⁻ **Overall Reaction:** 2Zn + O₂ → 2ZnO ### Lithium-ion Batteries Lithium-ion batteries feature an intercalated lithium compound (Li-GIC) as the cathode and an intercalated lithium compound such as lithium cobalt(III) oxide (LiCoO₂), lithium iron phosphate (LiFePO₄), or lithium manganese oxide (LiMn₂O₄) as the anode. The electrolyte contains lithium hexafluorophosphate (LiPF₆), lithium tetrafluoroborate (LiBF₄), lithium perchlorate (LiClO₄) or lithium triflate (LiCF₃SO₃) dissolved in an organic solvent such as dimethyl carbonate or diethyl carbonate. * **Anode Reaction:** LiC → nLi⁺ + ne⁻ + C * **Cathode Reaction:** Li₁₋ₙCoO₂ + nLi⁺ + ne⁻ → LiCoO₂ * **Overall Reaction:** LiC + Li₁₋ₙCoO₂ → C + LiCoO₂ ### Methanol-Oxygen Fuel Cell Methanol-oxygen fuel cells have several advantages. * **Fuel:** Methanol is readily available and cheap. * **Fuel Reactivity:** Contains easily oxidizable hydroxyl group. * **Fuel Solubility:** Highly soluble in aqueous medium like sulfuric acid. * **Product:** Produces carbon dioxide, which is non-toxic. **Anode Reaction:** CH₃OH(l) + H₂O(l) → CO₂(g) + 6H⁺(aq.) + 6e⁻ **Cathode Reaction:** 1/2O₂(g) + 6H⁺ + 6e⁻ → 3H₂O **Overall Reaction:** CH₃OH + 1/2O₂ → CO₂ + 2H₂O ### Fuel Cell Applications * **Methanol-Oxygen Fuel Cells:** Space crafts, military large scale power production. * **Other Fuel Cells:** Not mentioned in the document.