Fuel Cells and Rechargeable Batteries C5

C.5.1 Describe how a hydrogen oxygen fuel cell works. Alkaline fuel cells usually use a mobilized or immobilized aqueous solution of potassium hydroxide as an electrolyte but sodium hydroxide is also acceptable.Alkaline fuel cells usually use a mobilized or immobilized aqueous solution of potassium hydroxide as an electrolyte but sodium hydroxide is also acceptable. The electrochemical reactions inside the fuel cell are:The electrochemical reactions inside the fuel cell are: 2H 4 +4OHֿ→ 4H 2 O+4eֿ anode reaction O 2 +4eֿ+2H 2 O→4OHֿ cathode reaction 2H 2 +O 2 →2H 2 O overall reaction Acid Fuel CellsAcid Fuel Cells Porous carbon anode with catalyst in contact with H 2 (g) H 2 (g)→2H + (aq)+2eֿ Cathode: porous carbon cathode with catalyst in contact with O 2 O 2 +4H + +4eֿ→2H 2 O

C.5.2 Describe the workings of rechargeable batteries A lead-acid battery is a electrical storage device that uses a reversible chemical reaction to store energy. Cathode: PbO 2 (s) + 2e- + 4 H+ (aq ) + SO 4 2- (aq ) --> PbSO 4 (s) + 2 H 2 O (l ) Anode: Pb (s) + SO 4 2- (aq ) --> PbSO 4 (s) + 2e- The nickel-cadmium battery (commonly abbreviated NiCd or nicad) is a type of rechargeable battery using nickel oxide hydroxide and metallic cadmium as electrodes. This battery uses nickel oxide in its positive electrode (cathode), a cadmium compound in its negative electrode (anode), and potassium hydroxide solution as its electrolyte. The Nickel Cadmium Battery is rechargeable, so it can cycle repeatedly. A nickel cadmium battery converts chemical energy to electrical energy upon discharge and converts electrical energy back to chemical energy upon recharge.

Continued. Cd + 2H 2 O + 2NiOOH —> 2Ni(OH) 2 + Cd(OH) 2 A Lithium-ion battery (sometimes Li-ion battery) is a type of rechargeable battery in which lithium ions move from the anode to cathode during discharge, and from the cathode to the anode when charged.

Similarities and differences between a fuel cell and a rechargeable battery In principle, a fuel cell operates like a battery. Unlike a battery however, a fuel cell does not run down or require recharging. It will produce electricity and heat as long as fuel and an oxidizer are supplied. It will produce electricity and heat as long as fuel and an oxidizer are supplied. Both batteries and fuel cells are electrochemical devices. both have a positively charged anode, a negatively charged cathode and an ion-conducting material called an electrolyte. Fuel cells are classified by their electrolyte material A rechargeable battery (also known as a storage battery) is a group of one or more secondary cells Rechargeable batteries use electrochemical reactions that are electrically reversible