Using chemistry to generate electricity Batteries Using chemistry to generate electricity

Dry Cell Batteries Common batteries (AA, AAA, 6V, 9V, etc.) Utilize electrolyte paste to minimize moisture content.

Dry Cell Batteries

Dry Cell Batteries Electron flow Zn (anode) is oxidized to lose 2 e- The NH4Cl paste gains to 2 e- to make NH3 and H2. MnO2 removes H2 and forms Mn2O3 and H2O.

Dry Cell Batteries More common alkaline batteries Use KOH as electrolyte paste to produce reaction under basic conditions. Have longer working life and longer shelf life Why? Zn anode corrodes less under basic conditions than acidic conditions.

Lead-Acid Storage Batteries Batteries used in automobiles

Lead Acid Batteries Consist of 6 cells in series (each produces 2V for a total of 12 V) Contains PbO2 cathode and Pb anode in sufuric acid solution. Pb(s) + PbO2(s) + HSO4-(aq) + 2H+(aq)  2PbSO4(s) + 2H2O(l) PbSO4 builds up on electrodes if run for too long without being charged (function of the alternator…) If too much builds up, battery goes dead.

Fuel Cells Reactants must be constantly replenished. Most common is Hydrogen-Oxygen fuel cell. H flows past anode (Pt catalyst) and undergoes oxidation O flows past cathode (similar catalyst) and undergoes reduction. Only product is water. Used in space shuttle program to provide drinking water for astronauts.

Other fuel cells Breathalyzers Measures ethanol content in bloodstream using redox reaction. Ethanol is oxidized to acetic acid Magnitude of electric current is directly proportional to alcohol content in bloodstream if calibrated correctly.

Rechargeable Batteries

Electrolytic Cells Electric current drives a nonspontaneous reaction through electrolysis. Eocell = negative since reaction is thermodynamically unfavored. Electrical force must be greater than cell potential.

Electrolytic vs. Galvanic Battery

Other uses Artifact restoration Electroplating Innovations in fuel cells For example: water + electricity  splits into H2(g) at the Cathode and O2(g) at the anode. If you could find a way to spontaneously use this method in conjunction with a fuel cell… that is the ultimate goal and will change the world.