Electrochem Flashcards
What are Batteries
Types
Electrochemical cells
Rechargeable
Non rechargeable
Example of rechargeable batteries
Lithium ion
What is the lithium battery electrode made from
And
The electrolyte
Electrode A- Lithium cobalt oxide (LiCoO2)
Electrode B- Graphite (C)
Electrolyte- lithium salt dissolved in organic solvent
What is a electrolyte
Conductive pathway for ions to move from one electrode to another
Half equations for lithium cell
Li+ + e- —> Li
Most negative E• so flip the equation
Li+ + CoO2 +e- —> Li+[CoO2]-
Most positive E•
Overall equation to use battery for lithium cell
Li + CoO2 —> Li+[CoO2]
EMF equation
E=R-O
How do rechargeable batteries work
Plug them to a current
Forces electrons to flow to the opposite direction
Reverse the overall equation to show a battery recharging
How is electricity generated in a fuel cell
Continuous external supply of chemicals
Example of fuel cell
Alkaline hydrogen-oxygen fuel cell
Hydrogen feed in fuel cell
Hydrogen is fed
It reacts with OH- ions in solution
2H2(g) + 4OH-(aq) —> 4H2O(l) + 4e-
Flow of electrons
Electrons made in the hydrogen feed travel through a platinum electrode
Platinum is a good conductor but inert
Component
Electron flow is used to power components
Oxygen feed
Oxygen gets fed
Reacts with water and the 4e- made from hydrogen feed to make OH- ions
O2(g) + 2H2O(l) + 4e- —> 4OH-(aq)
Negative electrode
Electrons flow to the negative electrode which is made from platinum
Electrolyte
Electrolyte is made of KOH solution
Carries the OH- ions from the negative to positive electrode
Positive electrode
Electrons flow from the positive electrode to the negative one
Also made from platinum
Water emission
Product of hydrogen feeding is released into the surroundings
Water
Movement of the OH- ions
OH- ions produced in the oxygen feeding are carried towards the positive electrode via the electrolyte
Ion exchange membranes
These surround the platinum electrodes and allow OH- ions yo pass but not the hydrogen or oxygen gas’s
Overall equation for fuel cell
2H2(g) + O2(g) —> 2H2O(g)
Pro of fuel cells
More efficient than internal combustion engines because of thermal energy loss
Don’t need to be recharged just re supplied
Only waste product is water
Con of fuel cells
Highly flammable hydrogen
Expensive to store and transport hydrogen
Energy is needed to make oxygen and hydrogen so fossils fuels may be used to make them
