14.7 fuel cells Flashcards
what is a primary battery?
non-rechargeable battery (eg. zinc-carbon / zinc-maganese dioxide)
how is a secondary battery recharged?
plug in & current is supplied -> e- flows in opposite way
what is the overall reaction of an alkaline hydrogen fuel cell?
2 H2 + O2 -> 2 H2O`
what is the electrolyte in an alkaline hydrogen fuel cell?
KOH
what are the 2 equations that occur in an alkaline hydrogen fuel cell?
4e- + 4H2O -> 2 H2 + 4 OH- (-0.83 V)
4e- + O2 + 2 H2O -> 4 OH- (+0.4V)
what are the 2 equations in acidic conditions of a hydrogen fuel cell?
2e- + 2H+ -> H2
4e- + 4H+ + O2 -> 2 H2O
what are 4 limitations of hydrogen fuel cells?
- expensive
- safety & feasibility of storing & transporting hydrogen
- limited life-time
- using toxic chemicals in production
what other substances are used in fuel cells? give an specific example.
hydrogen-rich (ethanol)
what are 3 advantages of using ethanol for a fuel cell?
- made from carbon-neutral source & renewable
- raw materials for fermentation are abundant
- less explosive & easier to store
what is the overall equation for a fuel cell using ethanol?
C2H5OH + O2 -> 3H2O + 2CO2
what is the (acidic) reaction that occurs at the O2 electrode?
4e- + 4H+ + O2 -> 2 H2O
