hydrogen fuel cells Flashcards
fuel cell type vs electrolyte
alkaline (afc). KOH. Potassium molten carbonate mcfx Molten LiCO3 proton exchange membrane pem solid oxide sofc. ceramic phosphoroc acid pafc. H3po4
what are advantages of fuel cells
no NOx or S0x
can use alternative fuels
cogeneration
what happens in low vs high temp?
at low temp
pefc, afc, pafc protons or hydroxyl ions are the major charge carriers in the electrolyte
at high temp
mcfc and sofc carbonate ions amd oxygen ions are the charge carriers
two developing fuel cell types?
pem —— proton exchange membrane
sofc —— solid oxide fuel cell
what is an anode?
conducts electrons freed from H.
disperses H gas over the surface of the catalyst
what are the components of proton exchange fuel cell
anode
cathode
electrolyte
catalyst
what is cathode?
conducts electron back from the external circuit
distributes O to the catalyst
what is a catalyst?
facilitates the H and O rxn
chemical rxn
anode side strips electrons 2h2=> 4h+ + 4e- cathode side combones electrons o2+ 4h+ +4e- => 2h2o net rxn 2h2+ o2 ==> 2h20
hydrogen fuel cell
electrochemical devices converts the chemical energy of a rxn directly into electrical energy.
uses hydrogen and oxygen
zero emissions
classes based on mobile ion (proton and ion exchange)
explain the chemical rxn for all fuel cells
2H2(g) +O2(g) -> 2H2O(liq)
an oxidation - reduction rxn
what are the functions of electrolyte?
transports dissolved reactants to the electrode
conducts ionic chg bet electrode and therefore completing the cell electric circuit?
provides physical barrier to prevent the fuel and oxidant gas streams from directly mixing.
what is a reformer?
turns HC or alcohol fuels onto hydrogen whixh is then fed into a fuel cell. can be external or internal.
what is a pem?
plastic
uses pure hydrogen for fuel
w a catalyst H atom splits imto a proton and electrom that take diff paths to cathode
advantage of pem
fast startup
light wt material
