v. hydrogen - kocwcontents.kocw.net/kocw/document/2015/inha/baecksunghyeon/... · 2016-09-09 ·...
TRANSCRIPT
V. Hydrogen
Wasserstoff : The stuff of Water
Energy Carrier vs. Energy Source
Sustainable Energy
Higher Heating Value and Lower Heating Value
Hydrogen Production
Proven Industrial Technology
On-Site Hydrogen Processor 기술의 뿌리
Emerging Technology
기술 개발 노력과 시간을 요구
Hydrogen Production
Hydrogen Production from Fossil Fuel
In the short-term, hydrogen may
produced from fossil fuels
Natural gas
Coal
Gasoline
Advantages:
Established distribution networks
Economical conversion processes
Disadvantages:
Finite resources
Shift pollution problem, but don’t
eliminate it!
Natural Gas
48%
Oil
30%
Coal
18%
Electrolysis
4%
Steam Reforming
CnH2n+2 + nH2O => nCO + (4n+2)H2 Syn Gas
Water Gas Shift Reaction
CO + H2O => CO2 + H2
Hydrogen Production via reforming of hydrocarbon
Partial Oxidation (POX)
CnH2n+2 + n/2O2 => nCO + (n+1)H2
Preferential Oxidation (PROX)
CO + 1/2O2 => CO2
Hydrogen Production via Water Splitting
Hydrogen Evolution Reaction
2H+ + 2e- → H2 E0 = 0.0V (vs. NHE at 25oC)
-0.3 -0.2 -0.1 0.0 0.1-30
-25
-20
-15
-10
-5
0
Cu
rre
nt
de
ns
ity
/ m
Ac
m-2
E / V vs. RHEE / V vs. RHE
Overpotential
Oxygen Evolution Reaction
2H2O → O2 + 4H+ + 4e- E0 = 1.23 V (vs. NHE at 25oC)
0.8 1.0 1.2 1.4 1.6-10
0
10
20
30
40
50
60
70
Cu
rren
t d
en
sit
y / m
Acm
-2
E/V vs. RHE
Overpotential
Hydrogen Production from Nuclear Reactor
Advantages
Long-term energy resource
Reduced dependence on foreign energy supplies
No CO2 or air pollutant emissions
Disadvantages
Nuclear waste
Public acceptance
Material issues at high temperatures
Iodine-Sulfur Thermochemical Cycle
High Temperature Electrolysis
Hydrogen Production from Renewable Resources
For a true hydrogen economy (no net carbon emissions),
renewable resources must be used.
Possible renewable resources
Water Electrolysis
Biomass conversion
Biogeneration
Solar Energy
Wind Energy
Hydrogen Production from Biomass
Gasification, analogous to coal gasification, can turn crops or
crop residues to hydrogen
C6O6H14 (l)+ 6 H2O (l) 13 H2 (g)+ 6 CO2 (g)
Advantages:
CO2-neutral
Decreased dependence on foreign energy sources
Disadvantages
Very inefficient
Large amounts of land required (40% of current U.S.
cropland would be needed to power all cars)
Hydrogen Production from Biogeneration
Biogeneration uses microorganisms to generate hydrogen.
Bacteria can take organic wastes (proteins and carbohydrates)
and generate hydrogen.
For example, members of the Thermotogales family produce
hydrogen.
Advantages:
Environmentally benign
Moderate processing conditions
Disadvantages
Large-scale production has not been proven
Hydrogen Production from Solar Energy
Photovoltaic cells: solar energy is converted to
electricity which drives water electrolysis
Photoelectrochemical methods
Thermochemical methods
PV /Electrolysis Photoelectrochemical
(PEC) Cell
e-
H2
H2O
Pt
O2
H2O S.C.
hυ
Hydrogen Storage
Hydrogen Storage
Some of the most promising materials for
hydrogen storage
Metal hydrides (LaNi5H6, Mg2NH4, Na+(BH4)-, LiBH4)
Carbon nanotubes
Zeolites
Metal-organic framework materials
Al
H
Smalley 1996
Hydrogen Storage
Energy Density