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