# Presentation: 927315

## Nanotechnology for the Hydrogen Economy

*Senior Scientist and Director*
*Materials Science Division*
*with *
*Millie Dresselhaus MIT*
*Michelle Buchanan ORNL*

***Nanotechnology for ******the Hydrogen Economy***

*OSTP Hot Topics in Science and Technology*
*Nanotechnology: Energizing our Future*
*August 10, 2005*

## Preview

**Hydrogen: a solution to world energy challenges**
- 	- supply, security, local/regional pollution, climate change
**Basic research challenges and nanoscience solutions**
- 	- production
- 	- storage
- 	- use in fuel cells
** **
**The two hydrogen economies**
- 	- incremental: where we are now
- 	- mature: where we need to be
- 	- nanotechnology bridges the gap

## The Hydrogen Economy

**gas or**
**hydride**
**storage**

**H****2****O**

***storage***

## Hydrogen Use Today: Combustion

*internal combustion engines*
- BMW: 184 hp, 133 mph
- 190 mile range
- liquid hydrogen/gasoline
- Ford, Mazda, Hydrogen Car Co

*gas turbines*
- electricity generation
- jet engines
- H2/natural gas mixtures

*space heat, stoves*

## Hydrogen Use Tomorrow: Fuel Cells

- eliminate combustion and heat
- from energy conversion
- up to 60% efficiency

*better membranes*
- higher temperature
- higher ion conductivity

- monolayer catalysts
- Pt/metal substrate

- metal substrate

- catalytic activity

- Pt/Ir

- Pt/Rh

- Pt/Pd

- Pt/Au

- Pt

- Pt/Ru

* *R. Adzic, M. Mavrikakis, et al.,* *
*Angew. Chem. Int. Ed.* 44. 2132 (2005)

*better catalysts*
- less Pt
- higher activity

## Hydrogen Storage Today:  Gas and Liquid

***Hydrogen Storage Today:  Gas and Liquid***

*gaseous storage*
- 5000 psi = 350 bar
- 10000 psi = 700 bar
- fiber reinforced
- composite containers

*liquid storage*
- standard in stationary applications
- portable cryogenics for auto
- 30-40% energy lost to liquifaction

- within technological reach

## Hydrogen Storage Tomorrow: Solid State

- 300 mile driving range  storage density higher than liquid H2
- short refill time, good acceleration  fast charge, release rates

*core-shell *
- nanoparticle medium
- high surface area

*core:* high density storage
- nanoscale  fast transit time

*shell *: dissociation
- H2  2 H

- ~ 10 nm

- sub-surface atom controls surface behavior
-           • low H2 surface binding energy
-           • high H2 surface dissociation rate

- M. Mavrikakis et al., *Nature Materials* **3**, 810 (2004)

- H2 gas

*grand challenge for hydrogen economy*

*near-surface alloys*

**Notes:**
• here is one reason that the hydrogen storage problem is so difficult
• the graph shows the volume energy density vertically and the mass storage density horizontally, including the mass and volume of the storage container.
• compressed gas, LH2, and various hydrogen storage materials are shown.  LH2 looks very promising here, but one must remember that approximately 40% of the energy of H2 is used to liquify it.  Thus it is not energetically attractive.
• the hydrogen storage materials cluster around compressed gas H2
• for comparison, gasoline (+ its storage tank) stores energy at enormously high volume and mass densities.  It is very hard to find an energy storage medium that competes with gasoline.  Even the highest energy density batteries pale by comparison to either hydrogen or gasoline.

## Hydrogen Production Today: Reform Fossil Fuels

- need 10 - 15 times today’s production for light trucks and cars in 2040

## Hydrogen Production Tomorrow: Splitting H2O

*abundant resource*
*no geopolitical constraints*
*environmentally benign*

*solar electrolysis*
- functional integration
- at the nanoscale
- molecular transfer of
- energy and charge
- 6-18% efficiency in laboratory

*bio-inspired nanoscale assemblies *
- inexpensive Mn catalyst
- room temperature
- “one molecule at a time”

*porphyrin nanotube hybrids*
- porphyrin: harvests light
- Pt, Au: catalyst & electrodes
- assembly splits water
- in sunlight

-  J A Shelnutt., et al.,
*J. Am. Chem. Soc. 126*, 635 (2004)

## The Two Hydrogen Economies