# Presentation: 107991

## What Nanoporous Supports Do We Need for Solar Light-Driven Fuel Synthesis 

- What Nanoporous Supports Do We Need for Solar Light-Driven Fuel Synthesis

- Direct Solar to Fuel by Solid Photocatalysts
- Principle:

## Direct Solar to Fuel by Solid Photocatalysts

- Kudo, *J. Am. Chem. Soc.* **2003**, *125*, 3082.
- Q.Y. = 56%, > 400 hours
- ●  Direct solar to fuel works with UV light

- Where we are:
- UV light-driven Water Splitting: mixed metal oxide nanoparticles

## Direct Solar to Fuel by Solid Photocatalysts

- ●  Direct Solar to Fuel Works with UV Light

- Where we are:	UV light-driven CO2 reduction by H2O: Isolated Ti
- centers in nanoporous silicate

- Anpo, *Catal. Today* **1998**, *44*, 327
- Frei, *J. Phys. Chem. B* **2004**, *108*, 18269

##            Direct Solar to Fuel by Solid Photocatalysts	Where we are: Visible light-driven H2O → H2 + O2

- Water splitting with visible light observed, but very low efficiency.

- Single Component mixed metal oxide
- NiInTaO3

- Two-component mixed metal oxide
-  with shuttle (Z-scheme)

- Q.Y.= 0.3% at 420 nm
- Arakawa, *Science* **2001**, *414*, 625

- Q.Y.= 0.3% at 500 nm
- Kudo, *Chem. Commun*. **2001**, 2416

## Direct Solar to Fuel by Solid Photocatalysts

- Where we are:  Visible light-driven CO2 Splitting
- Binuclear photocatalytic sites on inert mesoporous oxide support

- Frei, *J. Am. Chem. Soc*. **2005**, *127*, 1610

## What we need

**Fact:**
- 	Numerous small bandgap semiconductor photocatalysts work efficiently under visible light (λ>600 nm, q.y.>50%), but require sacrificial reagents
- 	Lesson: no defects or ill-defined structures can be involved in energy transduction, charge migration, or catalytic transformation because they will invariably lead to loss of stored energy, charge, or chemical selectivity
**How can we avoid sacrificial reagents:**
- Active moieties (light harvesting, charge separation, catalytic sites) of **molecular** makeup
- Need **3-D high surface area ‘spectator’ support** for the molecular functionalities with precisely arranged (Angstrom) anchoring sites and structural elements for physical separation on the nanometer scale.
- Need to remove promptly the redox products from the reactive surface
- 	 exploit **gas-solid interface**

## What Active Molecular Components are Available:Some Examples

- 		 	Ru(bpy)32+ sensitizer/ Ni(cyclam) catalyst (CO2 to CO, H2O reduction)
- 		 Inorganic:
- 			IrOx Clusters  (H2O oxidation)
- 			MMCT units (CO2 splitting)

-      Organometallic:

## Organic/Metal Oxide Hybrid Functionalities on Mesoporous Supports

- Challenge: Incorporation of organic and polynuclear transition metal units at preselected sites and defined orientation inside silica wall

- top view

- side view

## Mixed Oxide Functionalities on Mesoporous Silica Supports

- Challenge: Ir oxide patches of defined composition and structure covalently linked to Co-O-Ti units inside mesoporous silica wall

## Solar to Fuel by Solid Photocatalysts:What needs to be done

**	**Develop methods that afford imprinting of molecular components and well-defined metal oxide clusters into walls of mesoporous nonreducible oxide supports at predetermined locations and with defined orientation
- 		New types of templates
- 		Methods for creating channel patterns with oxidizing/reducing sites
- 		Mesoporous membranes
- 		Defect-free active component/silica interface
- 	Design new catalytic components for coupled H2O oxidation/CO2 reduction