Fuel compositions

1. A fuel cell system, comprising:

a fuel cell comprising an anode, a cathode, and an electrolyte between the anode and the cathode; and

a fuel source in fluid communication with the anode, the fuel source comprising a composition comprising a polymer, a fuel, a concentration gradient of material capable of reacting with water to form hydrogen, wherein the composition has a hardness of at least about 2 grams peak force, as determined by penetration test using a texture analyzer.

2. The system of claim 1 , wherein the fuel comprises at least about 40% by weight methanol, and the polymer comprises a network of chemical bonds including metals.

3. The full cell system of claim 1 , wherein the polymer comprises an inorganic element.

4. The full cell system of claim 3 , wherein the inorganic element is a transition metal.

5. The full cell system of claim 4 , wherein the transition metal is selected from the group consisting of titanium and zirconium.

6. The full cell system of claim 3 , wherein the inorganic element is a main group metal.

7. The full cell system of claim 6 , wherein the main group metal is selected from the group consisting of silicon, aluminum, and boron.

8. The full cell system of claim 1 , wherein the polymer comprises metal-nonmetal-metal bond.

9. The full cell system of claim 1 , wherein the material comprises a hydride.

10. The full cell system of claim 1 , wherein the rigid composition further comprises a flame retardant.

11. The full cell system of claim 1 , wherein the polymer comprises an organic polymer.

12. The full cell system of claim 1 , wherein the rigid composition further comprises a water-sorbing material.

13. The full cell system of claim 1 , wherein the rigid composition comprises cross-linked silica.

14. The fuel cell of claim 1 , wherein the polymer comprises a metal-nonmetal-metal bond.