Sodium Silicide (NaSi) Synthesis, Reversability
The reaction of $\ce{NaSi}$ with water is both highly enthalpically and entropically favored—the reaction produces 5 molecules of $\ce{H2}$ gas for every 2 $\ce{NaSi}$ molecules that react, and the enthalpy of reaction is –175 $\mathrm{kJ\ mol^{-1}}$. The reverse reaction would require ludicrous amounts of energy and is likely not even kinetically feasible. 

It would be especially pointless to attempt the reverse reaction when $\ce{NaSi}$ is generated easily enough from $\ce{Na}$ and silica gel. Liquid sodium-potassium alloy absorbed onto silica gel results in a fine black powder that spontaneously ignites in humid air. Heating $\ce{Na}$ and silica gel to 165ºC with continual agitation produces a shelf stable, yet still highly reactive $\ce{NaSi}$. When slowly heated to 400ºC, air stable $\ce{NaSi}$ may be produced, though with less reducing power than those produced via the other two methods. It will, however, still react with water to produce $\ce{H2}$ and $\ce{ Na2Si2O5}$.$^{[1]}$




$^{[1]}$ Alkali Metals Plus Silica Gel:  Powerful Reducing Agents and Convenient Hydrogen Sources