Controlled Sodium Reaction?

Is it possible to control a sodium or lithium reaction so it doesn't explode, it just quickly produces H2 and O2 which could be used in vehicle, so it needs to be safe, and fool proof.

There are lots of things that are possible.

Explosions by themselves are not a problem, provided these explosions are small enough to be contained, after all this is what provides the power that drives most cars down the road.

It is conceivable that if you had a sturdy water filled reaction chamber, and you dripped in liquid sodium metal (its melting point is only 98C), drop by drop, that this could work as a on-demand hydrogen source.

But I wouldn't exactly call this fool-proof.  Keeping air out of the sodium-tank and sodium supply lines is going to be a problem.  Also there is the possibility of  a big explosion if somehow a large amount of water were to enter the sodium tank all at once, e.g. if you crashed this car into a lake.

But I think you need to take a step back and consider the fact that there are other ways to make hydrogen.  In fact there are whole bunch of other metals, besides sodium or lithium, which are capable of reducing water to hydrogen. That is:

 M +  n H2O ---->  M(OH)n +(n/2) H2

where M is some metal, and n is its favorite oxidation state.

The only trouble is, not every metal in the periodic table is as reactive with water as are Na or Li.  You can't just  throw a chunk of say iron, or aluminum, into a water at room temperature, and expect to get a reaction.  For example, iron (Fe), can reduce water to hydrogen, but only if the water is in the form of superheated steam.  (Well actually there is this guy in Texas who says he can reduce water using iron at room temperature, and I'll link to him later.)  Also aluminum (Al) is reactive enough to reduce water to hydrogen, but there's this pesky passivation layer that is always forming on the surface of any piece of Al metal.  To make hydrogen from Al you need to figure out a way to break through the passivation layer.

Actually there are a number of instructables on the subject of making H2 from Al metal.
https://www.instructables.com/pages/search/search.jsp?q=hydrogen+aluminum
You've probably seen some of them already.

Back to the overview.  As another consideration for your plans to make H2 from some kind of metal and water, is the issue of the cost/availability of your metal.  That's why you should probably go with a metal like Al or Fe, just because those are cheap, and really easy to get.  Zn is a good candidate too.

Another consideration is how toxic the metal is.

Based on these considerations, if you really want to use sodium or lithium, then pick sodium, because lithium is kind of rare and expensive.  I'll admit that it is easier to find Li metal on the street, in the form of lithium batteries, but that's just sort of a peculiarity of the marketplace.  On a large scale, sodium should be easier to get.  Also I think sodium and its salts are less toxic.

But it would really be better if you could run your hydrogen generator off of something cheaper and easier to handle, like aluminum or iron. 

Of course you and I are not the first to have thought about this problem.  

If you search, you can find various patents for devices intended to make hydrogen from these metals.  I'll link to just a few of the most intriguing ones I've seen, but if you want to see the big list, of almost everything under the sun, you can probably find it here:
http://www.rexresearch.com/1index.htm
Or here:
http://www.peswiki.com/index.php/Main_Page

Anyway the first is a hydrogen generator that runs on Al wire, the same kind you buy on spools for a wire-feed welder.
http://www.freepatentsonline.com/4702894.html

The next is Dr. Griffin.  He claims to have something that can make hydrogen from metallic iron (powder, if remember correctly) at room temperature, or close to room temperature.

http://www.rexresearch.com/griffin/griffin.htm
http://www.google.com/search?q=linnard+griffin+hydrogen&hl=en
 
Final note:  it does not have to be one metal or another.  If you can make an alloy of more than one metal, for example Na and Al, then you might get something, stable in air at room temperature, that you can drop into water to make hydrogen.  I seem to recall someone doing exactly this.  I mean it was some alloy, but I don't remember exactly what metals it was made of, (maybe Na, K, and Al?) and unfortunately I can't seem to find the link.





Oh, I forgot to mention wood. Wood is not metal, but wood can be used to make hydrogen, sort of. The usual product is a combination of carbon monoxide and hydrogen, called wood gas, town gas, syngas, producer gas, and probably other names.

https://www.instructables.com/id/Convert-your-Honda-Accord-to-run-on-trash/