[Zeeshan Manzoor]

how can i find the concentration of KOH which can produce maximum concentration of hydrogen gas if potential difference of 12v is applied supplying current of 18 Ampere ?? if we are using 316L stainless steel electrodes
    give me just equation or reference to find this... i shall be very thankful.

[Arkcon]

Its hard to follow you.  You probably mean something other than what you've written.

how can i find the concentration of KOH which can produce

OK, for electrolysis, you'll get different results with widely varying concentrations.  I can follow that.  10 ppm KOH, versus 50% KOH will give a different result, for sure.

maximum concentration of hydrogen gas

So different concentrations of KOH give different mixtures of H₂ gas, some high or some low?  Mixtures of what and hydrogen?  I can't follow.  You probably mean yield, as in amount.

if potential difference of 12v is applied supplying current of 18 Ampere ??

Yes.  There is likely a formula that relates yield to volts and amps.  I don't know it off hand, but someone here may be able to help.

if we are using 316L stainless steel electrodes  give me just equation or reference to find this... i shall be very thankful.

Sure.  But ... you seem to miss some of the basics.  And I feel this will be an annoying thread if we don't get the basics clear.  Do you know the chemical reaction for hydrogen production by electrolysis?  You really should start there.

[Enthalpy]

If you mean the amount of hydrogen:
It depends on the current multiplied by the time. Provided that the rest works properly, the KOH, voltage etc. influence the amount through the current that can flow.

More KOH helps the current through. There must be some limit at very high concentration. The solution gets more corrosive too.

A higher voltage helps the current pass BUT has very important drawbacks. Everything above the minimum (something like 2V) is wasted into heat, and unwanted reactions appear at higher voltages. 12V is far too much.

The good method is to use electrodes of big surface put close to an other. This increases the current without a big voltage.

If your power source is fixed 12V, put several electrolysis cells in series. Each one will produce hydrogen from the current that flows through, hence you get 3* or 4* more gas with 3 or 4 cells, and the cells share the voltage as 4V*3 or 3V*4, avoiding bad reactions.