You need voltage multiplier. Refer the following circuit. I haven’t tried it on 2 volts, but I hope it will work if you use germanium diodes.
I assume that you have 2 volts in the form of varying sine wave. If it is so you will get 8 volts at the output. Now use a 7805 regulator to make it stable at 5 volt
Give it a try and please update the result.