Creating higher voltage from DC motor?
Absolutely! That is the basis for motor-generators, which, before power semiconductors, were one of the few devices able to change DC voltage with comparatively little loss.

Of course, stepping up voltage comes with a concomitant reduction of current, so you don't gain any power. E.G. 12 volts at 30 amps is equivalent to 120 volts at 3 amps, 360 watts. 

But you don't actually break even. If the motor has an efficiency of 95%, and the generator has the same efficiency (those are high figures), the combined efficiency is 90.25%, so with 360 watts in, you'd get only ~325 watts out. TANSTAAFL, as Heinlein summarized the first law of thermodynamics.

Or, maybe not! It's possible to get instantaneous power far exceeding the input power due to a flywheel effect. The motor and generator armatures store kinetic energy as they spin up, so that even with the motor disconnected, energy can be withdrawn until rotation ceases. Sadly, though, you still get less out than what you put in while spinning things up. Heinlein got it right.