Take a dc brushed motor when you apply a current to the motor it creates it's own generated force called back EMF. This restricts the current applied to the motor, when you slow the motor you reduce this back EMF which allows more current to flow, such as your starter motor on your car when it turns slowly it draws more current than when it spins quickly.
The idea of connecting a generator to a motor and creating power will fail because of losses in both the motor and the generator, the other force which comes into play is Faraday's law of induction and Lenz's law, this relates to the generator which effectively fights back against creating a current with an opposing magnetic field.
However, it is possible to make an electric motor carry out both functions of Rotational torque and generating a current.
Ah you say but what about Lenz's law which will prevent the motor from turning, good question and one which has taken me 5 years to overcome.
if you are interested in learning more and have experience in building electric motors please contact me. however if you have never heard of Lenz or Faraday my ideas will perhaps be beyond your current level of experience.