Aside from a hydrogen fuel cell, what other feasible sources of power are there for powering a small motor no bigger than the size of your palm.
Batteries, a DC source of electricity, are the common source of power for powering small motors. Fuel cells differ from batteries in that, unlike batteries, they cannot store energy on their own, but instead require electrolyzers and storage systems. Batteries as a source of power for a motor can come in many forms, from your everyday lead-acid battery that has an internally stored source of power that is depleted, to lithium-ion batteries, which can be recharged by plugging them into a power source like an electrical outlet in the wall. Motors in general can be powered by other DC sources such as motor vehicles or rectifiers, or by AC sources such as from the power grid (e.g., plugging it into the wall), inverters or generators.