[Physics] What creates the high voltage in Van de Graff generator

Question

I tried to in detail, explain what creates the high voltage in a Van de Graff generator. But I got problem doing that.

Van de Graaff generator:

First some background of a Van de Graaff generator, there is a comb that is "combing" a rolling belt to create and transfer charge away to create a voltage in a ball shaped metal encasing.

More info about the whole process can be found here:
https://en.wikipedia.org/wiki/Van_de_Graaff_generator

My contradiction

Though, I never understood what creates the super high voltage (1 million volt) of a Van de Graaff generator? And an argument that contradicts the high voltage creations of a Van de Graaff generator is that the energy required to remove an electron of an atom(ionization energy) is just a few eV(around 5eV – 30eV). Assuming the voltage of this system is the same as the voltage required to remove an electron. Then, a Van de Graaff generator can only generate the same voltage as the voltage needed to remove one electron from the atom, (i.e. a few volts)?

I'm a bit reluctant on accepting that the voltage is proprtional to the amount of charge of the Van de Graaff generator, because voltage is always relative (Energy/Charge). It's like saying a battery can generate few million volts because it can carry a lot of charge.

Answer 1

This is how it works:

So there exists a power supply that provides the positive charge and removes the electrons. The comb is for distributing the charges.( Depending on the materials used one could accumulate negative charges and remove the positive ones)

The Concentration of Charge

It is important to realize that the charge on the roller is much more concentrated than the charge on the belt. Because of this concentration of charge, the roller's electric field is much stronger than the belt's at the location of the roller and lower brush assembly. The strong negative charge from the roller now begins to do two things:

It repels the electrons near the tips of the lower brush assembly. Metals are good conductors because they are basically positive atoms surrounded by easily movable electrons. The brush assembly now has wire tips that are positively charged because the electrons have moved away from the tips, toward the connection at the motor housing.

It begins to strip nearby air molecules of their electrons. When an atom is stripped of its electrons, it is said to be plasma, the fourth state of matter. So we have free electrons and positively charged atoms of air existing between the roller and the brush. The electrons repel from the roller and attract to the electronless brush tips while the positive atoms attract to the negatively charged roller.

The positively charged atomic nuclei from the air molecules try to move toward the negatively charged roller, but the belt is in the way. So now the belt gets "coated" with the positive charge, which it then carries away from the roller.

One should not confuse high voltage with high power. The video shows that it is not dangerous to be charged by a Van de Graaff generator.