Yes indeed, it is the reverse of electrolysis ! A diagram of the experiment of electric power generation by a fuel cell is explained on the home page. First of all, let's attempt the experiment of the electrolysis of water. Add the electrolyte to water, and when the battery is connected immersing a carbon rod (Core of pencils) and a copper plate as an electrode, hydrogen is generated on the cathode and oxygen is generated on the anode. Have the means to store hydrogen and oxygen in test tubes so that they do not escape. When the hydrogen and oxygen are completely filled up and in contact with an electrode, remove the battery and connect a fairy lamp in its place. Then, the fairy lamp lights up at this time, and you can see that electricity flows accordingly. In the negative pole, the stored hydrogen and ion hydroxide react with each other, and then electrons are generated and flow through the electric wire that makes the fairy lamp light up. In the positive pole, water and oxygen react, giving electrons that produce ion hydroxide. Thus, the ion hydroxide (OH-) generated on an anode moves in the electrolyte, while ion hydroxide reacts with hydrogen in a cathode that produces electrons. These electrons flow to an anode through the electric wire and the fairy lamp, which enables the fairy lamp to be lit up. Since these chemical formulas become the reverse of the arrows of the chemical equations for the electrolysis of water as mentioned above, it is represented as "the reverse of the electrolysis of water in a fuel cell mechanism". Described here is a principle of electric power generation of a fuel cell, called the alkali form (Ion hydroxide is alkaline). In recent years, in a fuel cell in polymer electrolyte form which has been a focus of attention for residential and motor vehicle use, the hydrogen ion (H+) moves between electrodes in place of ion hydroxide (OH-). The following is the chemical equation.       A run-through of the electrolysis of water   A variety of fuel cells