One of the most common preparation methods is electrolysis. In a specially designed electrolytic cell, water decomposes under the action of an electric current. At the cathode, hydrogen ions gain electrons and are converted into hydrogen gas. This hydrogen gas then dissolves in the surrounding water, thus forming hydrogen - rich water. This method is relatively easy to operate. Moreover, by adjusting the current intensity and electrolysis time, the concentration of hydrogen in the hydrogen - rich water can be effectively controlled. For instance, many household hydrogen - rich water machines mainly adopt the electrolysis method, enabling consumers to produce hydrogen - rich water at any time.