The present invention provides a method for suppressing generation of hydrogen gas at the time when an ion concentration gradient is generated by a temperature responsive electrolyte. An electrolytic solution contains a temperature responsive electrolyte and an oxidation-reduction active species. The temperature responsive electrolyte is an electrolyte whose pKa varies according to the temperature. A power generating device performs power generation by using the electrolytic solution. The power generating device includes a positive electrode, a negative electrode, a heating mechanism, and a cooling mechanism. The positive electrode and the negative electrode are immersed in the electrolytic solution. The heating mechanism heats the electrolytic solution that is present in the vicinity of one of the positive electrode and the negative electrode. The cooling mechanism cools the electrolytic solution that is present in the vicinity of the other one of the positive electrode and the negative electrode.