The invention refers to a fuel cell device comprising an electrolyte device, which comprises an alkaline electrolyte means and an acid electrolyte means, wherein the fuel cell device is formed such that at least part of at last one reaction product produced at the electrolyte means can be supplied to the other electrolyte means. Moreover, the invention comprises a method of operating a fuel cell device, which includes the following steps: providing an alkaline electrolyte means and an acid electrolyte means, supplying at least one fuel and at least one oxidant, discharging reaction products, wherein at least part of at least one reaction product produced at an electrolyte means is supplied to the other electrolyte means.