Device (20, 29, 36, 38, 40) for converting thermal energy into chemical energy and chemical energy into electrical energy, comprising at least - a fuel cell unit, which includes at least - an anode comprising a first gas-permeable current collector and an anode-side catalyst, - a cathode comprising a second gas-permeable current collector and a cathode-side catalyst, - an electrolyte situated between the anode and the cathode, wherein at least the anode, the cathode and the electrolyte are situated in a chamber, and - an oxygen inlet to the chamber for supplying oxygen or an oxygen mixture to the cathode-side catalyst, - a fluid reservoir, which includes at least - a pyrocatalytically active material with at least one polar axis, - a first thermal energy carrier having a high temperature T H, - a second thermal energy carrier having a low temperature T K, and - a gas diffusion channel, wherein the chamber of the fuel cell unit is connected to the fluid reservoir via the gas diffusion channel, wherein the fluid reservoir contains at least the pyrocatalytically active material, which is subjected to changes of temperature over time ΔT/Δt, wherein the change of temperature ΔT/Δt is realized by means of an alternating heat transfer at the pyrocatalytically active material via a first thermal energy carrier having a high temperature T H and a second thermal energy carrier having a low temperature T K for the conversion of thermal energy into chemical energy, wherein for the high temperature T H a settable maximum temperature T Hmax of the pyrocatalytically active material is lower than the Curie temperature T C of the pyrocatalytically active material, wherein at the pyrocatalytically active material a reduction or oxidation of a fluid in the fluid reservoir to at least hydrogen as a chemical energy carrier takes place, wherein at least the hydrogen in the gas diffusion channel flows from the fluid reservoir to the anode-side catalyst, at which an oxidation of the hydrogen takes place for the conversion of chemical energy into electrical energy, and wherein intermediate chemical storage is possible at least in the gas diffusion channel as part of an arrangement (42, 43, 44, 45, 46) for intermediate storage. - a fuel cell unit, which includes at least - an anode comprising a first gas-permeable current collector and an anode-side catalyst, - a cathode comprising a second gas-permeable current collector and a cathode-side catalyst, - an electrolyte situated between the anode and the cathode, wherein at least the anode, the cathode and the electrolyte are situated in a chamber, and - an oxygen inlet to the chamber for supplying oxygen or an oxygen mixture to the cathode-side catalyst, - an anode comprising a first gas-permeable current collector and an anode-side catalyst, - a cathode comprising a second gas-permeable current collector and a cathode-side catalyst, - an electrolyte situated between the anode and the cathode, - an oxygen inlet to the chamber for supplying oxygen or an oxygen mixture to the cathode-side catalyst, - a fluid reservoir, which includes at least - a pyrocatalytically active material with at least one polar axis, - a first thermal energy carrier having a high temperature T H, - a second thermal energy carrier having a low temperature T K, and - a pyrocatalytically active material with at least one polar axis, - a first thermal energy carrier having a high temperature T H, - a second thermal energy carrier having a low temperature T K, - a gas diffusion channel,