The supplementary figure illustrates the operation principle of a Solid-Cathode Fuel Cell (SCFC) under a propane-air mixture. In this single-chamber fuel cell, both the anode and cathode are exposed to the same air-propane mixture. The anode is active for propane partial oxidation and electro-oxidation of the resulting hydrogen (H₂) and carbon monoxide (CO), while the cathode is active for oxygen electro-reduction. These reactions generate an oxygen partial pressure gradient across the fuel cell, creating a voltage that can be used for power generation. The exothermic nature of the partial oxidation reaction can cause the fuel cell temperature to be significantly higher than that of the furnace used to maintain it. Ideal electrodes are designed to be active only for the desired reactions and inert to others, ensuring efficient and selective operation.The supplementary figure illustrates the operation principle of a Solid-Cathode Fuel Cell (SCFC) under a propane-air mixture. In this single-chamber fuel cell, both the anode and cathode are exposed to the same air-propane mixture. The anode is active for propane partial oxidation and electro-oxidation of the resulting hydrogen (H₂) and carbon monoxide (CO), while the cathode is active for oxygen electro-reduction. These reactions generate an oxygen partial pressure gradient across the fuel cell, creating a voltage that can be used for power generation. The exothermic nature of the partial oxidation reaction can cause the fuel cell temperature to be significantly higher than that of the furnace used to maintain it. Ideal electrodes are designed to be active only for the desired reactions and inert to others, ensuring efficient and selective operation.