Abstract: A device for improving combustion efficiency having an aluminum plate including a layer in one side thereof. The layer contains thorium oxide powder in a ratio of 1˜5 wt %. The device may be mounted in a section, such as a pipe, air cleaner, or fuel tank through which air, fuel or a mixture thereof passes. The air or fuel gets exposed to radiation of alpha-rays from thorium oxide power contained in the device resulting in air, fuel or a mixture thereof being activated. Since thorium oxide radiates primarily alpha-rays and almost no beta- or gamma-rays, the device promotes fuel combustion without any harm to human health. A method for producing the device is also disclosed.