The device includes a combustor comprising an inlet chamber or region intended to receive a flow of fuel and a combustion supporter at high pressure, an outlet chamber or region or combustion product exhaust at relatively lower pressure, and at least one separation element of nano-porous or micro-porous semi-conductor material which separates the inlet chamber or region from the outlet chamber or region. The separation element has a plurality of nano-pores or micro-pores passing therethrough which define communication passages between the inlet clad chamber or region and the outlet chamber or region. The surface of these pores is at least partly clad in a layer of an electrically conductive or semi-conductive material which, relative to the semi-conductor material of the separation element forms an essentially extended junction, in particular a p-n junction or a Schottky junction or a hetero junction. First and second electrodes are connected to the cladding of the pores passing therethrough, and respectively, to the semi-conductor material of the separation element. In operation the pores act as confined microcombustion chambers and the energy developed by the combustion is able to cause creation of stable electron-hole pairs at the said junction and the generation of a corresponding potential difference between the electrodes.