This is an old article I came across for a then new material that could directly convert radiation into electricity, rather than via the heat produced like in regular RTG batteries.
It seems that the majority of our energy is produced by heating water, so work like this always interest me.
Perhaps more common now as I haven’t done the research into it but it uses a material made from gold, carbon nanotubes and lithium hydride. The gold is bombarded with radiation, producing high-energy electrons which are picked up by the carbon nanotubes and deposited into lithium hydride where they then move through electrodes producing current.
I’ll leave this here for easy reference in case we ever want to come back to it.