A reactor unit for photocatalytic treatment of fluids such as air, includes a catalyser device (4) comprising a catalytic material support having a generally tubular shape defining a fluid flow channel extending around and along a fluid flow path and a photocatalytic material coated on at least a portion of an internal surface of the support, and a radiation source (30) received in a central portion of the catalyser device. The catalytic material support comprises a wall portion and a plurality of tapered protrusions (8) extending from an internal surface of the wall portion to a tip proximate to the radiation source, the tapered protrusions being arranged around the radiation source and along the fluid flow channel.
