Abstract: The invention concerns a device for purifying a gas effluent containing contaminants, comprising: a reactor including at least an inlet for the gas to be purified and at least an outlet for the purified gas ; at least an ultraviolet or visible radiation source; and at least a support element arranged inside the reactor and coated with a catalyst forming an exposed catalytic surface capable of oxidising at least partly the contaminants under the action of the ultraviolet or visible radiation. The reactor comprises at least two obstructing means, each of said obstructing means obstructing partly the flow of the gas effluent from said inlet up to said outlet and generating a turbulent gas zone on its downstream side, and a catalytic surface is arranged in each turbulent gas zone so that the turbulent gas flow is incident on said catalytic surface.