UV photocatalysis of ZnO nanowires: the issues of polarity and doping

As a sustainable wide bandgap compound semiconductor absorbing UV light while exhibiting high photocatalytic activity, ZnO in the form of nanowires has been considered as a promising candidate. Here, its polarity and its intentional doping with Al, Ga, Cu, Sb, Cl, Al-Ga, and Al-Cl are investigated to thoroughly assess their effects on the photocatalytic activity and processes. The photocatalytic processes in ZnO nanowires are found to be governed by the action of •OH hydroxyl radicals, as the main reactive species degrading methyl orange, and hence by free hVB+ acting as the primary active charge carriers on the surfaces of ZnO nanowires, regardless of the nature and concentration of dopants. The photocatalytic activity is further shown to be higher for acceptors than for shallow donors, and to preferentially act on the polar +c-plane top of ZnO nanowires. Eventually, a photo-corrosion phenomenon is concomitant with the photocatalytic processes, raising concerns about the chemical stability of ZnO nanowires. These findings revisit the effects of polarity and intentional doping of ZnO nanowires for photocatalysis and open perspectives to address chemical and technological challenges.