Elucidating the role of dopants in the photocatalysis of ZnO nanowires for enhanced water remediation: A comprehensive analysis using Al, Ga, Cl, Cu, Sb, Al-Ga, and Al-Cl

As a sustainable semiconductor absorbing UV light while exhibiting high photocatalytic activity, ZnO in the form of nanowires has emerged as a promising candidate. Here, its intentional doping with Al, Ga, Cu, Sb, Cl, Al-Ga, and Al-Cl is investigated to thoroughly assess its effects on photocatalysis. We show that the photocatalytic processes are governed by center dot OH hydroxyl radicals, as the main reactive species degrading methyl orange, and that free hVB+ act as the primary active charge carriers on the surfaces of ZnO nanowires, regardless of the nature and concentration of dopants. The main degradation pathway is found to proceed through the oxidation reaction of a phenyl ring bearing the dimethyl amino group. The photocatalytic activity is further revealed to be higher for Sb and Cu acceptors than for Al, Ga and Cl shallow donors. Beyond its ranking, the photocatalytic activity is optimal for a specific concentration of dopants, from ten to several tens of ppm, except for Ga doping. 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 intentional doping of ZnO nanowires for photocatalysis and open perspectives to address chemical and technological challenges.