Optimization of aluminum doped ZnO nanowires for photoelectrochemical water splitting

•Aluminum doping influences the morphology of ZnO nanowires.•2-fold increase of the specific area current density (Turn Over) upon ZnO doping with Al ions.•3-4fold increase in charge carrier density caused by Al ions.•2-3fold increase of the electrocatalytically active sites caused by Al ions.•0.5 at.% Al-doped ZnO NWs exhibit the best photoelectrocatalytic performance. Undoped and aluminum-doped ZnO nanowire (NW) arrays with high aspect ratio and doping concentration up to 2.0 at.% in Al, were prepared by chemical bath deposition (CBD) technique onto FTO/glass substrates. The morphological, structural, and optical properties of the as-grown NWs were investigated by using electron microscopy, diffraction, and spectroscopic techniques. The prepared samples were used as photoanodes in a photoelectrochemical cell and their effectiveness for water splitting was evaluated. The optimum doping concentration was found to be 0.5 at.%. The increase of the photocurrent density normalized by the specific surface reaches up to 110% (in relation to the neat ZnO photoanode at 1.23 V) for this concentration The improved photocurrent density cannot be accounted for solely by the improvement of the conductivity by Al doping and the change in morphology; hence, the promoting effect of Al ions and the photoactivation of a larger fraction of sites has been evoked. [Display omitted]