Ex-situ flame co-doping of tin and tungsten ions in TiO2 nanorod arrays for synergistic promotion of solar water splitting

Ex-situ doping has an obvious advantage in tailoring the intrinsic properties of semiconductor due to the crucial dopant depth-control. However, the developed ex-situ doping technologies encounter dilemmas of high cost and low yield. Herein, we report an efficient, facile and depth-controllable ex-situ flame doping and the TiO(2 )nanorod arrays, dopants of Sn and W ions are prototypical system for photoelectrochemical water splitting, in which the dopants are diffused quickly into the outer surface region of the TiO2 in less than 30 s. The characterizations and theoretical calculations reveal that the enhanced electron localization on coordinatively unsaturated W atoms is induced by adjacent Sn atoms, which not only facilitate to absorb H2O molecules but also diminish activation energy barrier through stabilizing the *OH intermediates during oxygen evolution reaction. The desirable ex-situ flame doping strategy exhibits great versatility in the configuration of efficient photoelectrochemical systems over prevalent metal-oxide semiconductors. (C) 2020 Published by Elsevier Ltd.