Photoelectrochemical Manifestation of Photoelectron Transport Properties of Vertically Aligned Nanotubular TiO 2 Photoanodes

A simple photoelectrochemical method was proposed to quantitatively evaluate the electron transport process of photoelectrocatalytic oxidation of water at vertically aligned nanotubular TiO 2 photoanodes. The photoelectrocatalysis reaction resistance ( R = k / J sph + R 0 = R I + R 0 ) was measured and used to express the electron transport characteristics of a nanotubular TiO 2 electrode. The overall resistance was found to consist of a variant ( R I ) and an invariant component ( R 0 ). R I was found to be inversely proportional to the saturation photocurrent and it depends on the experimental conditions. The proportional constant, k , represents the minimum applied potential bias required to remove 100 % of the photogenerated electrons from the photocatalyst layer and was found to be independent of the anodization time. The invariant component of the resistance ( R 0 ) is an inherent property of the semiconductor photocatalyst that represents the sum of Ohmic contact impedance at the conducting substrate/TiO 2 interface and crystalline boundary impedance. The magnitude of R 0 linearly increased with anodization time. The real saturated photocurrent density ( J real‐sphd ) was found to be independent of R 0 indicating that the electron collection efficiency is independent of the nanotube length.