An in-situ transient photo-induced voltage method to understand the PEC efficiency of C, N co-doped TiO2 photoanode

Under AM 1.5 G light intensity, the photocurrent density of TCN-1.5 is 4.06 mA cm−2 at 1.23V vs RHE in 1.0 M NaOH, which is ca. 2.08 times higher than that of the pristine TiO2. Besides, the in-situ TPV technology and its curve extrapolation analysis show the improvement of Jabs, ηsep and ηinj caused by changes of morphology and structure, and the product of the three factors above perfectly correspond to the increase in photocurrent density. [Display omitted] •TiO2 photoanode modified by C, N co-doping achieves efficient PEC performance.•The photocurrent density of TCN-1.5 is 4.06 mA cm−2 in 1 M NaOH under AM 1.5 G.•The efficiencies’ improvement in PEC process was tested by in-situ TPV technology.•A new in-situ method for PEC material design and fabrication is provided. Photoelectrocatalysis (PEC) is one of the most important green energy conversion technologies. During the development of PEC, the Jabs, ηsep and ηinj are challenges that hinder the performance enhancement of different kinds of photoanodes in PEC systems. As a stable, cheap and non-toxic PEC material, TiO2 is also limited by the above challenges. Here, a series of C, N co-doped TiO2 photoanodes were synthesized by hydrothermal method combined with a simple one-step thermal diffusion treatment. Under AM 1.5 G light intensity, the PEC performance of TCN-1.5 is 4.06 mA cm−2 at 1.23 V vs RHE in 1.0 M NaOH, which is ca. 2.08 times as high as the photocurrent density of the pristine TiO2. Especially, an in-situ transient photoinduced voltage (TPV) method was developed to measure the changes on efficiencies mentioned above: Jabs, ηsep and ηinj are improved by about 9.8 %, 24.9 % and 48.3 %, respectively, and their product is equal to the increase of photocurrent density. This work analyzes the improvement of efficiencies in the PEC process through in-situ characterization and opens up a new way for PEC material design and fabrication.