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 TiO 2 . Besides, the in-situ TPV technology and its curve extrapolation analysis show the improvement of J abs , η sep and η inj caused by changes of morphology and structure, and the product of the three factors above perfectly correspond to the increase in photocurrent density. • TiO 2 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 J abs , η sep and η inj are challenges that hinder the performance enhancement of different kinds of photoanodes in PEC systems. As a stable, cheap and non-toxic PEC material, TiO 2 is also limited by the above challenges. Here, a series of C, N co-doped TiO 2 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 TiO 2 . Especially, an in-situ transient photoinduced voltage (TPV) method was developed to measure the changes on efficiencies mentioned above: J abs , η sep and η inj 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.