Nanostructured boron doped diamond enhancing the photoelectrochemical performance of TiO2/BDD heterojunction anodes

Photoelectrochemical (PEC) water splitting provides a promising way for development of sustainable methods of hydrogen generation and water treatment without chemicals. In this paper, we report on the development of a unique PEC electrode consisting of nanostructured p-type boron doped diamond (BDD) layers covered by n-type TiO2 thin film. The influence of nanostructuring and boron doping level, as well as the thickness of TiO2 film on PEC properties, was investigated. As-grown and plasma-nanostructured BDD thin films with two doping levels (B/C =1 000 ppm and 10 000 ppm in the gas phase) were utilized as substrates for deposition of 20, 100 and 500 nm TiO2 layers using RF magnetron sputtering. The highest photocurrent (60 mu A/cm(2) and 3.2 mA/cm(2) at 0 and 2 V vs Ag/AgCl respectively) was obtained in the case of structured BDD electrode with B/C ratio in gas phase 1 000 ppm, covered by a 500 nm thick TiO2 layer. The experiment confirmed the favorable impact of both nanostructuring and p-n junction, contributing to the hole injection.