Tunable Photo‐Electrochemistry of Patterned TiO₂/BDD Heterojunctions

Abstract

Abstract Heterojunctions are especially attractive for photo‐electrocatalytic applications if both high‐performance photo and electrocatalysts are employed for their construction. Herein, a p–n heterojunction is synthesized using uniform patterns of p‐type boron doped diamond (BDD) and an n‐type anatase TiO 2 film. The exposure ratios of the BDD patterns are varied to tune the photo‐electrocatalytic abilities of this heterojunction. A heterojunction with a BDD exposure ratio of 20% exhibits a photocurrent density of 0.63 mA cm −2 , which is 2.86‐fold higher than that obtained on a BDD film and 1.91‐fold higher than that obtained on a TiO 2 film coated on a BDD film. It completely degrades methyl orange within 4 h, following the application of a 2.5 V bias potential, while the degradation efficiency on the BDD film and the TiO 2 film is 56% and 45%, respectively. As confirmed by electron spin resonance spectroscopy, an accelerated production rate of •OH radicals is realized on this heterojunction. It originates from a synergistic effect between the BDD patterns that act as an ultra‐microelectrode array with a TiO 2 /BDD p–n heterojunction as well as facilitated charge separation in a lateral direction. This TiO 2 /BDD patterned heterojunction is thus promising as a new photo‐electrocatalyst for various catalytic applications.