Construction of nanorod-shaped TiO2/Cu3N p–n heterojunction for efficient visible-light hydrogen evolution

Abstract

Developing highly efficient and low-cost photoelectrocatalyst for H₂ evolution under visible-light irradiation is a key topic in the areas of energy and environment. In this work, we designed and deposited p-type semiconductor Cu₃N onto 1D n-type rutile TiO₂ nanorod array by the magnetron sputtering method. The formed TiO₂/Cu₃N p–n heterojunction not only exhibits a narrowed band gap from 3.09 eV for TiO₂ to 2.01 eV for TiO₂/Cu₃N but also expands the light-response from UV to visible-light region. In addition, the lifetime, separation and transfer of the photogenerated electron–hole pairs are efficiently prolonged and improved due to the build-in electric field at the interface of the TiO₂/Cu₃N p–n heterojunction. As a result, the photocurrent density under >420 nm visible-light irradiation is enhanced for about 14.12 times, from −0.33 mA cm⁻² for TiO₂ to −4.66 mA cm⁻² for TiO₂/Cu₃N at −0.97 V vs. RHE (reversible hydrogen electrode). Furthermore, the constructed TiO₂/Cu₃N heterojunction shows stable PEC H₂ evolution performance, with the H₂ production rate reaching 6.98 μmol cm⁻² h⁻¹ under >420 nm visible-light irradiation. Our results suggest that the construction of nontoxic p–n heterojunction with suitable band gap should be a promising strategy to improve the photoelectrocatalytic performance of TiO₂ and should be applied in other photoelectrocatalysts.