Hydrogen plasma-treated 1D/3D TiO2 nanorod array photoanode for efficient photoelectrochemical water splitting

Abstract The rutile phase titanium oxide (TiO2) based photoanode exhibits less energy conversion efficiency, as compared to anatase phase TiO2 photoanode. Enhancing the performance of the rutile phase TiO2 photoanode in a photoelectrochemical cell for water splitting is a significant challenge. In this study, we have grown the rutile phase 1D/3D nanorod array structure by using a one-step hydrothermal process. To enhance the surface properties of 1D/3D TiO2 nanorod array films, the as-grown films were treated in a hydrogen plasma atmosphere created using an electron cyclotron resonance (ECR) plasma system. The crystalline phases of the untreated and Hydrogen plasma treated films are confirmed by XRD and Raman studies. We found that, hydrogen plasma treatment creates Ti3+ sites and oxygen vacancies, leading to an increment in optical absorbance and reducing the band gap from 3.17 to 2.89 eV. Additionally, a significant enhancement in photocurrent density (0.369 mAcm−2 at 1 V versus Ag/AgCl) was observed in hydrogen plasma-treated 1D/3D TiO2 nanorod array photoanodes compared to untreated films (0.034 mAcm−2 at 1 V). The enhancement is attributed to the increase in carrier concentration induced by oxygen vacancy formation and the improved electron-hole pair separation. Further, the hydrogen plasma-treated 1D/3D TiO2 nanorod array photoanode exhibited high Photostability for long time duration.