Photoelectrochemical water-splitting over a surface modified p-type Cr2O3 photocathode

Abstract

Cr₂O₃ is a p-type semiconductor with a negative conduction band minimum position suitable for photocathodic H₂ generation. Therefore, Cr₂O₃ is a candidate photocathode material for photoelectrochemical (PEC) water-splitting. However, Cr₂O₃ has not yet been applied for the purpose of H₂ generation because the efficiency and stability of the photocurrent generated by a Cr₂O₃ electrode are poor, due to high defect and vacancy concentrations. In the present work, the Cr₂O₃ surface was modified with n-type TiO₂ after which Pt particles were deposited to catalyse H₂ production. The TiO₂ overlayer passivated the Cr₂O₃ surface states that otherwise cause deleterious interactions with the Pt particles. This layer also improved charge separation from the conduction band of Cr₂O₃ to the Pt co-catalyst, by forming a p–n junction. As a result of the TiO₂ insertion, the cathodic photocurrent resulting from light absorption by Cr₂O₃ was enhanced and stabilized. This represents the first-ever use of Cr₂O₃ as a light-absorbing material in a multi-layered electrode to accomplish PEC water-splitting for H₂ generation.