Construction of CdS/Ti-Nb-O composite photoanode with favorable optical absorption and charge transfer for dramatically boosted photoelectrochemical water splitting

Abstract

Rational design and construction of highly effective Ti-based photoanodes with advantageous structures are crucial to enhance photoelectrochemical (PEC) water splitting. In this work, we reported a CdS/Ti-Nb-O composite photoanode with satisfactory charge transfer and optical absorption for dramatically boosted PEC performance, which was constructed by bulk-phase Nb-doping synergistically with CdS quantum dots (QDs) sensitization of Ti-based oxide nanostructures. The composite system exhibited a remarkable photocurrent density of 16.11 mA cm-2, which was 34 times higher than pure TiO2 (0.47 mA cm-2). The electron lifetime was substantially increased and the solar-to-hydrogen (STH) conversion efficiency could be as high as 9.45%. Bulk-phase Nb-doping improved the conductivity of Ti-Nb-O, which enabled speedy and sustained charge separation in the composite-electrolyte solid-liquid interface. Meanwhile, CdS sensitization extended light absorption from 410 nm to 640 nm, thereby generating more photogenerated carriers. Simultaneously, Nb-doping negatively shifted the valence band (VB) and conduction band (CB) of Ti-Nb-O, which made the energy band more compatible with CdS. And the well-matched energy band structures of CdS and Ti-Nb-O not only improved separation-transfer properties of photogenerated electrons and holes but also increased overall optical absorption property of the composite system. This work involved dual-regulation charge separation strategy through bulk-phase doping synergetically with QDs sensitization may contribute to constructing high-efficient Ti-based photoanodes for PEC water splitting.