Oriented Growth of Sc-Doped Ta3N5 Nanorod Photoanode Achieving Low-Onset-Potential for Photoelectrochemical Water Oxidation

Developing photoanodes that can split water with low (or even without) externally applied bias is a critical challenge for achieving efficient solar-driven photoelectrochemical water oxidation. Here, we proposed a flux-assisted oriented crystal growth route to minimize the drawbacks of Ta3N5 photoanode, including the following: (1) Crystallographic-oriented growth minimizes the negative effect of electronic structure anisotropy of the Ta3N5, facilitating the directional fast charge transfer in having lighter carrier effective mass of (b,c)-axes directions. (2) Reducing crystal defects suppressed surface recombination of carriers and released the surface Fermi level pinning effect. (3) Increment of oxygen-impurity electron donor by Sc doping improved the electrical conductivity, promoting the bulk charge separation and transfer. Specifically, the onset potential of Ta3N5 photoanode was dramatically negatively shifted to 0.4 VRHE, and thereby afforded a 0.82% half-cell solar-to-hydrogen efficiency.