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 Ta 3 N 5 photoanode, including the following: (1) Crystallographic-oriented growth minimizes the negative effect of electronic structure anisotropy of the Ta 3 N 5, 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 Ta 3 N 5 photoanode was dramatically negatively shifted to 0.4 V RHE, and thereby afforded a 0.82% half-cell solar-to-hydrogen efficiency.