Band structure engineering and defect control of Ta3N5 for efficient photoelectrochemical water oxidation

Ta 3 N 5 is a promising photoanode material with a theoretical maximum solar conversion efficiency of 15.9% for photoelectrochemical water splitting. However, the highest applied bias photon-to-current efficiency achieved so far is only 2.72%. To bridge the efficiency gap, effective carrier management strategies for Ta 3 N 5 photoanodes should be developed. Here, we propose to use gradient Mg doping for band structure engineering and defect control of Ta 3 N 5 . The gradient Mg doping profile in Ta 3 N 5 induces a gradient of the band edge energetics, which greatly enhances the charge separation efficiency. Furthermore, defect-related recombination is significantly suppressed due to the passivation effect of Mg dopants on deep-level defects and, more importantly, the matching of the gradient Mg doping profile with the distribution of defects within Ta 3 N 5 . As a result, a photoanode based on the gradient Mg-doped Ta 3 N 5 delivers a low onset potential of 0.4 V versus that of a reversible hydrogen electrode and a high applied bias photon-to-current efficiency of 3.25 ± 0.05%.