Mg-Doped Hematite Nanoparticle Arrays Coated with CoPi Thin Films for Solar Water Oxidation

As a promising candidate for photoelectrochemical water decomposition, α-Fe 2 O 3 has been plagued by low actual quantum efficiency and weak stability. In this work, we prepared an α-Fe 2 O 3 photoanode with Mg doping and cobalt-hydroxyl-phosphate (CoPi) coating. Compared to α-Fe 2 O 3, the CoPi/Mg–Fe 2 O 3 photoanode exhibited remarkably enhanced activity of photoelectrochemical water splitting. The photocurrent density of the CoPi/Mg–Fe 2 O 3 photoanode was 1.30 mA cm –2 at 1.23 V vs RHE, which was around 3.51 times higher than that of α-Fe 2 O 3 (0.39 mA cm –2 ). In addition, the CoPi/Mg–Fe 2 O 3 photoanode demonstrated good stability, and the photocurrent density produced by the CoPi/Mg–Fe 2 O 3 photoanode did not decrease significantly after 24 h of light irradiation. The efficiencies of bulk charge separation and surface charge injection of the CoPi/Mg–Fe 2 O 3 photoanode were greatly increased through Mg doping and CoPi coating, which significantly improved its performances of photochemical water splitting.