Heteroatom Doping Strategy for Establishing Hematite Homojunction as Efficient Photocatalyst for Accelerating Water...

Hematite (α-Fe₂ O₃ ) is one of the promising photocatalysts for water oxidation, owing to its stable, abundant and visible-light responsive features. Enhancing electrical conductivity and accelerating oxidation evolution kinetics are expected to improve photocatalytic ability of hematite toward water oxidation. In this work, strategies of doping heteroatoms and developing pn homojunction are adopted to enhance the photocatalytic ability of hematite electrodes. The Ti and Mg dopants are separately incorporated in two layers of hematite electrodes via two-step hydrothermal reaction and one-step annealing process. The effect of regrowth time for synthesizing Mg-doped hematite on the photoelectrochemical performance of Mg-doped and Ti-doped hematite (Mg-Fe₂ O₃ /Ti-Fe₂ O₃ ) electrode is studied. The size of rod-like structure and gaps in-between play important roles on the photocatalytic ability of Mg-Fe₂ O₃ /Ti-Fe₂ O₃ . The optimized Mg-Fe₂ O₃ /Ti-Fe₂ O₃ electrode is prepared by using merely 10 min for synthesizing the Mg-doped hematite top layer, which shows the highest photocurrent density of 2.83 mA/cm² at 1.60 V_RHE along with the highest carrier density of 5.89×10¹⁶  cm^-3 and the smallest charge-transfer resistance. This largely improved photoelectrochemical performance is attributed to the more donor generation with heteroatom-doping and more efficient charge cascade with homojunction establishment. Other p-type metals are encouraged to dope in hematite as the second layer to couple with the n-type Ti-doped hematite for developing efficient pn homojunction and improve the photocatalytic ability of hematite in the near future.