Developing hematite homojunction with titanium and magnesium dopants for photocatalyzing water oxidation

Developing homojunction can promote preferable charge cascade and improve electron transfer. Doping different metals in hematite is able to create pn homojunction, which cannot only increase electrical conductivity but also accelerate oxidation evolution kinetics. In this study, titanium and magnesium are separately doped in the first and second layers of hematite to create pn homojunction and to improve the photocatalytic ability toward water oxidation. The ratio of titanium and magnesium dopants incorporated in hematite is optimized regarding to the morphology, optical property and electrochemical feature. The highest photocurrent density of 2.99 mA cm(-2) at 1.60 VRHE is obtained for the hematite homojunction photoanode prepared using magnesium to titanium ratio of 30-70. This optimized hematite homojunction photoanode also shows the smallest charge transfer resistance, the highest carrier density and the longest electron lifetime. Also, nearly no decay on the photocurrent density is also achieved for the optimized hematite homojunction photoanode after 3600 s continuous light illumination. It is verified that the ratio of two dopants in hematite plays important roles on the photocatalytic ability toward water oxidation, since the hematite homojunction photoanode with the magnesium to titanium ratio of 50% only presents one-half of the photocurrent density and one two thousand of the carrier density of those for the optimized photoanode. It is expected to establish more efficient hematite photocatalysts via creating more beneficial homojunction with suitable dopants. (c) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Automated summary

Doping titanium and magnesium in hematite can enhance its photocatalytic ability for water oxidation. By optimizing the dopant ratio, the optimized hematite homojunction photoanode exhibits the highest photocurrent density, smallest charge transfer resistance, highest carrier density, and longest electron lifetime.