Irregularly Shaped Mn2O3 Nanostructures with High Surface Area for Water Oxidation

Water oxidation is an energy-consuming, four-electron-transfer reaction and is essential for solar fuel production from water. Catalysts based on precious metals such as RuO2 and IrO2 show high efficiency for oxygen evolution reaction. However, these catalysts are less abundant and expensive. To date, earth-abundant water oxidation catalysts still exhibit less activity for water oxidation. Herein, we report the synthesis of high surface area Mn2O3 nanomaterials for an efficient photocatalytic water oxidation catalyst. The synthesis process involves three simple steps. In the first step, CaMnO3 is synthesized by the citrate-gel method. In the second step, CaMnO3 is transformed into freestanding layers of epsilon-MnO2 by selective removal of Ca2+. In the third step, these layers are converted into irregularly shaped two-dimensional Mn2O3 flakes (AD-Mn2O3) by calcination at 550 degrees C. These AD-Mn2O3 nanostructures show 4 times higher surface area (127 m(2) g(-1)) when compared to the irregularly shaped Mn2O3 nanoparticles (CG-Mn2O3) synthesized by the citrate-gel method at the same temperature. The AD-Mn2O3 nanostructures show super hydrophilicity with a contact angle of zero degree. This material exhibits excellent photocatalytic water oxidation activity with a turnover frequency of 1.53 x 10(-3) s(-1), which is twice the activity shown by CG-Mn2O3. This study can help in developing an earth-abundant, cost-effective, efficient catalyst for overall water splitting.

Automated summary

This study reports the synthesis of high surface area Mn2O3 nanomaterials as an efficient photocatalytic water oxidation catalyst. The AD-Mn2O3 nanostructures exhibit excellent water oxidation activity, showing super hydrophilicity and a higher surface area compared to conventional Mn2O3 nanoparticles. The research aims to develop an earth-abundant, cost-effective, and efficient catalyst for overall water splitting.