Exploring the potential of calcined nanolayered manganese oxides for water-oxidation reaction

Abstract

Large-scale electrochemical and photochemical hydrogen production methods from water splitting are limited by the water-oxidation reaction (WOR). This study investigates the influence of calcination temperatures on the WOR efficiency of layered Mn oxides, which are known for their stability and high catalytic activity. The Mn oxides were synthesized via thermal decomposition of KMnO4 and characterized using various techniques including scanning electron microscopy, high-resolution transmission electron microscopy, X-ray diffraction, thermal gravimetric analysis, and Raman spectroscopy. The results indicate that even after calcination at high temperatures (≥400 °C), layered Mn oxides remain effective catalysts for WOR. Notably, the calcined sample at 800 °C in cerium (IV) ammonium nitrate at concentrations of 0.30 M shows maximum turnover frequency and turnover number of 6.7 × 10−6/s and 8.6 × 10−3 mol (O2)/mol (Mn) (for 1300 s), respectively.