Effect of mixed-valence of manganese on water oxidation activity of La1-xCaxMnO3 (0 < x < 1) solid solutions

The water oxidation reaction is one of the crucial process involves 4e- and 4H+ transfer, which causes a high energy barrier and makes the water-splitting process a slow kinetic reaction. Herein, we have systematically observed the water oxidation activity of La1-xCaxMnO3 (0< x < 1) solid solutions by tuning the valence of Mn ion through selective substitution of La3+ with Ca2+. With increasing Ca concentration in La1-xCaxMnO3 solid solutions, the water oxidation activity increases up to x = 0.5 and then decreases. Mixed -valence of Mn generated due to substitution of La3+ with Ca2+, which leads to the double exchange mechanism. This could results in high electrical conduction and a faster electron transfer rate because of the rapid charge exchange between Mn3+ and Mn4+ ions, which pinpoints the reason behind the enhanced oxygen evolution activity. Our findings will be a promising way to relate the Mn mixed-valence with its catalytic activity to design and development of efficient water oxidation catalysts.(c) 2023 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Automated summary

The water oxidation activity of La1-xCaxMnO3 solid solutions was systematically observed by tuning the valence of Mn ion. It was found that the water oxidation activity increases up to x = 0.5 and then decreases with increasing Ca concentration. This is due to the double exchange mechanism caused by the mixed-valence of Mn, which enhances the electrical conduction and electron transfer rate, leading to enhanced oxygen evolution activity. This finding provides useful insights for designing and developing efficient water oxidation catalysts.