Structure-dependence of electrical conductivity and electrocatalytic properties of Sr2Mn2O6 and CaSrMn2O6

Remarkable enhancement of the electrical conductivity and electrocatalytic activity is demonstrated as a result of the transformation of crystal structure between Sr2Mn2O6 and CaSrMn2O6. The structure of Sr2Mn2O6 is known to consist of dimeric units of face-sharing MnO6 octahedra. Whereas, CaSrMn2O6 contains individual octahedra, connected to each other through corner-sharing. Herein we show that the changes in the crystal structure result in significant improvement of the electrical conductivity, by five orders of magnitude, for CaSrMn2O6, compared to Sr2Mn2O6. Variable temperature conductivity studies from 25-800 degrees C indicate semiconducting properties for both compounds, where the enhanced conductivity of CaSrMn2O6 persists in the entire temperature range. The electrocatalytic activity of both compounds toward oxygen evolution reaction (OER) has also been investigated, indicating superior OER activity of CaSrMn2O6 compared to Sr2Mn2O6. A pronounced improvement in the onset potential and kinetics of OER is observed for CaSrMn2O6. These studies demonstrate an important correlation between crystal structure, electrical conductivity and electrocatalytic properties.