Correlation Between Conductivity and Oxygen Evolution Reaction Activity in Perovskite Oxides CaMnO3-δ, Ca0.5Sr0.5MnO3-δ and SrMnO3-δ
2025
Amara Martinson | Mandy Guinn | Peter Mortensen | Ram Krishna Hona
The perovskite oxides CaMnO3-&delta:, Ca0.5Sr0.5MnO3-&delta:, and SrMnO3-&delta: were synthesized in air using a solid-state method, and their structural, electrical, and electrocatalytic properties were studied in relation to their oxygen evolution reaction (OER) performance. Iodometric titration showed &delta: values of 0.05, 0.05, and 0.0, respectively, indicating that Mn is predominantly in the 4+ oxidation state across all materials, consistent with prior reports. Detailed characterization was performed using X-ray diffraction (XRD), scanning electron microscopy (SEM), iodometric titration, and variable-temperature conductivity measurements. Four-point probe DC measurements revealed that CaMnO3-&delta: (&delta: = 0.05) has a semiconductive behavior over a temperature range from 25 °:C to 300 °:C, with its highest conductivity attributed to polaron activity. Cyclic voltammetry (CV) in 0.1 M KOH was employed to assess OER catalytic performance, which correlated with room-temperature conductivity. CaMnO3-&delta: exhibited superior catalytic activity, followed by Ca0.5Sr0.5MnO3-&delta: and SrMnO3-&delta:, demonstrating that increased conductivity enhances OER performance. The conductivity trend, CaMnO3-&delta: >: Ca0.5Sr0.5MnO3-&delta: >: SrMnO3-&delta:, aligns with OER activity, underscoring a direct link between electronic transport properties and catalytic efficiency within this series.
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