Charge Transport in Nanoporous LaMnO ₃ Thin Films

The development of future energy conversion devices passes inevitably through the improvement of the mass transport and oxygen exchange of the oxygen electrode. Herein, we show how nanoporosity can be used to enhance reducibility and thereby oxygen evolution in LaMnO ₃ and how it influences the electronic transport in the material. An ordered nanoporous LaMnO ₃ thin film (thickness 80 nm, pore size 25 nm) was prepared by the sol–gel approach using block copolymer templating. At high temperature, the Mn 2p X‐ray photoelectron spectroscopy (XPS) showed increased reduction of Mn to Mn ³⁺ and Mn ²⁺ for nanoporous LaMnO ₃ compared to its dense counterpart at 400 °C, indicating larger release of oxygen due the high surface‐to‐volume ratio of the material. In turn, the electrical resistivity of the material increased by 10 times and the activation energy of the electronic conductivity by 15%, as shown by finite element method (FEM) simulations and impedance spectroscopy analyses. This effect was attributed both to the tortuous path induced by the nanoporosity and to the spontaneous electronic conductivity decrease, i.e., hole consumption, consequent to the extensive material reduction.