Study of Poly (3,4-ethylenedioxythiophene)/MnO₂ as Composite Cathode Materials for Aluminum-Air Battery

Highlights: • Open-tunnel structure of MnO₂ catalysts were prepared by the hydrothermal method. • PEDOT was deposited on MnO₂/carbon paper by oxidative chemical vapor deposition. • PEDOT/α-MnO₂/10AA composite cathode shows the highest discharge performance. • The enhancement on discharge performance was due to the clear charge transfer. - Abstract: This study focuses on the development of the composite electrode materials for an aluminum-air battery and improving the oxygen reduction reaction (ORR) of the air electrode by matching alpha- and beta- manganese dioxide (MnO₂) with poly-(3,4-ethylenedioxythiophene) (PEDOT) conducting polymer. The catalyst powders of α-MnO₂ and β-MnO₂ are prepared by hydrothermal method with different precursors, while PEDOT conducting polymer is subsequently deposited on the screen-printed electrodes (MnO₂/carbon paper) by oxidative chemical vapor deposition (oCVD). Material characteristics of prepared MnO₂ powder and PEDOT layer are investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Raman scattering spectroscopy. The half-cell polarization curve test is found to be strongly depended on the crystalline phases of MnO₂. From experimental observations and a density functional theory (DFT) study, the conductivity of PEDOT/α-MnO₂ is found to be higher than PEDOT/β-MnO₂ contributed to structural effect mediated improvements in charge transfer. As a result, integrating the deposition of PEDOT on α-MnO₂/carbon paper as composite cathode is suitable for the use in aluminum-air battery