Cellulose-based air-cathode loaded by in-situ hydrothermally synthesized NiFe2O4 for Al-air battery: Influence of surface chemistry on the electrochemical performance

Abstract

The influence of the cellulosic fabrics (CF) surface chemistry on hosting nickel ferrite (NF) and its application in Al-air battery was studied. CFs were modified with acrylate monomer bearing positively (COOCH<inf>2</inf>CH<inf>2</inf>N+(CH<inf>3</inf>)<inf>3</inf>Cl−) or negatively (-COO(CH<inf>2</inf>)<inf>3</inf>SO<inf>3</inf>K) charged functional groups at different degrees of graft-polymerization. NF was in-situ hydrothermally synthesized into the un/grafted-CF followed by in-situ polymerization of polyaniline (PANi) to enhance the electric conductivity nine orders of magnitude. This via altering the electron transport mechanism from the tunnelling to the variable-range hopping mechanism for CF-NF and PANied-CF-NF, respectively. XRD confirmed a single phase of Trevorite (NiFe<inf>2</inf>O<inf>4</inf>). SEM images showed a dense deposition of NF on the anionic fabrics and TEM images demonstrated the change of NF shape (nanorice – nanoctahedrons) and size (9–75 nm) as a function of the surface chemistry. Anionic ACs showed higher Ni+2 and Fe+3 uptake compared to the cationic ones as confirmed by ICP-OES and XPS. Cyclic voltammetry showed that NF reduced oxygen to water through 2 × 2 electron pathway. Electrochemical performance of ACs showed a good correlation with the NF content to an extent. Highest current density (4 mA/cm2) and discharge time (13.8 h) were obtained from anionic AC compared to 1.7–2.5 h for blank and cationized ACs, respectively.