Inhibitive effect of quaternary ammonium-type surfactants on the self-corrosion of the anode in alkaline aluminium-air battery

The most serious drawback of aluminium-air batteries with aqueous alkaline electrolytes is parasitical hydrogen evolution reaction. It is essential to identify an effective electrolyte additive for suppressing the self-corrosion of the aluminium anode. This work reports the inhibition effects of three quaternary ammonium-type surfactants, cetyl trimethyl ammonium bromide (CTAB), dihexadecyl dimethyl ammonium bromide (DDAB) and dodecyl dimethyl benzyl ammonium bromide (DDBAB), as corrosion inhibitors for the aluminium-air battery anode in 4 mol L-1 NaOH solution. Hydrogen collection technique, potentiodynamic polarization, electrochemical impedance and surface analysis are used to evaluate the corrosion inhibition properties of the additives. The results indicate that all the additives show anticorrosion efficiency in the order of DDBAB > CTAB > DDAB. The molecular structures of the surfactants are simulated by the density functional theory method in order to clarify the correlation between inhibition effect and the molecular structures. The presence of surfactants not only increases the voltage of the aluminium-air battery under galvanostatic discharge, but also increases the specific capacity markedly. Finally, the inhibition mechanism of cationic surfactants is proposed, and the reasons for the different inhibition performance of these additives are analysed.