Ionic transport in aluminum polyphosphate hydrogels

Transparent aluminum polyphosphate hydrogels were synthesized, aged under different humidity conditions and characterized by NMR and complex impedance spectroscopy in order to elucidate the prevailing ionic transport mechanism. The ionic conductivity of these gels approaches 10−2 S cm−1 at room temperature in an ambient with relative humidity of approximately 70%. The ionic conduction mechanism is concluded to be predominantly protonic and its interpretation may address important aspects of the Grotthuss process, such as the role of geometrical constrains that may hinder protonic transport. The hydrogels, which may be useful solid electrolytes, have good adherence to many substrates and can be molded or transformed into self-standing films.