Structural and electrical properties of novel phosphate based composite electrolyte for low-temperature fuel cells

Lowering the operating temperature of solid-electrolyte based fuel cells is an attractive approach to achieve highly efficient energy conversion devices for the next-generation demands. The present work aims to develop proton-conducting electrolyte materials for low-temperature fuel cells. In this regard, a host matrix of gadolinium-doped cerium pyrophosphate (CGP) has been reinforced by cesium pentahydrogen diphosphate (CPP) to deliver dense electrolyte material. The composite electrolyte materials were formulated with different compositions and examined for the phase purity, sinterability, functional group, and electrical conductivities. It was found that the reinforcement by CPP assisted formation of a core-shell structure, which accelerated the proton migration by the acidic dissolution of proton into the shell. This acidic dissolution fastens the kinetics of hydrolysis of the electrolyte resulting in a maximum ionic conductivity of about 9 mS cm−1 at 110 °C under humidified air (pH2O = 0.12 atm) atmosphere. Besides, a maximum ionic conductivity of 0.8 mS cm−1 was also achieved at 230 °C under dry air atmosphere. Moreover, the entire composite electrolytes realized a remarkable densification (>95%) which substantiate the practical suitability of the presented materials to be used for the low-temperature fuel cells.