Mesoporous lanthanum phosphate nanostructures containing H3PO4 as superior electrolyte for PEM fuel cells

Abstract

Mesoporous lanthanum phosphate nanostructures, involving diverse shaped LaPO₄ nanostructures synthesized in EG solution and dandelion-like LaPO₄·0.5H₂O nanospheres obtained in aqueous solution, have different surface areas and pore volumes for various nanostructures. Lanthanum phosphate containing H₃PO₄ were prepared by impregnating as-obtained lanthanum phosphate nanostructures in phosphoric acid solution, which showed different proton conductivities for diverse morphologies of lanthanum phosphate and different contents of H₃PO₄. Among them, sphere-shaped LaPO₄ nanostructures containing 5 wt% H₃PO₄ (s-LaPO₄–5 wt% PA) showed promising proton conductivity of around 10⁻² S cm⁻¹ at 120–180 °C and 20% RH. Moreover, the pellet pressed by s-LaPO₄–5 wt% PA powder could act as the electrolyte of a proton exchange membrane fuel cell (PEMFC) and exhibit higher performance (maximum power density of 84.0 mW cm⁻²) than Nafion 115 membrane at 180 °C and under 20% RH. In addition, the stability of the MEA electrolyte and the duration of a single cell based on s-LaPO₄–5 wt% PA were also tested.