Structure and Facile Synthesis of Proton-Conducting [Fe(CN)6]3- Bridged Cd-Complex

Proton-conducting materials are a key component of proton exchange membrane fuel cells (PEMFCs) and the advantage of clear structural information in crystal materials offers a pathway for the investigation of the proton-conducting mechanism and pathway. In this work, a new Cd2+ coordination polymer material (compound 1) with the formula {[Cd-3(bipy)(3)(H2O)(4)][Fe(CN)(6)](2)center dot 2H(2)O center dot 2(bipy)}(n) was successfully synthesized by a solution diffusion method and its proton conduction ability was further determined. Crystal structure analysis confirms the coordination of [Fe(CN)(6)](3-), 4,4'-bipyridine, and H2O molecules to Cd2+ in the three dimensional structure of compound 1. Also, we confirmed that compound 1 of 500-800nm particle size could be synthesized on a large scale by a facile stirring method. Protonconductivity analyses revealed that compound 1 shows a water-mediated proton conduction behaviour because the conductivity increased apparently with the increase of relative humidity. Further investigation shows that the highest proton-conductivity of 8.36 x 10(-4) S cm(-1) was observed at 60 degrees C and 95% relative humidity, and the mechanism analysis suggests a Vehicle mechanism exists in the proton conduction process of compound 1.