Insight into the High Proton Conductivity of One-/Two-Dimensional Cadmium Phosphites.

The study describes the synthesis and structural attributes of two new cadmium phosphites, [Cd{OP(O)(OH)H}(4,4'-bipy)] () and [Hpip][Cd(HPO)(HO)]·HO (). The structure of adopts a two-dimensional motif featuring alternate [Cd-μ-O] and [Cd-O-P-O]-cyclic rings, while the inorganic chains are held together by 4,4'-bipyridine. The presence of strong hydrogen bonding interactions between the appended HPO groups (O---O = 2.55 Å) provides a facile proton conduction pathway and results in a proton conductivity of 3.2 × 10 S cm at 75 °C under 77% relative humidity (RH). Compound comprises an anionic framework formed by vertex-shared [Cd-O-P-O]-cyclic rings, while the [Hpip] cations between the adjacent chains assist a well-directed O-H---O hydrogen-bonded network between coordinated water, lattice water, and phospite groups. The bulk proton conductivity value under conditions as in reaches 4.3 × 10 S cm. For both and , the proton conductivity remains practically unchanged under ambient temperatures (25-35 °C), suggesting their potential in low-temperature fuel cells.