Proton Dynamics of CsH₂PO₄ Solid Acid using ¹H and ³¹P Magic Angle Spinning Nuclear Magnetic Resonance (MAS-NMR)

This study investigated hydrogen-bonded CsH₂PO₄ (CDP) solid acid using ¹H and ³¹P high-resolution nuclear magnetic resonance (NMR). Below the superprotonic phase transition temperature, the temperature dependence of the H NMR spectra was observed with two different hydrogen-bonded networks in the CDP structure. The systematic evolution of the lineshape with temperature dependence indicates hydrogen hopping in the chemical structure of hydrogen-bonded networks in a solid acid lattice. The proton conduction under two types of hydrogen-bonds—interchain and intrachain—in CsH₂PO₄ in the chemical environments of PO₄ tetrahedra is discussed.