Ordered Proton Transport Channels in a Layered Host–Guest Crystal for High-Performance Fuel Cells

Developing solid electrolytes with high intrinsic proton conductivity over a broad temperature range is crucial for proton exchange membrane fuel cells. We report a new layered cadmium chlorophosphate crystal, (C₃N₂H₅)[CdCl(H3/2PO₄)]₂ (CdClPO₄-ImH), featuring highly ordered one-dimensional proton transport channels formed by host-guest synergy between imidazolium cations and inorganic layers. Structural and theoretical analyses revealed a continuous hydrogen-bonding network that promotes efficient proton hopping. The material shows excellent proton conductivity from -20 to 90 °C, reaching 2.57 × 10⁻² S cm⁻¹ at 90 °C and 95% relative humidity (RH). An undoped intrinsic membrane delivered a peak power density of 104 mW cm⁻² in a H₂/O₂ fuel cell.