Low-temperature fuel cells using proton-conducting silicate solid electrolyte†

Fuel cells utilizing proton-conducting oxides generally require operating temperatures of at least 500 °C, limiting their applicability in low-temperature fuel cells. Herein, we report flexible solid electrolytes, H_0.37Al_1.67Mg_0.35Fe_0.11Si_3.9O₁₀(OH)₂(H₂O)_2.6, fabricated with monolayer silicate nanosheets, which exhibit high proton conductivity (0.005–0.02 S cm⁻² at 90 °C) and superior hydrogen gas barrier properties compared with Nafion. The H₂ fuel cells fabricated using this membrane achieved a maximum current density of 1080 mA cm⁻² and a maximum power density of 264 mW cm⁻² at 90 °C. Furthermore, the cell operates effectively across a wide temperature range (−10–140 °C). It has the potential to become a next-generation fuel cell that addresses the challenges of both conventional low-temperature and high-temperature fuel cells.