Ultrafast proton transport via two-dimensional vermiculite membranes regulated by thermal compression

Conventional proton-exchange membranes (PEMs) like Nafion face conductivity limitations (~ 0.1 S·cm⁻¹). This study explores thermal compression of vermiculite membranes (VMs) as a potential alternative. Controlled thermal compression at 300–500 °C reduced interlayer spacing and improved nanosheet alignment, which make nanochannel dimensions approaching the critical scale for ballistic transport. Consequently, proton conductivity is significantly enhanced. The membrane treated at 400 ℃ achieved a proton conductivity of 1.77 S·cm⁻¹ at 90 °C—far exceeding Nafion under identical conditions. However, temperatures at 500 °C appeared to induce crystallization, increasing proton transport barriers. This suggests that there is a trade-off between the interlayer spacing and the crystallinity. These findings indicate that thermally engineered 2D membranes could offer new pathways for high-conductivity PEM design.