Nature-inspired solid-state proton diode membrane for high-performance force-electric conversion.

Bioinspired ion channel membranes with ultrafast and directional transport capabilities, akin to biological protein-based channel, are crucial for various energy and sensing applications. However, controlling highly active protons and advancing practical applications, which are often constrained by the use of liquid-based electrolyte, remains major challenges. Here, we report a bioinspired solid-state diode membrane with ultrafast and highly rectified proton transport, achieved through the hybridization of graphene oxide (GO) and Cu-coupled bacterial cellulose (BC-Cu) with inherent gradient in water content. The asymmetric proton transport pathways and potential differences between the two-dimensional GO interlayers and one-dimensional BC network create a stable diode effect, achieving exceptionally high rectification ratios of approximately 125. Theoretical calculations reveal that the distinct ion transport pathways and interfacial potential barrier disparities constitute the fundamental mechanism underlying the highly rectified ionic current. In particular, the enhanced proton transport greatly facilitates the force-electric conversion, allowing the diode membrane to accurately respond to external pressure. Our bioinspired approach to fabricate all-solid-state proton diodes hold great potential for next-generation solid-state rectification systems, with promising applications in areas such as self-powered pressure sensing and neuromorphic computing.