Construction of cellulose-based dual-gradient heterogeneous bilayer membranes with optimized directional moisture transport property for enhancing moisture-electricity generation.

Moisture-electricity generation (MEG) offers a promising strategy for sustainable energy conversion by harvesting ambient moisture to generate electricity. However, cellulose-based MEGs (CMEGs) are limited by inefficient proton migration and disordered moisture transport. To address these issues, we propose a dual-gradient heterogeneous bilayer cellulose-based membrane (CA@CF/CANPF) for Bi-CMEGs. The pore size gradient regulates water adsorption and diffusion, effectively guiding directional transport within the membrane, while the gradient of oxygen-containing functional groups improves hydrophilicity and facilitates ion exchange, accelerating proton migration. This Bi-CMEGs design achieves an open-circuit voltage of approximately 665.2 mV, a short-circuit current of 11.2 μA/cm and an effective power density of 1.24 μW/cm, demonstrating excellent adaptability and stability across varied temperature and humidity conditions. Compared to recent advancements in CMEGs, the dual-gradient structure significantly enhances moisture transport and proton migration, overcoming key efficiency and scalability limitations. Notably, an amplified voltage of approximately 2516.7 mV is achieved by integrating the Bi-CMEG units in series, which is sufficient to directly power an LED for over 6 h under typical laboratory conditions. This work emphasizes the dual-gradient structure of Bi-CMEG, providing an efficient and unique design concept for sustainable cellulose-based moisture-electricity generation devices.