Phosphorylated cellulose based macromolecular films with high charge density for high-performance moisture-powered generators.

As a renewable polysaccharide macromolecule, cellulose has attracted significant attention in green moisture-powered generators due to its widespread availability and excellent hydrophilicity. However, the performance of cellulose macromolecules in humidity-driven power generation is constrained by inadequate protonation and ion diffusion properties. In this work, a highly charged cellulose macromolecule with a charge density of 4.02 mmol/g was obtained through one-step phosphorylation using the urea/phosphate system under optimal conditions of 170 °C for 30 min. Phosphorylation introduces phosphate ester groups onto the anhydroglucose units (AGUs) of the cellulose backbone, yielding a degree of substitution (DS) of 0.65. A cellulose membrane-based moisture-powered generator (P-MEG) was developed via vacuum filtration. Meanwhile, the enhanced hydrophilicity resulting from phosphorylation promotes both moisture absorption and ion diffusion within the film. The P-MEG demonstrated an average output voltage of 0.55 V (maximum 0.61 V) and a short-circuit current of ~12 μA under 95% relative humidity, with a maximum output power of 1.07 μW at a load resistance of 25 kΩ. The device maintained continuous voltage output for more than 7 h. The surface charge density and hydrophilicity of cellulose are critical factors in enhancing the voltage output performance of moisture-powered generators. Phosphorylation modification of cellulose is a green and effective approach to improving its surface charge density and hydrophilicity for high-performance energy harvesting applications.