Polypyrrole-coated nanocellulose for solar steam generation: A multi-surface photothermal ink with antibacterial and antifouling properties

Solar energy-based steam generation holds immense potential to tackle the problem of 1.1 billion people lacking access to freshwater and 2.7 billion experiencing freshwater scarcity at least one month a year. Efficient, portable, and universal photothermal materials are required for popularity of solar-driven evaporation systems. Herein, a facile one-pot process based on solution-processed vapor phase polymerization is adopted to fabricate polypyrrole-coated cellulose nanocrystals (CNC-PPy). The CNC-PPy dispersed in water is used as an ink (CNC-PPy ink) to create photothermal layers. The developed ink is readily laminated on diverse substrates utilizing a common paintbrush that firmly attached without any delamination after drying. The optimized cellulose membrane (6 coating cycles) presents an excellent evaporation rate of 1.96 Kg m⁻² h⁻¹ with corresponding light-to-vapor efficiency of 88.92 % at 1 sun. In addition, the CNC-PPy display excellent antibacterial and antifouling properties in powder and laminated forms against E. coli and S. aureus.