Semicarbonized Subwavelength-Nanopore-Structured Nanocellulose Paper for Applications in Solar Thermal Heating

Recently, there has been remarkable progress in solar thermal heating by applying biomass-derived carbons, which can absorb and convert solar light into thermal energy. The design of subwavelength nanoporous and molecular structures of biomass-derived carbons is required for suppressed reflection and enhanced absorption of solar light. However, such designs are difficult because conventional biomass-derived carbons exhibit intrinsic microstructures and are prepared under specific carbonization conditions. In this study, a wood cellulose nanofiber-derived carbon is proposed to tailor both subwavelength nanoporous and molecular structures. Cellulose nanofibers are first constructed into a paper, denoted as nanopaper, exhibiting subwavelength nanoporous structures by tailoring the pore spaces between cellulose nanofibers. The as-prepared nanopaper is then carbonized at various controlled temperatures to tailor the cellulose molecular structure, i.e., grow graphitic carbon domains. The graphitic carbon domains grown by semicarbonization at 500 degrees C adequately balance solar absorption and reflection, while the subwavelength nanoporous structures suppress solar reflection. Thus, the semicarbonized nanopaper with tailored nanoporous and molecular structures exhibits superior solar thermal heating to competitive nanocarbons, also affording thermoelectric power generation. This study can guide the structural and functional design of bionanocarbons for solar thermal heating.

Automated summary

This study proposes a method for solar thermal heating using biomass-derived carbons and designs subwavelength nanoporous and molecular structures to enhance solar light absorption and suppress reflection. By constructing cellulose nanofibers into nanopaper and carbonizing it at controlled temperatures, the tailored nanoporous and molecular structures are achieved. The results show that the semicarbonized nanopaper with tailored structures exhibits superior performance in solar thermal heating.