Most evaporators that use solar heating rely on lenses or mirrors to concentrate sunlight, which makes it difficult to stop heat being lost to the environment and reduces efficiency. Liangbing Hu and his colleagues at the University of Maryland in College Park built a device using a 3D-printed material made of carbon nanotubes and graphene oxide, which absorbs 97% of incoming sunlight and rapidly warms up. This layer sits on a box with no bottom, which was 3D-printed using porous graphene oxide and nanostructured cellulose. When placed in shallow water, the walls of the box wick water to the top layer, where it is heated and escapes as steam.
The device used 85.6% of the absorbed energy to generate steam, which is one of the highest efficiencies achieved by evaporators. The approach could help to ease shortages in areas where water has to be sterilized or desalinated, the authors say.