Facile Deflagration Synthesis of Hollow Carbon Nanospheres with Efficient Performance for Solar Water Evaporation

Solar water evaporation is a promising and environment-friendly approach to relieve global water scarcity issues. Currently, many reports show that the voids and porous structure are beneficial to the absorption of solar energy to generate water steam. Herein, carbon nanospheres with central cavity structures are rationally designed by the one-step NaN₃/fluorinated graphite deflagration method. The Na clusters derived from NaN₃ deflagration are not only provided as the hollow templates but also react with fluorinated graphite to release heat, further boosting the formation of hollow carbon nanospheres (HCSs). Benefiting from the diversity of carbon nanomaterials, rough surface, unique hollow structures, and numerous micron/submicron holes, the light absorption ability, heat localization, and water supply capacity of HCSs have been significantly enhanced. Because of these advantages, the HCS-3 exhibits an excellent water evaporation efficiency of 92.7% at 1 kW m^-2, which is much higher than that of carbon nanospheres, graphene oxide, and even most of the previous carbon materials. In addition, we demonstrated that the HCSs have a long-term stability and high efficiency of production of drinkable water and purifying various types of wastewater, including seawater, strong acid/alkaline water, and water containing dyes. To sum up, the deflagration synthetic technology as a facile and ultrafast process can be a new insight for future photothermal material design.