Coupled photothermal and joule-heating process for stable and efficient interfacial evaporation

Access to water and clean energy is a major concern in modern society. Although there have been huge improvements in the efficiency of solar interfacial evaporation as a technique to obtain clean water, it remains challenging for solar-driven interfacial evaporation systems to maintain stable steam generation and water production without an energy storage system. To overcome these issues, we propose a coupled tunable photothermal and joule-heating process for interfacial evaporation using a low-cost commercial carbon fiber (CF) material. The CF material had a high porosity, good water absorption, salt-rejection ability, and high total absorption (93%) and electrical conductivity (1666 S/m), which make it suitable for photothermal and joule-heating conversion. By coupling photothermal and joule-heating processes through the same CF material as the evaporation medium, a stable and efficient interfacial evaporation performance could be achieved, in which the input power of the electrical energy could be adjusted to match the loss of solar energy. Through coupled evaporation experiments, it was found that the evaporation rate reached 1.36 kg m−2 h−1, with sun irradiation power of 1 kW m−2. For photothermal conversion or joule-heating conversion, the efficiency first decreased and then increased. "Cold Vapor'', with a lower input power, resulted in a higher efficiency, whereas heat localization led to a significant decrease in the relative ratio of the thermal losses and improved the efficiency at a higher input power. This work has further improved the multi-process coupling and multi-energy complementary process and will promote its actual application.