Enhanced solar-to-steam conversion efficiency using CuO-polyaniline yolk-shell structures

Herein, the low-cost copper oxide was encapsulated in the polyaniline (PANI) structure forming a yolk-shell (YS) platform which can provide a large surface area and sufficient active sites and enhance light scattering in its hollow space or voids, both of which can significantly improve the near-full usage of solar energy. The fabrication of the YS structure was assisted with a soft template (hexadecyltrimethylammonium bromide, CTAB) which the removed by the acidic etching process producing uniform voids through the composite structure. Moreover, the etching process using an acidic medium resulted in the formation of the PANI emeraldine salt which is beneficial for the salt-resistant properties of the composite. The encapsulated CuO@void@Es-PANI showed an outstanding rate of water evaporation of 1.91 kg m⁻² h⁻¹ and a corresponding high Solar-to-Steam conversion efficiency of 98.9 % under the irradiation of 1 sun compared to that of the normal mixed CuO/PANI (1.53 kg m⁻² h⁻¹ and 81.3 %). Meanwhile, the same high evaporation flux was approximately obtained after a continuous 72 h even in high saline water or contaminated seawater.