Ultraviolet and visible light active photothermal copper bismuth oxide nanostructures for solar steam generation

Abstract

The CuBi2O4 (CBO) microspheres comprising 1D nanostructures crystallized in a tetragonal crystal system with P4/ncc space group. The Cu and Bi ions in the CBO photothermal harvesters remained in stoichiometric 2+ and 3+ oxidation states, respectively. The CBO showed excellent absorption in the entire ultra-violet (UV) and visible spectrum, covering the prominent solar spectrum. The CBO microsphere formed by assembling 1D CBO nanorods possessed a specific surface area of 1.45 m2/g, and the temperature-dependent contact angle of water over CBO surface decreases upon increasing temperature, making it an excellent choice in solar steam generation (SSG) process. Thus, the presence of CBO-loaded cellulose paper at the air-water interface has demonstrated three times accelerated evaporation rate of 1.7 kg/m2h. Notably, the CBO-loaded cellulose paper delivered high stability with no change in evaporation rate even after consecutive cycles. The CBO exposed to the natural sunlight in the customized desalination setup provided >50 % CR/ER ratio for the salinity of 3.5, 10, and 20 wt % salty waters. Our findings establish that CBO is a highly desirable photo-material for SSG and has the potential to act as a solar light harvester for photovoltaic systems.