Dual-functional CuO/CN for highly efficient solar evaporation and water purification

Abstract Sunlight-clean water production from industrial wastewater, domestic sewage, and seawater is a sustainable water purification technology with the potential to solve environmental and energy problems. Semiconductor has good application prospects for photothermal conversion due to its advantages of earth-abundance, nontoxicity, and stability. While, most of its energy is released in the form of radiative relaxation, which leads to a low light-to-heat conversion efficiency. Enhancing its non-radiative relaxation is an effective way to improve light-to-heat conversion efficiency. In this work, heterostructured copper oxide/carbon nitride (CuO/CN) was designed to enhance non-radiative relaxation and thus improve the solar energy-to-thermal energy performance by constructing heterogeneous electric field. Electron paramagnetic resonance spectroscopy, X-ray photoelectron spectroscopy and differential charge density analyses proved the formation of heterogeneous electric fields between CuO and CN. Under the enhanced non-radiative relaxation, CuO/CN has an excellent light absorption range and carrier separation efficiency. The water evaporation rate under sunlight increased from 0.31 to 1.14 kg·m−2·h−1 and photothermal conversion efficiency increased from 19% to 72%. Simultaneously, CuO/CN can remove nearly 100% of the ions in seawater and Chemical Oxygen Demand (COD), Ammonia Nitrogen (NH3-N), Nitrate Nitrogen (NO3-N), and Total Phosphorus (TP) in industrial wastewater to produce clean water. Combined with photo-Fenton-like technology, it can effectively remove organic pollutants and volatile organic compounds (VOCs) from water. This work provides an efficient solar-clean water production technology with excellent pollution decontamination ability, which will be extremely attractive for future life.