A novel hierarchical chromium black membrane prepared by electroplating for desalination

Abstract

Solar-driven interfacial evaporation (SDIE), a technology for local solar energy conversion through photothermal materials, has been greatly developed. The metal oxide semiconductors have excellent photothermal conversion performance and are considered the most promising materials for photothermal conversion. Hierarchical structure with large surface area is beneficial to improve the photothermal conversion efficiency through the light-trapping effect and reduces the evaporation enthalpy of water. Herein, chromium black (Cr, Cr2O3, CrO3-x) photothermal membranes (CBPM) with ganoderma-like hierarchical structure were prepared by electrochemical oxidation. Due to the small interlayer spacing of the ganoderma-like structure, the light absorption of CBPM (M7) can reach 78.53 %, which in turn promotes the conversion of solar energy due to the low thermal conductivity of the chromium black layer, resulting in a high evaporation rate of 1.64 kg m−2 h−1. The solar-to-vapor conversion efficiency is up to 90.39 % under 1 sun irradiation. Meanwhile, the superhydrophilicity of the membrane is conducive to salt redissolution at night, so there was not much performance degradation after 24 cycles. This study provides a new solution for water treatment using chromium black as a photothermal material with great potential for solar production of fresh water.