Full-spectrum-responsive Ti4O7-PVA nanocomposite hydrogel with ultrahigh evaporation rate for efficient solar steam generation

Abstract

Solar steam generation (SSG) via interfacial photothermal conversion has emerged in sustainable seawater desalination and sewage purification. One of the grand challenges is that low light absorption generally limits photothermal materials on water evaporation rates and insufficient on-board performance for real practice. Herein, we propose a “molecular/phase dual-locking” strategy to homogeneously composite Magnéli phases like Ti4O7 nanoparticles and poly(vinyl alcohol) (PVA) by chemical-physical bi-crosslinking. As-obtained Ti4O7-PVA nanocomposite hydrogels (TPNHs) exhibit a narrow bandgap (~0.81 eV) for highly efficient sunlight absorption all through UV–vis–NIR full-spectrum wavelengths (up to ~99.56 %) and enable a record high evaporation rate of ∼4.45 kg m−2 h−1 with outstanding energy efficiency (~90.69 %) under one sun irradiation. A 20−day continuous test in real seawater manifests excellent long-term performance stability of TPNHs without salt accumulation. We further demonstrate the SSG efficacy of such hydrogels by applying them for efficient desalination/purification of varying seawater and sewage samples with low-to-high salinity, strong acids/bases, heavy metal ions, and organic dyes. This “molecular/phase dual-locking” design strategy and resultant Ti4O7-PVA nanocomposite hydrogels present a promising methodology to boost practical applications for seawater desalination and sewage purification.