Geometric light-trapping architecture in peony-like 3D graphene hydrogel for efficient solar steam generation

Hydrogel-based solar interfacial evaporation for seawater desalination is limited by inadequate evaporation rates and inefficient light harvesting, particularly under non-perpendicular illumination. Herein, This study introduces a peony-like single-layer graphene oxide (SLGO)/polyvinyl alcohol (PVA) 3D hydrogel evaporator (GPH) featuring a geometric light-trapping architecture. By exploiting synergistic edge curvature gradients and surface aperiodic wrinkles, the GPH induces multiple internal reflections to effectively manipulate the optical path, thereby overcoming the light absorption limitations of conventional evaporators under oblique incidence. Beyond optical management, precisely tuning the SLGO/PVA ratio optimizes the polymer network's hydrogen bonding, which elevates the intermediate/free water ratio to 0.78 and drastically reduces the water evaporation enthalpy to 1248 J g −1 (cf. 2450 J g −1 for bulk water). Consequently, an exceptional evaporation rate of 2.761 kg m −2  h −1 (20% enhancement over conventional homogeneous hydrogels) and energy efficiency of 91.61% are achieved under 1-sun intensity. Crucially, the hierarchical 3D porous architecture facilitates rapid water replenishment and efficient ion diffusion, endowing the evaporator with robust salt-rejection capabilities. Moreover, the GPH demonstrates outstanding mechanical robustness, with a high fracture strain of 800% in uniaxial tensile tests, indicating its resilience and potential for practical application. This work presents a promising pathway for efficient, reliable seawater desalination and offers a novel perspective for next-generation interfacial solar evaporation technologies.