Solar　steam　generation　is　a　promising　technology　to　solve　the　freshwater　crisis.　With　the　continuous　research　of　this　technology,　apart　from　developing　efficient　photothermal　conversion　materials　that　can　increase　the　evaporation　rate,　it　is　found　that　a　reasonable　structural　design　can　also　achieve　this　goal.　In　this　study,　we　fabricated　a　bilayer　structural　carbon-based　hydrogel　composite　material.　The　composite　material　achieved　a　maximum　evaporation　rate　of　2.19　kg　m−2　h−1　and　an　energy　conversion　efficiency　of　93.7%　under　one　sun　(1　kW　m−2)　irradiation,　which　is　superior　to　most　evaporators.　Moreover,　the　fabricated　composite　material　exhibited　outstanding　seawater　desalination　performance　and　durability,　expanding　the　range　of　its　practical　applicability.　In　addition,　the　scalability　and　portability　allow　the　composite　to　easily　withstand　various　complex　environments,　and　its　production　cost　is　low,　making　it　easily　implemented　on　a　large　scale　in　economically　backward　areas.　This　study　provides　valuable　information　for　designing　and　producing　composite-structure　hydrogel　evaporators.[Figure　not　available:　see　fulltext.].　©　2023,　Science　China　Press.