NiMn-LDH/polypyrrole photothermal structures for interfacial solar steam generation

Interfacial solar steam generation (ISSG) is severely limited by excessive salt accumulation and inefficient water movement. To overcome this, a hydratable skeleton is engineered through in-situ polymerization of polypyrrole (PPy) onto a NiMn-layered double hydroxide (LDH) for balanced water transport and effective salt-resistance without deterring the evaporation flux. The oxidation of Mn 2+  → Mn 3+ in the LDH matrix and shielding of PPy polymeric network (NiMn-LDH/PPy) endows stable, rapid hydration pathways for confined ion channels for salt rejection. The evaporator exhibits broadband light absorption (∼89 %), and achieves a high evaporation flux of 1.90 kg m −2  h −1 using seawater (3.5 wt%) under 1 kW m −2 solar intensity, maintained even after 20 cycles with greater flux retention. The hydratable skeleton's unique structure enables localized heat management (36.6 °C) and in-situ salt-ion dissociation (1.5 g NaCl completely rejected in 2 h), preventing crystallization. The structural optimization for effective heat mass transfer validates its structural stability under different humidity and environmental temperatures. The evaporation performance has been examined under natural conditions during different weather conditions, i.e., winter (1.76 kg m −2  h −1 ), and summer (1.82 kg m −2  h −1 ), in the same geographical location. This work provides a robust, process-engineered solution for durable solar desalination.