Narrow-Bandgap LaMO3 (M = Ni, Co) nanomaterials for efficient interfacial solar steam generation

Photothermal water evaporation provides a pathway towards a promising solution to global freshwater scarcity. Synergistic integration of functions in a material in diverse directions is a key strategy for designing multifunctional materials. Lanthanum-based perovskite complex oxides LaMO3 (M = Ni and Co) have narrow band gaps with a high absorption coefficient. These functionalities have not been appropriately explored for photothermal energy conversion. Here, we synthesized nanostructured metallic LaNiO3 and semiconducting LaCoO3 and used them to design interfacial solar steam generators. Effective light absorption capability over the entire solar spectrum of these materials leads to a photothermal efficiency of the order of 83% for both materials. Using a cone-shaped 3D interfacial steam generator with a LaNiO3 absorber, we achieved an evaporation rate of 2.3 kg m-2 h-1, corresponding to solar vapor generation efficiency of over 95%. To the best of our knowledge, this evaporation rate is higher than any oxide-based interfacial solar steam generator reported so far. Furthermore, we have also shown an effective way of using such evaporators for long-term seawater desalination.