Optimizing coupling effect of confined FeNi nanoalloys within graphitic carbon nanofibers to improve photothermal energy conversion efficiency for solar water purification

Sustainable and energy-efficient water purification by harnessing solar energy is critical to tackling the challenges of water scarcity and the on-going water pollution crisis. Nevertheless, the biggest challenge to the practical deployment of solar-driven water purification, however, continues to be the poor solar evaporation efficiency of materials. Herein, FeNi nanoalloys encapsulated in graphitic carbon nanofibers (FeNi3/CNF) using Prussian blue analogue (PBAs) derivatives were fabricated using electrospinning and carbonization. The PBAs metal precursors play a critical role in encapsulating and safeguarding the FeNi alloy nanostructures from oxidation and agglomeration challenges. Furthermore, the synergistic effects between the non-noble hybrid plasmonic nanoalloys and graphitic CNFs can be constructed and optimized from the mass loading of PBAs precursor. Benefiting from the broad solar absorption band, high specific surface area, abundant micro-mesopores, and well-organized interlayer channel, the resultant 2D FeNi3/CNF solar evaporator demonstrates an efficient water evaporation rate of 1.51 kg m-2 h-1 with an outstanding solar evaporation efficiency of 93.3 % under one sun irradiation, among the best values reported thus far. Impressively, the resultant 2D FeNi3/CNF solar evaporator can be constructed using only 0.02 kg m-2 loading of photothermal materials without compromising evaporation performance, which highlights its cost-efficiency in the practical application. Furthermore, the desalinated water meets the drinking standards of the World Health Organization (WHO) with an efficient 99 % separation of multiple organic industrial dye pollutants. Hence, this work demonstrates an efficient cost-effective approach to novel non-noble plasmonic alloy-based metal-carbon composites for enhanced solar-driven interfacial evaporation and wastewater purification.