Poly(p-phenylenediamine)-Doped Reactive Nanofiber Membrane for Self-Enhanced Solar-Driven Interfacial Evaporation

An efficient solar evaporation system with a nanofiber membrane as carrier and poly(p-phenylenediamine) (PPPD) as a photothermal agent was fabricated, and an incredible self-enhancement effect was discovered during the water evaporation process. The PPPD nanoparticles are first synthesized in situ in the spinning solution, followed by the formation of photothermal nanofiber membranes (PTNFMs) with reactive amino-imine groups through electrospinning technology. Under one sun intensity, the membrane evaporator shows a photothermal conversion efficiency of 91.2% and achieves a water evaporation rate of 1.77 kg·m–2·h–1. During continuous operation, the photothermal performance of the PTNFM is progressively enhanced with the evaporation rate increasing up to 1.91 kg·m–2·h–1, indicating an apparent self-enhancement effect. Particularly, a photothermal differential scanning calorimeter (DSC) was introduced to precisely measure the photothermal conversion energy of the membranes, revealing that the PTNFM is improved by 1.3 times in photothermal conversion efficiency after six consecutive days of use. Contrary to those conventional membranes, which are prone to fouling and experience a decline in performance due to salt deposit in desalination processes, this system demonstrates a self-reinforcing performance. Furthermore, the research uncovers the enhancement mechanism of the present system in the photothermal process based on the interaction between salt ions and PPPD.