Confined Immobilization of Plasmonic Cu ₃ P into Self-Assembled Carbon Fibers Reinforced Directional Hot Electron Transfer for Solar Seawater Desalination

Solar-driven seawater evaporation requires efficient photothermal absorbers, in which the photo-to-thermal conversion efficiency largely depends on the nonradiative relaxation of photoexcited electrons in the form of heat but faces challenges in manipulation. Herein, we report a self-assembled carbon fiber that serves as a support to confine Cu3P clusters (PNCNF/Cu3P), which functions as a floatable absorber for photothermal seawater desalination. Cavities in the carbon assembly chelate Cu2+ ions and confine the growth of Cu3P clusters during phosphidation. Spectroscopic analysis demonstrates an interfacial electron distribution between Cu3P and PNCNF, which is driven by the electron-withdrawing capacity of N and P-codoped graphitic carbon domains, leading to a directional hot electron transfer from the plasmonic Cu3P to PNCNF along the Cu–P–C pathway under illumination. Density functional theory (DFT) calculations demonstrate that charge densities move from Cu3P to carbon when an electron is excited from the valence band (VB) to the conduction band (CB) state. This PNCNF/Cu3P absorber shows outstanding activity for solar seawater evaporation, achieving an evaporation rate of 2.6 kg m–2 h–1 with a solar-to-vapor efficiency of 96%. COMSOL simulations further verify that the rationally designed heterostructure significantly enhances water transport and thermal localization and predict its potential for large-scale freshwater production.