Triggered Photoexcited Electrons Transfer and Spin Polarization through 3dx2–y2–2pz Orbital Hybridization for Synergistic Solar-Thermal/Photocatalytic Water Purification

Although solar steam generation has been combined with photocatalytic degradation for purifying wastewater, the inherent synergistic effects on enhancing solar-thermal water evaporation and photodegradation are poorly understood. Herein, synergistic solar-thermal and photocatalytic purification of wastewater triggered by photoexcited electron transfer and spin polarization is realized by designing a flow-bed water purification system with a bacterial cellulose/α-Fe₂O₃ nanodisk/carbon nanotube (BFC) composite film for the continuous solar-thermal evaporation of water and simultaneous photocatalytic degradation of organic pollutants. The photogenerated electrons in the 3dx²-y² orbitals of the Fe atoms of α-Fe₂O₃ can transfer to the 2p_z orbitals of the C atoms of carbon nanotubes, induced by the work function differences. The separation of photogenerated carriers is enhanced by the built-in electric field and the spin polarization effect, generating more active redox species to improve the photocatalytic degradation performance. Moreover, the photoexcited electrons injected into the carbon nanotubes can participate in solar-thermal conversion via a relaxation process to generate more heat, promoting solar steam generation performance. A flow-bed water purification system is established on the basis of the synergistic solar-thermal/photocatalytic effects for efficiently purifying various wastewater. The purified water is eligible for direct irrigation of crops without any obvious inhibition phenomena.