Abstract: The introduction of metal single atoms (SAs) and nanoparticles (NPs) are effective approaches to modify electronic configuration of semiconductors, whereas recognizing the synergistic effects of metal SAs and NPs are still challenging in photocatalytic water purification. Herein, a general strategy is achieved by subsequentially anchoring Fe SAs and Fe NPs in graphitic carbon nitride. The modification of Fe SAs and Fe NPs improves the energy band structure and constructs a gradient charge polarization, directly expanding the optical absorption range and facilitating the efficient separation and transfer of charge carriers. With the assistance of the gradient charge polarization, pollutants are readily oxidated by h⁺, which strengthens the continuous reduction of O₂ on Fe NPs for pollutant oxidation in water. This work reinforces the synergistic effect of SAs and NPs on electronic configuration modulation at the atomic level, which exhibits great potential for the construction of an efficient and sustainable water purification system.

Key words: Single atoms, Nanoparticles, Synergistic effects, Photocatalysis, Electronic configuration modulation