Direct Z-scheme CeO2@LDH core–shell heterostructure for photodegradation of Rhodamine B by synergistic persulfate activation

Highlights: • A novel core–shell direct Z-scheme CeO₂@LDH heterostructure photocatalyst is prepared. • It is the first reported that Z-scheme heterojunction photocatalysts activate PS system. • The CeO₂@LDH+PS system exhibits excellent efficiency, great stability and certain universality. • The built-in electric field improves the separation efficiency and transfer rate of carriers. • The direct Z-scheme mechanism is confirmed by DFT calculation. Photocatalytic activation of persulfate (PAPS) is considered an efficient and green approach for the mitigation of organic pollutants because of its advantages in low energy consumption and high reusability of photocatalysts. Herein, direct Z-scheme CeO₂@LDH heterojunction photocatalyst with a core–shell structure is constructed. We reveal that CeO₂@LDH exhibits excellent persulfate (PS) activation performance and high degradation efficiency of RhB under visible light irradiation. Control experiments by quenching catalytically active radicals and analysis of electron paramagnetic resonance (ESR) spectra suggest that the sulfate radical (SO₄·⁻) generated by photocatalytic activation of PS, together with superoxide radical (·O₂⁻) and hydroxyl radical (·OH), degrade pollutants synergistically. Density functional theory (DFT) calculations indicate that the built-in electric field across the surface of CeO₂ and LDH is the intrinsic driving force for the efficient transfer of hot carriers in the Z-scheme heterojunction. The construction of this transfer path can effectively engineer the interfacial band structure and inhibit the recombination of photogenerated electron-hole pairs and promote their transportation. Meanwhile, electrons were found to accumulate at the conduction band (CB) of LDHs and holes populate at valence band (VB) of CeO₂, generating more active species for photodegradation of RhB. We demonstrate that the Z-scheme heterojunction photocatalyst activated PS system (Z-scheme/PS) is a promising method to degrade RhB and potentially organic pollutants in general.