Directed charge transfer of Zn-O bridge of atomistic tandem dual Z-scheme heterojunction for photocatalytic CO2 reduction

Abstract

Photocatalytic CO₂ reduction (PCR) is limited by unsatisfied activity and selectivity. The integration of molecular photocatalysts with semiconductors can solve the above two issues simultaneously. However, most of the organic-inorganic heterojunctions are bulky-based morphologies, which are still restricted by the control of surface areas and charge transfer. Herein, a tandem dual Z-scheme heterostructure was synthesized by assembling cobalt porphyrin ([meso-tetra (4-sulfonate phenyl) porphyrinato], CoTPPS) on hollow-structured TiO₂@ZnIn₂S₄ (H-TiO₂@ZIS). The optimized H-TiO₂@ZIS@CoTPPS exhibits superior solar fuel evolution of 158.15 μmol_CO g⁻¹·h⁻¹ via the PCR process, which is superior to most reported TiO₂ and ZIS-based photocatalysts. The exceptional photocatalytic performance is ascribed to enhanced light absorption, elevated surface areas, directed charge separation, and improved CO₂ activation. Specifically, the double built-in electric field (IEF) and the Zn-O bond of dual Z-scheme structures facilitate fast charge separation. Detailed charge transfer dynamics of H-TiO₂@ZIS@CoTPPS are investigated by experimental characterizations and density functional theory (DFT) calculations. This investigation provides atomistic insight into unique dual Z-scheme heterostructure and offers a new paradigm for solar-driven energy conversion