Z-scheme SnFe2O4-graphitic carbon nitride: Reusable, magnetic catalysts for enhanced photocatalytic CO2 reduction

The challenge in developing suitable photocatalysts for converting CO2 to solar fuels is to achieve effective CO2 adsorption capacity and high charge separation efficiency. In this report, we demonstrate the construction of a Z-scheme photocatalyst composed of coupling graphitic carbon nitride (g-C3N4) and SnFe2O4 semiconductors (denoted as SFO-CN) based on theoretical calculations and the characterization of their performance in photocatalytic CO2 reduction. The Z-scheme SFO-CN composite shows an enhanced photocatalytic activity in the reduction of CO2 to CO, yielding a CO evolution rate of 7.56 mu mol/g/h without any cocatalyst and sacrifice reagent, which is 2.2 times higher than that of CN alone (3.45 mu mol/g/h). Additionally, the SFO-CN catalyst can be easily separated from its aqueous dispersions for recycled usage due to its room temperature ferromagnetism. Characterizations revealed that the enhanced photocatalytic reduction activity of SFO-CN can be ascribed to the following unique characteristics: (1) SFO promotes the CO2 adsorption on the catalyst surface; (2) the Z-scheme charge transfer efficiently enhances the separation of the electron-hole pairs and maintains the high reducibility of electrons in the SFO conduction band. This study creates new opportunities for SFO and other ferrimagnetic spinel-type complex oxides-based Z-scheme system for solar fuel generation.