Construction of manganese ferrite/zinc ferrite anchored graphene-based hierarchical aerogel photocatalysts following Z-scheme electron transfer for visible-light-driven carbon dioxide reduction.

Herein, atomic-level interfacial coupling between spinel-type MnFe2O4 (MFA) and ZnFe2O4 (ZFA) was achieved via a sol-gel method combined with phase separation. These composites were then anchored onto a three-dimensional graphene aerogel (GA) through ethylenediamine-assisted hydrothermal self-assembly, forming a hierarchically porous MFA/ZFA@GA with a high surface area (191.06 m2/g). The optimized MFA/ZFA@GA exhibited a CO production rate of 21.14 μmol·g-1·h-1 (96 % selectivity, 94 % stability) under visible light, a 3.87-fold enhancement over single-component systems. The in-situ MFA/ZFA heterojunction and graphene-enhanced electron transfer synergistically prolonged photogenerated electron lifetime by 10 times. The hierarchical pores also boosted CO2 adsorption (7.66 wt%), the appreciable saturation magnetization intensity (37.49 emu/g) enabled magnetic separation recovery, and *COOH monitoring confirmed rapid desorption kinetics for high CO selectivity. Experiments combined with theoretical calculations revealed a Z-scheme mechanism: MnFe2O4's reductive electrons (-0.79 V vs. NHE) drove CO2 reduction, while ZnFe2O4's oxidative holes (1.50 V vs. NHE) facilitated H2O oxidation. Strategic integration of heterostructures, carbon hybridization, and aerogel architectures offered an efficient pathway for monolithic photocatalyst design.