Diluted CO₂ photoreduction and charge transfer dynamics investigation in biomimetic S-scheme heterojunction

The strategic design of novel photocatalysts for diluted CO₂ conversion is imperative, yet their catalytic activity is often constrained by sluggish charge transfer kinetics. A biomimetic heterojunction photocatalyst was fabricated via in-situ deposition of SnS₂ nanosheets onto resorcinol-formaldehyde (RF) resin spheres, tailored for the photoreduction of diluted CO₂ under simulated solar conditions. Serving as a growth substrate, RF spheres enable the formation of SnS₂, yielding core-shell biomimetic photocatalysts with intimate interfacial contact. They synergistically enhance SnS₂'s visible-light absorption while establishing an step-scheme (S-scheme) heterojunction, a synergistic effect that enables efficient charge separation and transfer. The CO production rate of the optimized SnS₂@RF sample attained 77.3 μmol g^-1 h^-1, surpassing SnS₂ nanosheets and RF spheres by 3.2 and 2.2 times, respectively. The distinct charge transfer in the S-scheme is facilitated by mechanistic investigations using femtosecond transient absorption spectroscopy (fs-TAS) and in situ X-ray photoelectron spectroscopy (XPS). This work demonstrates an effective strategy for enhancing biomimetic photocatalysts via the construction of S-scheme heterojunctions and provides atomistic insights into their solar fuel generation mechanisms.