One-pot solvothermal synthesis of flower-like Fe-doped InS/FeS S-scheme hetero-microspheres with enhanced interfacial electric field and boosted visible-light-driven CO reduction.

S-scheme heterojunctions hold great potential for CO photoreduction into solar fuels, but their activities are severely limited by the low efficiency of interfacial charge transfer. In this work, a facile one-pot solvothermal reaction has been developed to dope Fe into flower-like InS/FeS hetero-microspheres (Fe-InS/FeS HMSs), which are demonstrated as an efficient S-scheme photocatalyst for visible-light-driven CO photoreduction. The doping of Fe not only reduces the bandgap of InS and thus extends the optical response to the visible-light region, but also increases the densities of donors and sulfur vacancies, which leads to an elevated Fermi level (E). The difference of E between InS and FeS is enlarged and their band bending at the interface is therefore enhanced, which results in promoted carriers transfer in the S-scheme pathway due to the reinforced interfacial electric field. Moreover, Fe-doped InS reduces the formation energy of the *CO intermediate, which thermodynamically favors the CO evolution at the surface. As a result, the Fe-InS/FeS HMSs exhibit a significantly boosted CO photoreduction activity in comparison with bare InS and Fe-InS samples. This work demonstrates the great potential of heteroatom-engineered S-scheme photocatalysts for CO photoreduction.