One-pot solvothermal synthesis of flower-like Fe-doped In2S3/Fe3S4 S-scheme hetero-microspheres with enhanced interfacial electric field and boosted visible-light-driven CO2 reduction

S-scheme heterojunctions hold great potential for CO2 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 In2S3/Fe3S4 hetero-microspheres (Fe-In2S3/Fe3S4 HMSs), which are demonstrated as an efficient S-scheme photocatalyst for visible-light-driven CO2 photoreduction. The doping of Fe not only reduces the bandgap of In2S3 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 (Ef). The difference of Ef between In2S3 and Fe3S4 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 In2S3 reduces the formation energy of the *CO intermediate, which thermodynamically favors the CO evolution at the surface. As a result, the Fe-In2S3/Fe3S4 HMSs exhibit a significantly boosted CO2 photoreduction activity in comparison with bare In2S3 and Fe-In2S3 samples. This work demonstrates the great potential of heteroatom-engineered S-scheme photocatalysts for CO2 photoreduction.

Combined Schottky junction and doping effect in CdxZn1-xS@Au/BiVO4 Z-Scheme photocatalyst with boosted carriers charge separation for CO2 reduction by H2O

A Z-scheme photosystems combining Schottky junction and loading of applicable bandgap semiconductor is beneficial for enhancing the charge carriers' separation/transfer as well as maintain their excellent redox ability. Here, Cd_xZn_1-xS@Au was in-situ deposited on the (010) facets of BiVO₄ taking Au as a bridge for constructing a sandwich structure Cd_xZn_1-xS@Au/BiVO₄ Z-scheme photocatalyst. The electrons in BiVO₄ (010) migrate unidirectionally to Au nanoparticles across the Schottky junction and effectively suppress opposite electrons flow, then be captured by the excited holes in Cd_xZn_1-xS. Furthermore, Zn-doping also contributes to an appropriate redox ability and charge carriers separation. Benefiting from the dual-facilitated effects, the ternary Cd_xZn_1-xS@Au/BiVO₄ exhibited superior photocatalytic activity for CO₂ reduction under visible light irradiation using H₂O as a reducing agent, as compared with CdS and CdS@Au/BiVO₄. Furthermore, the intermediate product HCOO* fixed on the surface of Cd_xZn_1-xS@Au/BiVO₄ is identified by in-situ FT-IR, playing a key role in the conversion of CO₂ to CO and then improve photocatalytic selectivity.

Functional facet isotype junction and semiconductor/r-GO minor Schottky barrier tailored In2S3@r-GO@(040/110)-BiVO4 ternary hybrid

Efficient interfacial exciton transfer and separation have been regarded as the foremost confront of semiconductor oriented photocatalysis. The simultaneous discovery of crystal facet isotype heterojunction across the (040)-reduction and (110)-oxidation facet of monoclinic scheelite BiVO₄ crystal; and Schottky junction at the interfacial region of BiVO₄ crystal with well-exposed functional (040) facet and r-GO sheets has been reflected as an efficient electron injection route. In this context lucrative architecture of a high productive all-solid-state Z-scheme charge transfer dynamics In₂S₃@r-GO@(040/110)-BiVO₄ isotype ternary hybrid photocatalyst was carried out and well-validated by FESEM and HRTEM analyses. Photoelectrochemical measurements have revealed that the accumulated photo-electrons over the exposed (040)-crystal facet of BiVO₄ truncated bipyramid easily cross the minor Schottky junction to expedite the unidirectional injection to the π-π conjugated two-dimensional planar r-GO structure. Besides, subsequent trapping of the injected electrons by the photoinduced holes of In₂S₃ leading to a superior charge carrier separation in the material, validated by PL, EIS, Mott-Schottky, and transient photocurrent analysis. Perceptibly, this intimate interfacial interacted crystal facet dependent electron shuttle provided a longer life span electrons and holes to settle in the conduction band of In₂S₃ and valence band of (110)-BiVO₄, respectively, for elevated photo-activity efficiency. The In₂S₃@r-GO@(040/110)-BiVO₄ ternary hybrid contributes 89.7% of Ciprofloxacin (CIP) detoxification in 150 min and 885.43 µmol of O₂ evolution in 120 min. More in, the constructive interrelations of resultant Physico-chemical, photoelectrochemical, and augmented photocatalytic redox efficiency were well-illustrated. This unique association semiconductor ternary hybrid photocatalyst via metal-free mediating agent crystal-facet sandwich structure will provide a scientific innovative basis for rational design and realization of advanced Z-scheme photocatalytic system for energy and environment application.