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The construction of a phase junction photocatalyst can significantly enhance the photocatalytic performance with high selectivity for CO2 reduction. In this study, an S-scheme junction Cd0.5Zn0.5S/CoWO4 semiconductor with the coupling of a twin crystal Cd0.5Zn0.5S homojunction and CoWO4 was designed through a hydrothermal method, which could convert CO2 to CO with high efficiency under visible-light illumination. Cd0.5Zn0.5S-10%CoWO4 exhibited the optimal performance and its CO yield and selectivity were up to 318.68 μmol·g-1 and 95.90%, respectively, which were 4.54 and 1.62 times higher than that of twin crystal Cd0.5Zn0.5S. Moreover, the Cd0.5Zn0.5S homojunction with a zinc-blende and wurtzite phase and the S-scheme phase junction of Cd0.5Zn0.5S/CoWO4 enhanced the property of CO2 adsorption and accelerated the detachment of photogenerated carriers. The combination of photogenerated holes in Cd0.5Zn0.5S and the electrons of CoWO4 can retain the reduction sites to improve photocatalytic performance. This study provides a neoteric concept and reference for the construction of the S-scheme phase junction.

Using ion doping to engineer sulfur vacancies over metal sulfides is an effective method to improve photocatalytic properties, such vacancies form the center of the electron-captured state to promote the separation and transfer of photogenerated carriers. In this research, Yb/Er co-doped bulk Cd0.5Zn0.5S (CZS) was fabricated by a one-step simple hydrothermal process, and used for evaluating the catalytic activity for aquatic hydrogen production under visible light irradiation. The results showed that the Cd0.5Zn0.5S:Yb(15%), Er obtained exhibited a higher efficient photocatalytic activity of hydrogen evolution, in which the efficiency of Cd0.5Zn0.5S:Yb(15%), Er (422.0 μmol g−1 h−1) was 2.7 times higher than that of bare Cd0.5Zn0.5S (154.7 μmol g−1 h−1). This can be attributed to the augmented active surface area, the broadened spectral absorption of visible light and the facilitation of the separated efficiency of the photogenerated carriers. This finding provides a simple way to activate the metal-chalcogenides with S-vacancies for optimizing the photocatalytic performance.

Constructing organic-inorganic semiconductor heterojunctions is an efficient way to inhibit the recombination of photogenerated charge carriers and enhance photocatalytic performance of semiconductor. Herein, a novel heterojunction antimony sulfide-perylene diimides (Sb2S3-PDI) heterojunction has been fabricated through a facile hydrothermal method. Compared with bare Sb2S3 and PDI, the Sb2S3-PDI hybrid has showed significantly superior activity in photocatalytic reduction of Cr (VI). The superior photocatalytic performance of Sb2S3-PDI hybrid is due to the formation of type-I heterojunction, which leads to a more efficient separation and migration of photogenerated electron-hole pairs. This work is expected to promote continued interest in the construction of organic-inorganic semiconductor composites with enhanced photocatalytic performance.