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Constructing heterostructures and designing excellent structures to simulate natural photosynthesis are effective ways to efficiently and selectively convert CO2into products with high energy. Herein, a novel 0D/3D heterostructure composed of Cd0.5Zn0.5S quantum dots and CdIn2S4nano-octahedron was resoundingly fabricated via a simple solvothermal–coprecipitation method. The optimal yields of CO2photoreduction to CO and CH4over the Cd0.5Zn0.5S/CdIn2S4composite material could reach up to 14.07 and 4.23 μmol/g/h, respectively, which was primarily due to the synergistic effect of the 0D/3D heterostructure and unique morphology, thus accelerating the transfer of light-induced carriers. In addition, the as-fabricated composite exhibited excellent stability and weaker photocorrosion. Hence, this work could provide a simple and efficient route for the design and construction of photocatalysts with superior activity for CO2photoreduction.

In this work, an urchinlike W18O49/g-C3N4composite was fabricated via a simple hydrothermal process. The photocatalytic CO2conversion reaction was applied to evaluate the photocatalytic behavior of this catalytic system, and the WOCN-20 wt % heterojunction displayed superior photocatalytic behavior under full spectrum light irradiation, which was 6.46 μmol·h–1·g–1for CO and 3.97 μmol·h–1·g–1for CH4, respectively. Furthermore, in the near-infrared region, the composite photocatalysts also displayed excellent photocatalytic performance. A large number of characterizations and testing measures were carried out to study the components, morphology, and physicochemical properties of W18O49/g-C3N4photocatalyst, which were helpful to exploring and understanding the reasons for the improvement of catalytic performance. The boosted activity resulted from the tight contact between W18O49and g-C3N4and the formation of a Z-scheme heterojunction. The local surface plasmonic resonance (LSPR) of W5+also contributed to the realization of efficient photocatalysis under near-infrared light. The Z-scheme electron transport model could realize the efficient separation of light-induced e––h+pairs and reduce the recombination rate, thereby boosting the CO2photocatalytic reduction process.

Metal oxide-based Z-scheme heterojunction photocatalyst can effectually separate electrons and holes, and simultaneously ensure that photocatalysts can maintain appropriate conduction band and valence band positions, thus maintaining a strong redox capacity. This paper introduced the mechanism and types of Z-scheme heterojunction photocatalysts. Nevertheless, direct Z-scheme photocatalytic mechanism was gradually replaced by new S-scheme heterojunction mechanism. Thus, this review also briefly discussed the improved Z-scheme mechanism, that is, S-scheme heterojunction, so that the mechanism of the charge transfer process could be understood more intuitively and clearly. Then we emphatically summarized the applications of different types of heterojunctions in the field of photocatalysis, ranging from environmental remediation to energy conversion. In addition, several typical traditional methods and new strategies for preparing Z-scheme heterojunctions were summed up. Finally, the breakthrough and development prospect of Z-scheme heterojunction were discussed.

The two-dimensional transition metal carbides, nitrides, and/or carbonitrides (MXenes) were first synthesized in 2011. In the last couple of years, MXenes have drawn intense interest in the field of catalysts, ion batteries, energy storage, and sensors due to the high chemical diversity and structural complexity of MXenes. In this review, the preparation method, structure, and electronic and optical properties of MXene are introduced in detail. More importantly, MXenes, as a cocatalyst, are widely applied to combine with various common photocatalysts such as metal oxide, metal sulfide, and g-C3N4to improve the performance of photocatalytic H2evolution, CO2conversion, photocatalytic degradation of pollutants, and nitrogen fixation. The large specific surface area, hydrophilicity, excellent electronic conductivity, and surface groups of MXenes play crucial roles in boosting the photocatalytic efficiency of the semiconductor catalysts. Lastly, challenges and invigorating outlooks of the photocatalytic applications of MXene materials are also discussed and concluded.