Fabrication of Co3O4@ZnIn2S4 for photocatalytic hydrogen evolution: Insights into the synergistic mechanism of photothermal effect and heterojunction

Construction of two-dimensional zinc indium sulfide/bismuth titanate nanoplate with S-scheme heterojunction for enhanced photocatalytic hydrogen evolution

Improving the separation efficiency of photogenerated carriers plays an important role in photocatalysis. In this study, two-dimensional (2D)/2D zinc indium sulfide (ZnIn2S4)/bismuth titanate (Bi4Ti3O12) nanoplate heterojunctions were synthesized to alter the Bi4Ti3O12 morphology, modulate the bandgap of Bi4Ti3O12, and enhance the utilization of light. Meanwhile, the construction of the S-scheme heterojunction establishes an internal electric field at the ZnIn2S4/Bi4Ti3O12 heterojunctions interface and achieves the spatial separation of photogenerated charges. The hydrogen production rate of ZnIn2S4/Bi4Ti3O12 nanoplate with the optimal ratio reaches 27.50 mmol h-1 g-1, which is 1.5 times higher than that of ZnIn2S4/Bi4Ti3O12 nanoflower (18.28 mmol h-1 g-1) and 2.4 times higher than that of ZnIn2S4 (11.69 mmol h-1 g-1). The apparent quantum efficiency of ZnIn2S4/Bi4Ti3O12 nanoplate reached 57.9 % under a single wavelength of light at 370 nm. This work provides insights into the study of new materials for photocatalytic hydrogen production.

In situ Mo-doped ZnIn2S4/Ni-Ni Hofmann-type coordination polymer composites for photocatalytic hydrogen evolution reaction

Solar energy-assisted hydrogen production technology is an essential tool for exploring hydrogen energy. To date, semiconductors have been used as the primary photocatalyst to generate hydrogen via photocatalytic water splitting. However, the high photogenerated electron-hole recombination rate of semiconductor photocatalysts results in a low hydrogen production rate. Herein, the synergistic effect of Mo-ion doping and the incorporation of Ni-based Hofmann-type coordination polymer (Ni-Ni HCP) on the photocatalytic performance of ZnIn2S4 (ZIS) is investigated. The hydrogen production rate of the prepared in-situ Mo doped ZnIn2S4 wrapped Ni-Ni HCP (Ni-Ni HCP/Mo-ZIS) sample under visible-light irradiation is 26.7 mmol g-1h-1, which is 10 times that of pure ZIS. Hydrogen production rate test, microscopic characterization, and density functional theory calculation confirm that the proposed dual modulation approach (combined ion doping and heterogeneous structure construction) could effectively increase the photocatalytic efficiency of ZIS. The stability of prepared samples is also examined by four-cycle photocatalytic hydrogen production tests. The proposed integrated method opens a new route for advancing renewable energy technology towards a sustainable future.

Synthesize magnetic ZnFe2O4@C/Cd0.9Zn0.1S catalysts with S-scheme heterojunction to achieve extraordinary hydrogen production efficiency

Suppressing the electron-hole recombination rate of catalyst legitimately is one of the effective strategies to improve photocatalytic hydrogen evolution. Herein, carbon-coated metal oxide, ZnFe2O4@C (ZFO@C), nanoparticles were synthesized and employed to couple with quadrupedal Cd0.9Zn0.1S (CZS) via an ordinary ultrasonic self-assembly method combined with calcination to form a novel ZFO@C/CZS catalyst with step-scheme (S-scheme) heterojunction. The photocatalytic hydrogen evolution reaction (HER) was conducted to verify the enhanced photoactivity of ZFO@C/CZS. The optimal ZFO@C/CZS exhibits an extraordinary photocatalytic HER rate of 111.3 ± 0.9 mmol g-1 h-1 under visible-light irradiation, corresponding to an apparent quantum efficiency as high as (76.2 ± 0.9)% at 450 nm. Additionally, the as-synthesized ZFO@C/CZS composite exhibits high stability and recyclability. The excellent photocatalytic hydrogen evolution performance should arise from the formed S-scheme heterojunction and the unique ZFO@C core-shell structure, which inhibit electron hole recombination as well as provide more reactive sites. The pathway of S-scheme charge transfer was validated through density functional theory calculations and electrochemical measurements. This work provides a rational strategy for the synthesis of unique magnetic S-scheme heterojunction photocatalysts for water splitting under visible light irradiation.