Co3O4 modified Mn0.2Cd0.8S with different shells forms p-n heterojunction to optimize energy/mass transfer for efficient photocatalytic hydrogen evolution

A novel photothermal-assisted FeNi2S4@Mn0.3C0.7S S-scheme heterojunction for enhanced photo-catalytic hydrogen evolution

In addition to the intrinsic driving force of photocatalysis, the external thermal field from the photothermal effect can provide additional energy to the photo-catalytic system to improve the photo-catalytic hydrogen-evolution (PHE) efficiency. Herein, based on the results of density functional theory, we designed and constructed a hollow core-shell FeNi2S4@Mn0.3Cd0.7S (NFS@MCS) S-scheme heterojunction with a photothermal effect, thereby realising a significant enhancement of the PHE performance due to the thermal effect, S-scheme heterojunction and hollow core-shell morphology. As a light collector and heat source, the hollow NFS could absorb and convert photons into heat, resulting in the increased local temperature of photocatalyst particles. Moreover, the S-scheme charge path at the interface not only improved the carrier separation efficiency but also retained a higher redox potential. All these are favourable to increase the PHE activity. The PHE tests show that 0.5 %-NFS@MCS exhibits the highest PHE rate of 17.11 mmol·g-1·h-1, 7.7 times that of MCS. Moreover, through a combination of theoretical calculation and experimental evidence, the PHE mechanism of the NFS@MCS system is discussed and clarified in-depth.

Recent advances of modification effect in Co3O4-based catalyst towards highly efficient photocatalysis

Tricobalt tetroxide (Co3O4) has been developed as a promising photocatalyst material for various applications. Several reports have been published on the self-modification of Co3O4 to achieve optimal photocatalytic performance. The pristine Co3O4 alone is inadequate for photocatalysis due to the rapid recombination process of photogenerated (PG) charge carriers. The modification of Co3O4 can be extended through the introduction of doping elements, incorporation of supporting materials, surface functionalization, metal loading, and combination with other photocatalysts. The addition of doping elements and support materials may enhance the photocatalysis process, although these modifications have a slight effect on decreasing the recombination process of PG charge carriers. On the other hand, combining Co3O4 with other semiconductors results in a different PG charge carrier mechanism, leading to a decrease in the recombination process and an increase in photocatalytic activity. Therefore, this work discusses recent modifications of Co3O4 and their effects on its photocatalytic performance. Additionally, the modification effects, such as enhanced surface area, generation of oxygen vacancies, tuning the band gap, and formation of heterojunctions, are reviewed to demonstrate the feasibility of separating PG charge carriers. Finally, the formation and mechanism of these modification effects are also reviewed based on theoretical and experimental approaches to validate their formation and the transfer process of charge carriers.