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Photocatalytic activity is mainly limited by recombination of photogenerated carriers and insufficient active sites, which would restrain the efficiency of photocatalytic redox reactions. Herein, 2D/0D heterojunctions of Bi2MoO6 nanosheets/BN quantum dots (BM/BNQDs) were prepared via a simple hydrothermal method, which exhibited enhanced photocatalytic performance for the tetracycline (TC) degradation under visible-light irradiation. Combing small-size BNQDs in the average diameter of ~ 5 nm with BM nanosheets displayed tremendous advantages such as rapid charge transport and sufficient active sites. Notably, the as-synthesized BNQDs acting as the photoinduced hole extractors effectively dispersed photogenerated holes and electrons, facilitating the apparent rate constant exhibited by the BM/2BNQDs catalyst 3.1 times that of pure BM. Moreover, PL and electrochemical test results indicated that the separation and transfer of photogenerated charge carriers were enhanced after introducing BNQDs in BM nanosheets. And this work is expected to provide design ideas and insights for the development of efficient photocatalysts based on 2D/0D nanocomposites.

Typically, Z-scheme heterojunctions with excellent photodegradation capability need electron mediator to assist electron transfer, such as redox water mediator and noble metal nanoparticles, but redox water mediators usually cause weak photoabsorption capability and constancy of the photocatalyst, and the noble metal nanoparticles as electron transfer mediator are costly and suffer from various reverse reactions between the redox mediators and the photocatalysts. In this work, oxygen vacancies (OVs)-assisting 2D/2D Z-scheme BiO1-XBr/g-C3N4 (OV-BOB-CN) photocatalysts were synthesized successfully via a simple hydrothermal treatment. Notably, the introduction of OVs is not only to improve visible-light absorption capacity of photocatalyst reflected by UV–vis DRS, but more importantly, it can act as electron mediator in capturing and shuttling electrons of Z-scheme heterostructure to accelerate the separation rate of photogenerated carriers, which was demonstrated by transient photocurrent analysis, EIS, and PL results. The suitable ratio of OV-BOB-CN (OV-50BOB-50CN) showed optimal photodegradation activity for RhB, which was mainly owed to the synergistic reaction between 2D/2D Z-scheme heterostructure and OVs. The photocatalytic mechanism of OV-BOB-CN was revealed by free radical trapping experiments. In conclusion, this work provided a new protocol to design 2D/2D Z-scheme photocatalyst involved OVs, thus guiding a new way to further enhance degradation activity of photocatalyst.

A series of novel 2D/2D Z-scheme visible-light-driven g-C3N4/Au/Bi2WO6 (CN/Au/BWO) photocatalysts were fabricated via a photoreduction and hydrothermal reaction process. The microscopic mechanisms of interface interaction, charge transfer and separation, as well as the influence on the photocatalytic activity of CN/Au/BWO composite were systematic investigated. The photocatalytic performance of CN/Au/BWO photocatalysts was evaluated by the photodegradation of Rhodamine B under visible-light illumination. The results showed that CN/Au(1)/BWO displayed the optimum photocatalytic activity, which was 1.48 times and 1.62 times as that of Bi2WO6 nanosheets and g-C3N4, respectively. The improved photocatalytic activity of CN/Au/BWO could be mainly attributed to the construction of 2D/2D Z-scheme architectures, which not only provided abundant active sites but also effectively improved the separation rate of photogenerated carriers. It was noted that Au nanoparticles acted as a redox mediator in the Z-scheme heterostructure between Bi2WO6 and g-C3N4 to promote the transmission and separation of photo-generated electrons and holes in the middle of Bi2WO6 and g-C3N4. A possible photocatalytic reaction mechanism of photocatalytic RhB degradation over CN/Au/BWO was tentatively proposed through active species trapping experiments. In summary, the current study could provide a new insight for designing effective 2D/2D Z-scheme photocatalysts to guide the further improvement of their photocatalytic activity.

“Atomic” intercalation of magnesium (Mg) in mesoporous silica hollow spheres which are composed of ultrathin nanosheets with several nanometers in width has been achieved through a one-pot hydrothermal synthesis process. The highly dispersed state of Mg in the silica hollow spheres leads to the creation of more complicated shell morphology with higher surface area and larger pore volume than the silica hollow spheres without Mg. With the Mg intercalation, the structure may provide not only suitable spaces but also surface functions for the adsorption of various organic pollutants. In the removal of dyes (cationic or anionic) in the water solution, the Mg intercalated silica spheres showed much higher adsorption capacity in contrast to the silica hollow spheres without Mg. The removal efficiency can also be well maintained for repeated usage after the recovery. The work presents a new strategy to obtain silica spheres with highly homogeneously dispersed Mg and also may further promote the potential applications of hybrid silica materials in catalysis, drug delivery, and biosensing etc.