Facile Synthesis of Novel Redox-Mediator-free Direct Z-Scheme CaIn₂S₄ Marigold-Flower-like/TiO₂ Photocatalysts with Superior Photocatalytic Efficiency

Abstract

Novel redox-mediator-free direct Z-scheme CaIn2S4 marigold-flower-like/TiO2 (CIS/TNP) photocatalysts with different CaIn2S4 weight percentages were synthesized using a facile wet-impregnation method. Uniform hierarchical marigold-flower-like CaIn2S4 (CIS) microspheres were synthesized using a hydrothermal method. Field-emission scanning electron microscopy and transmission electron microscopy analyses suggested that the formation and aggregation of nanoparticles, followed by the growth of petals or sheets and their subsequent self-assembly, led to the formation of the uniform hierarchical marigold-flower-like CIS structures. The photocatalytic degradation efficiency of the direct Z-scheme CIS/TNP photocatalysts was evaluated through the degradation of the pharmaceutical compounds isoniazid (ISN) and metronidazole (MTZ). The direct Z-scheme CaIn2S4 marigold-flower-like/TiO2 (1%-CIS/TNP) photocatalyst showed enhanced performance in the ISN (71.9%) and MTZ (86.5%) photocatalytic degradations as compared to composites with different CaIn2S4 contents or the individual TiO2 and CaIn2S4. A possible enhancement mechanism based on the Z-scheme formed between the CIS and TNP for the improved photocatalytic efficiency was also proposed. The recombination rate of the photoinduced charge carriers was significantly suppressed for the direct Z-scheme CIS/TNP photocatalyst, which was confirmed by photoluminescence analysis. Radical-trapping studies revealed that photogenerated holes (h+), •OH, and O2•- are the primary active species, and suggested that the enhanced photocatalytic efficiency of the 1%-CIS/TNP follows the Z-scheme mechanism for transferring the charge carriers. It was further confirmed by hydroxyl (•OH) radical determination via fluorescence techniques revealed that higher concentration of •OH radical were formed over 1%-CIS/TNP than over bare CIS and TNP. The separation of the charge carriers was further confirmed using photocurrent and electron spin resonance measurements. Kinetic and chemical oxygen demand analyses were performed to confirm the ISN and MTZ degradation. The results demonstrated that the direct Z-scheme CIS/TNP photocatalyst shows superior decomposition efficiency for the degradation of these pharmaceuticals under the given reaction conditions.

Hydrothermal synthesis of In2O3 nanoparticles hybrid twins hexagonal disk ZnO heterostructures for enhanced photocatalytic activities and stability

“…However, PL intensities of the samples show an opposite variation tendency. This result indicates that an appropriate amount of In 2 O 3 in the composites was beneficial to the fast separation of photo-generated charge carriers and thus enhanced the photocatalytic activity [5, 37]. …”

Platinum Nanoparticles Supported on TiO2 Photonic Crystals as Highly Active Photocatalyst for the Reduction of CO2 in the Presence of Water

“…In addition, in our previous work, we already demonstrated that carbon in the reduction products comes from CO 2 as reactant using isotope experiments with 13 C-labeled CO 2 . [16,39] Thea bove-mentioned tests indicate that CO 2 as the only carbon source together with photocatalystsa nd light are essentialf or the reaction. As shown in Figure 5, the CH 4 production amounto fc ommercial P25 is 0.772 mmol under light irradiationw ithin 450min whereas the productivity of PC-TiO 2 as support is 1.027 mmol.…”

“…[7] Among the photocatalysts,T iO 2 is the most widely used owing to its cheapness,a vailability,p hotostability, and low toxicity. [8,9] To enhance the efficiency of light harvesting and the electron-hole separation, many modification strategies were proposed recently,s uch as crystale ngineering, [10,11] ion doping, [12] sensitization, [13,14] Z-Scheme construction, [15,16] and depositing noble metals. [17] Dispersing noble metals on stable semiconductors used as co-catalysts has emergeda sap romising method that enhances the overall activity.T he enhanced catalyticp erformances are attributed to the co-catalyst improvingt he absorption of solar irradiation and suppressing the recombination of charge carriers.…”

Self‐Organization of Hyperbranched Polyesters Functionalized with Pyrrolo[2,1‐a]isoquinoline End Groups and Their Fluorescent Recognition of Anthracene and Pyrene

“…[26][27][28][29] However, most reports on the fabrication of flower-like architectures to date have focused on linear polymers [30,31] and metallic oxides. [32][33][34] For example, Gaillard and co-workers reported flower-like poly(ethylene oxide)-based macromolecular architectures obtained by photocrosslinking of self-assembled block copolymers. [35] Visaveliya and Köhler reported the formation of flower-like poly(methyl methacrylate) particles with diameters in the lower micrometer to submicrometer range.…”