Cocatalyzing Pt/PtO Phase-Junction Nanodots on Hierarchically Porous TiO2 for Highly Enhanced Photocatalytic Hydrogen Production

Combined effects of Pt nanoparticles and oxygen vacancies to promote photothermal catalytic degradation of toluene

Pt/Mn-TiO₂ photothermal catalysts with abundant oxygen vacancies are prepared by loading Pt onto a composite of MnO_x and TiO₂ using MIL-125 as precursor (abbreviated as Mn-TiO₂) and subsequent hydrogen reduction treatment. Under light irradiation with intensity of 625 mW/cm², the optimal 0.65Pt/Mn-TiO₂ catalyst can achieve toluene conversion of 90.4 % and CO₂ yield of 85.6 %, respectively, and maintain stable activity for at least 30 h in the presence of coke and water. The introduction of Pt nanoparticles improves the utilization of solar spectrum and facilitates the generation of more oxygen vacancies. The comparative experiments of photothermal catalysis and thermal catalysis further verify that light not only acts as a heat source but also enhances catalytic reaction through photocatalysis and photoactivation of lattice oxygen. In the follow-up work, catalytic oxidation under natural sunlight is performed on 0.65Pt/Mn-TiO₂ to reach 75.0 % of toluene conversion, displaying a good practical application potential.

Electrospun Donor/Acceptor Nanofibers for Efficient Photocatalytic Hydrogen Evolution

We prepared a series of one-dimensional conjugated-material-based nanofibers with different morphologies and donor/acceptor (D/A) compositions by electrospinning for efficient photocatalytic hydrogen evolution. It was found that homogeneous D/A heterojunction nanofibers can be obtained by electrospinning, and the donor/acceptor ratio can be easily controlled. Compared with the single-component-based nanofibers, the D/A-based nanofibers showed a 34-fold increase in photocatalytic efficiency, attributed to the enhanced exciton dissociation in the nanofibrillar body. In addition, the photocatalytic activity of these nanofibers can be easily optimized by modulating the diameter. The results show that the diameter of the nanofibers can be conveniently controlled by the electrospinning feed rate, and the photocatalytic effect increases with decreasing fiber diameter. Consequently, the nanofibers with the smallest diameter exhibit the most efficient photocatalytic hydrogen evolution, with the highest release rate of 24.38 mmol/(gh). This work provides preliminary evidence of the advantages of the electrospinning strategy in the construction of D/A nanofibers with controlled morphology and donor/acceptor composition, enabling efficient hydrogen evolution.

PtCu alloy cocatalysts for efficient photocatalytic CO2 reduction into CH4 with 100% selectivity

In this paper, PtCu alloys with varying Pt/Cu ratios were deposited onto TiO2 nanocrystals to selectively photoreduce CO2 into CH4.

Nickel clusters accelerating hierarchical zinc indium sulfide nanoflowers for unprecedented visible-light hydrogen production

As a typical two-dimensional (2D) metal chalcogenides and visible-light responsive semiconductor, zinc indium sulfide (ZnIn₂S₄) has attracted much attention in photocatalysis. However, the high recombination rate of photogenerated electrons and holes seriously limits its performance for hydrogen production. In this work, we report in-situ photodeposition of Ni clusters in hierarchical ZnIn₂S₄ nanoflowers (Ni/ZnIn₂S₄) to achieve unprecedented photocatalytic hydrogen production. The Ni clusters not only provide plenty of active sites for reactions as evidenced by in-situ photoluminescence measurement, but also effectively accelerate the separation and migration of the photogenerated electrons and holes in ZnIn₂S₄. Consequently, the Ni/ZnIn₂S₄ composites exhibit good stability and reusability with highly enhanced visible-light hydrogen production. In particular, the best Ni/ZnIn₂S₄ photocatalyst exhibits an unprecedented hydrogen production rate of 22.2 mmol·h^-1·g^-1, 10.6 times that of the pure ZnIn₂S₄ (2.1 mmol·h^-1·g^-1). And its apparent quantum yield (AQY) is as high as 56.14% under 450 nm monochromatic light. Our work here suggests that depositing non-precious Ni clusters in ZnIn₂S₄ is quite promising for the potential practical photocatalysis in solar energy conversion.

Reversed selectivity of photocatalytic CO2 reduction over metallic Pt and Pt(II) oxide cocatalysts

The chemical state of Pt in cocatalysts has a major influence on the activity and selectivity of the photocatalytic reduction of CO2; however, the underlying mechanism is unclear owing to the co-existence of different Pt chemical states and mutual transformation between them. In this study, PtO/TiO2 catalysts were prepared through photodeposition and Pt/TiO2 was prepared by the photoreduction of PtO/TiO2 to avoid interference arising from co-existing Pt forms and different loading amounts. These catalysts exhibited completely reversed selectivity for CO and CH4 production during CO2 photoreduction: PtO/TiO2 tended to produce CO (100%), whereas Pt/TiO2 favored the production of CH4 (66.6%). By combining experimental analysis and theoretical calculations, the difference in selectivity was ascribed to the different charge transfer/separation and CO/H adsorption properties of PtO/TiO2 and Pt/TiO2. Photoelectric and photoluminescence (PL) analysis showed that Pt was more advantageous to the photogenerated carrier separation compared with PtO, which was conducive to the multi-electron CH4 reduction reaction. Fourier transform-infrared spectroscopy, temperature-programmed desorption/temperature-programmed reduction, and density functional theory calculations indicated that the adsorption of CO and hydrogen on Pt was stronger than that on PtO, which favored the further reduction of CO to CH4. Based on the above results, a mechanism was proposed to explain the reversed selectivity of the photocatalytic reduction of CO2 over Pt/TiO2 and PtO/TiO2.

Controllable fabrication of TiO2 anatase/rutile phase junctions by a designer solvent for promoted photocatalytic performance

Highly active coin tree-like TiO₂ anatase–rutile phase junctions were constructed by tailored DESs and the two-phase ratios can be easily tuned.

In Situ Synthesis of Mesoporous TiO2 Nanofibers Surface-Decorated with AuAg Alloy Nanoparticles Anchored by Heterojunction Exhibiting Enhanced Solar Active Photocatalysis

We designed an electrospinning synthesis protocol to obtain in situ, the mesoporous TiO₂ nanofibers, which are surface-decorated with plasmonic AuAg nanoparticles (AuAg-mTNF-H). Such alloy nanoparticles are found to be partially exposed on the surface of the nanofibers. Characterization by HRTEM and EDS confirmed the formation of 1:1 AuAg alloy nanoparticles on the surface of TiO₂ nanofibers with heterojunction at the interfaces. On the basis of electron microscopic characterization, we proposed that, during the formation of the nanofibers, the incorporated metal ions with surface capping of negative charges migrated toward the outer surface of the nascent fibers under the influence of high positive voltage required for electrospinning. As a result, after the subsequent thermal treatment, the crystallization of TiO₂ nanofibers and the formation of alloy nanoparticles took place, leading to the formation of a deep heterojunction through partial embedment of the nanoparticles. The formation of AuAg alloy also restricted the oxidation of Ag, thus making the nanoparticles highly stable in ambient condition. Accordingly, such unique AuAg-mTNF-H photocatalyst shows strong light absorption property covering the entire range of visible wavelengths with stability. The solar light harvesting property of AuAg-mTNF-H was verified by monitoring solar light induced H₂ evolution via water splitting and photodecomposition of MB. In both the cases AuAg-mTNF-H showed excellent H₂ evolution and photodecomposition of dye.

A robust CdS/In2O3 hierarchical heterostructure derived from a metal–organic framework for efficient visible-light photocatalytic hydrogen production

CdS/In₂O₃ hierarchical nanotubes with intimate and extensive contact between CdS and In₂O₃ were synthesized from a MOF and showed huge improvement of visible-light photocatalytic hydrogen production.

Hydrothermally Induced Oxygen Doping of Graphitic Carbon Nitride with a Highly Ordered Architecture and Enhanced Photocatalytic Activity

As an amorphous or semicrystalline material, graphitic carbon nitride (g-C₃ N₄ ) displays poor photocatalytic activity owing to rapid recombination of the photogenerated charge carriers, which is mainly caused by a high density of defects in the graphitic structure. In this work, a porous O-doped g-C₃ N₄ (P-CNO) nanosheet with a highly ordered architecture is fabricated by introducing a novel hydrothermal treatment to the precursor before the final thermal condensation. The photocatalytic hydrogen evolution rate (HER) and HER per surface area of P-CNO are 13.9 and 1.7 times higher than that of bulk g-C₃ N₄ . The improved photocatalytic activity is ascribed to a synergistic effect of O doping, a porous sheet-like morphology, and increased crystallinity. This work also provides a new approach for the synthesis of other polymer-based photocatalysts with high crystallinity and excellent performance.

Three-dimensionally ordered macroporous Sn4+-doped TiO2 with anatase–rutile mixed phase via Pt loading by photoreduction method: enhanced photodegradation and hydrogen production performance

3DOM Pt/Sn–TiO₂ with anatase–rutile mixed phase was successfully prepared by the colloidal crystal template method and the photoreduction method. A series of photocatalytic experiments showed that 3DOM Pt/Sn–TiO₂ exhibited significant photocatalytic activity in photodegradation and water splitting.

The three-dimensional ordered macroporous structure of the Pt/TiO2–ZrO2 composite enhanced its photocatalytic performance for the photodegradation and photolysis of water

Using polystyrene (PS) spheres as a template, three-dimensional ordered macroporous Pt/TiO₂–ZrO₂ (3DOM Pt/TiO₂–ZrO₂) composites were prepared by vacuum impregnation combined with photoreduction. The crystal structure, composition, morphology, optical absorption, and surface physicochemical properties of the as-synthetized samples were characterized by X-ray diffraction (XRD), UV-visible diffuse reflectance spectroscopy (UV-vis/DRS), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and N₂ adsorption–desorption analyses. The results showed that the 3DOM Pt/TiO₂–ZrO₂ composites were mainly composed of anatase TiO₂ and tetragonal ZrO₂ crystal phases, in which Pt mainly existed as a single species. In addition, the as-synthesized composites had open, three-dimensionally ordered macroporous structures that could enhance their multi-mode photocatalytic degradation performance under UV, visible light, simulated solar light, and microwave-assisted irradiation. Moreover, the 3DOM Pt/TiO₂–ZrO₂ composites exhibited the best photocatalytic water splitting performance as compared to other systems.

Using polystyrene spheres as templates, 3DOM Pt/TiO₂–ZrO₂ composites were prepared by the vacuum impregnation combined with photoreduction method, which exhibited an enhanced photodegradation and water splitting performance.