Visible-Light-Driven Photocatalytic H2 Production from H2O Boosted by Hydroxyl Groups on Alumina

D-A Conjugated Polymer/CdS S-Scheme Heterojunction with Enhanced Interfacial Charge Transfer for Efficient Photocatalytic Hydrogen Generation

Owing to the improved charge separation and maximized redox capability of the system, Step-scheme (S-scheme) heterojunctions have garnered significant research attention for efficient photocatalysis of H2 evolution. In this work, an innovative linear donor-acceptor (D-A) conjugated polymer fluorene-alt-(benzo-thiophene-dione) (PFBTD) is coupled with the CdS nanosheets, forming the organic-inorganic S-scheme heterojunction. The CdS/PFBTD (CP) composite exhibits an impressed hydrogen production rate of 7.62 mmol g-1 h-1 without any co-catalysts, which is ≈14 times higher than pristine CdS. It is revealed that the outstanding photocatalytic performance is attributed to the formation of rapid electron transfer channels through the interfacial Cd─O bonding as evidenced by the density functional theory (DFT) calculations and in situ X-ray photoelectron spectroscopy (XPS) analysis. The charge transfer mechanism involved in S-scheme heterojunctions is further investigated through the photo-irradiated Kelvin probe force microscopy (KPFM) analysis. This work provides a new point of view on the mechanism of interfacial charge transfer and points out the direction of designing superior organic-inorganic S-scheme heterojunction photocatalysts.

Excellent Charge Separation of NCQDs/ZnS Nanocomposites for the Promotion of Photocatalytic H2 Evolution

Carbon Quantum dots (CQDs) are widely studied because of their good optical and electronic characteristics and because they can easily generate photocarriers. Nitrogen-doped CQDs (NCQDs) may exhibit improved hydrophilic, optical, and electron-transfer properties, which are conducive to photocatalytic hydrogen evolution. In this paper, NCQD-modified ZnS catalysts were successfully prepared. Under the irradiation of the full spectrum, the H2 evolution rate of the optimal catalyst 0.25 wt % NCQDs/ZnS achieves 5.70 mmol g-1 h-1, which is 11.88, 43.84, and 5.14 times the values of ZnS (0.48 mmol g-1 h-1), NCQDs (0.13 mmol g-1 h-1), and CQDs/ZnS (1.11 mmol g-1 h-1), respectively. Furthermore, it shows good stability, indicating that the modification of NCQDs prevents the photocorrosion and oxidation of ZnS. The enhanced performance is due to NCQD loading, which promotes the separation of photogenerated carriers, optimizes the structures, and increases the specific surface area. This work highlights the fact that NCQD-modified ZnS may afford a new strategy to synthesize ZnS-based photocatalysts with enhanced H2 production performance.

Augmented photocatalysis induced by 1T-MoS2 bridged 2D/2D MgIn2S4@1T/2H-MoS2 Z-scheme heterojunction: mechanistic insights into H2O2 and H2 evolution

In the realm of composite photocatalysts, the fusion of the co-catalyst effect with interfacial engineering is recognized as a potent strategy for facilitating the segregation and migration of photo-induced charge carriers. Herein, an innovative mediator-based Z-scheme hybrid, i.e. MIS@1T/2H-MoS2, has been well designed by pairing MIS with 1T/2H-MoS2via a facile hydrothermal strategy as a competent photocatalyst for H2O2 and H2 generation. The co-catalyst, i.e. metallic 1T-phase bridging between semiconducting 2H-MoS2 and MIS, serves as a solid state electron mediator in the heterostructure. Morphological findings revealed the growth of 1T/2H-MoS2 nanoflowers over MIS microflowers, verifying the close interaction between MIS and 1T/2H-MoS2. By virtue of accelerated e-/h+ pair separation and migration efficiency along with a proliferated density of active sites, the MMoS2-30 photocatalyst yields an optimum H2O2 of 35 μmol h-1 and H2 of 370 μmol h-1 (ACE of 5.9%), which is 3 and 2.7 fold higher than pristine MIS. This obvious enhancement can be attributed to photoluminescence and electrochemical aspects that substantiate the diminished charge transfer resistance along with improved charge carrier separation, representing a good example of a noble metal-free photocatalyst. The proposed Z-scheme charge transfer mechanism is aided by time-resolved photoluminescence (TRPL), XPS, radical trapping experiments, and EPR analysis. Overall, this endeavour provides advanced insights into the architecture of noble metal-free Z-scheme heterostructures, offering promising prospects in photocatalytic applications.

Electronic Interactions on Platinum/(Metal-Oxide)-Based Photocatalysts Boost Selective Photoreduction of CO2 to CH4

By supporting platinum (Pt) and cadmium sulfide (CdS) nanoparticles on indium oxide (In2 O3 ), we fabricated a CdS/Pt/In2 O3 photocatalyst. Selective photoreduction of carbon dioxide (CO2 ) to methane (CH4 ) was achieved on CdS/Pt/In2 O3 with electronic Pt-In2 O3 interactions, with CH4 selectivity reaching to 100 %, which is higher than that on CdS/Pt/In2 O3 without electronic Pt-In2 O3 interactions (71.7 %). Moreover, the enhancement effect of electronic Pt-(metal-oxide) interactions on selective photoreduction of CO2 to CH4 also occurs by using other common metal oxides, such as photocatalyst supports, including titanium oxide, gallium oxide, zinc oxide, and tungsten oxide. The electronic Pt-(metal-oxide) interactions separate photogenerated electron-hole pairs and convert CO2 into CO2 δ- , which can be easily hydrogenated into CH4 via a CO2 δ- →HCOO*→HCO*→CH*→CH4 path, thus boosting selective photoreduction of CO2 to CH4 . This offers a new way to achieve selective photoreduction of CO2 .