Non-precious molybdenum nanospheres as a novel cocatalyst for full-spectrum-driven photocatalytic CO2 reforming to CH4.

Photocatalytic CO2 reforming is considered to be an effective method for clean, low-cost, and environmentally friendly reduction and conversion of CO2 into hydrocarbon fuels by utilizing solar energy. However, the low separation efficiency of charge carriers and deficient reactive sites have severely hampered the efficiency of the photocatalytic CO2 reforming process. Therefore, cocatalysts are usually loaded onto the surface of semiconductor photocatalysts to reduce the recombination of charge carriers and accelerate the rates of surface reactions. Herein, molybdenum (Mo) nanospheres are proposed as a novel non-precious cocatalyst to enhance the photocatalytic CO2 reforming of g-C3N4 significantly. The Mo nanospheres boost the adsorption of CO2 and activate the surface CO2via a photothermal effect. The time-resolved fluorescence decay spectra reveals that the lifetime of photo-induced charge carriers is prolonged by the Mo nanospheres, which guarantees the migration of charge carriers from g-C3N4 to Mo nanospheres. Unexpectedly, Mo loaded g-C3N4 can effectively utilize a wide spectral range from UV to near-infrared region (NIR, up to 800 nm). These findings highlight the potential of Mo nanospheres as a novel cocatalyst for photocatalytic CO2 reforming to CH4.

Enhanced Photocatalytic CO2 Reduction in Defect-Engineered Z-Scheme WO3-x /g-C3N4 Heterostructures.

Oxygen vacancy-modified WO3-x nanorods composited with g-C3N4 have been synthesized via the chemisorption method. The crystalline structure, morphology, composition, band structure, and charge separation mechanism for WO3-x /g-C3N4 heterostructures are studied in detail. The g-C3N4 nanosheets are attached on the surface of WO3-x nanorods. The Z-scheme separation is confirmed by the analysis of generated hydroxyl radicals. The electrons in the lowest unoccupied molecular orbital of g-C3N4 and the holes in the valence band of WO3 can participate in the photocatalytic reaction to reduce CO2 into CO. New energy levels of oxygen vacancies are formed in the band gap of WO3, further extending the visible-light response, separating the charge carriers in Z-scheme and prolonging the lifetime of electrons. Therefore, the WO3-x /g-C3N4 heterostructures exhibit much higher photocatalytic activity than the pristine g-C3N4.

Fabrication of ZnO/Red Phosphorus Heterostructure for Effective Photocatalytic H2 Evolution from Water Splitting.

Photocatalysis is a green technique that can convert solar energy to chemical energy, especially in H2 production from water splitting. In this study, ZnO and red phosphorus (ZnO/RP) heterostructures were fabricated through a facile calcination method for the first time, which showed the considerable photocatalytic activity of H2 evolution. The photocatalytic activities of heterostructures with different ratios of RP have been investigated in detail. Compared to bare ZnO, ZnO/RP heterostructures exhibit a 20.8-fold enhancement for H2 production and furthermore overcome the photocorrosion issue of ZnO. The improved photocatalytic activities highly depend on the synergistic effect of the high migration efficiency of photo-induced electron⁻hole pairs with the inhibited charge carrier recombination on the surface. The presented strategy can also be applied to other semiconductors for various optoelectronics applications.

Stannous oxide promoted charge separation in rationally designed heterojunction photocatalysts with a controllable mechanism.

Due to the sluggish mobility of holes, the low charge-separation rate remains an intrinsic issue that limits further increase of the photocatalytic conversion efficiency. Herein, we proposed an in situ hydrothermal method to expedite the charge transfer with enhanced photocatalytic H2 evolution rate and photodegradation activities via introducing SnO microplates into TiO2. As compared to bare TiO2, the SnO/TiO2 heterojunction achieves remarkable 470% and 150% higher efficiency for the photocatalytic H2 evolution rate and photodegradation of rhodamine B, respectively. In particular, it is demonstrated that the charge transfer mechanism of SnO/TiO2 can be switched from the Z-scheme to type II by Pt loading, leading to a significant enhancement of photocatalytic performances. Furthermore, the photocatalytic H2 evolution activities of ZnO and C3N4 can also be improved by introducing SnO via simple mechanical mixing. This work provides not only a new versatile stimulant for enhancing photocatalytic activities but also in-depth understanding of the charge transfer mechanism of heterointerfaces of semiconductors.