Metal oxides have attracted an increasing attention for the photo-degradation of organic containments. Deep understanding of the physical parameters correlated with the photocatalytic process is critical and beneficial for finding an efficient and robust photocatalyst. Herein, by taking SnO₂ as a prototypical model, we systematically study exciton energy, effective mass, carrier mobility and partial charge density based on the density functional theory (DFT). We demonstrate that the obtained exciton energy is quite low and can be effectively dissociated into charge carriers at room temperature. The estimated carrier mobility of electrons is about 50 times greater than that of holes. More interestingly, analyzing partial charge density on the top of the valence band reveals that the photocatalytic oxidation reaction site would occur on the O-p state. Experimentally, SnO₂ nanoparticles have been synthesized by a simple method and characterized by Powder XRD and TEM. With the photocatalyst SnO₂, more than 90% methyl blue (MB) and Rhodamine B (RhB) are degraded under the UV light irradiation within 50 min and 270 min, respectively. Trapping experiments reveal that ˙OH are the main active species to oxidize the organic dye and mainly originate through the oxidation of holes (h⁺). This study establishes an in-depth understanding of electronic structure and photocatalysis and provides insights into the designing of new photocatalytic materials.

Sodium/potassium poly(heptazine imide) (NaK-PHI) with an electron sink effect is synthesized in ternary eutectic salts to improve charge separation and transport efficiency for H₂O₂ production.

The design of highly efficient and stable photocatalysts to utilize solar energy is a significant challenge in photocatalysis. In this work, a series of novel p-n heterojunction photocatalysts, Li₂SnO₃/g-C₃N₄, was successfully prepared via a facile calcining method, and exhibited superior photocatalytic activity toward the photodegradation of Rhodamine B solution under visible light irradiation as compared with pure Li₂SnO₃ and g-C₃N₄. The maximum kinetic rate constant of photocatalytic degradation of Rhodamine B within 60 min was 0.0302 min⁻¹, and the composites still retained excellent performance after four successive recycles. Chemical reactive species trapping experiments and electron paramagnetic resonance demonstrated that hydroxyl radicals (·OH) and superoxide ions ($·{\text{O}}_2^{-}$) were the dominant active species in the photocatalytic oxidation of Rhodamine B solution, while holes (h⁺) only played a minor role. We demonstrated that the enhancement of the photocatalytic activity could be assigned to the formation of a p-n junction photocatalytic system, which benefitted the efficient separation of photogenerated carriers. This study provides a visible light-responsive heterojunction photocatalyst with potential applications in environmental remediation.

Using solar energy to remove antibiotics from aqueous environments via photocatalysis is highly desirable. In this work, a novel type-II heterojunction photocatalyst, MgSn(OH)₆/SnO_2, was successfully prepared via a facile one-pot in situ hydrothermal method at 220 °C for 24 h. The obtained heterojunctions were characterized via powder X-ray diffraction, Fourier-transform infrared spectroscopy, transmission electron microscopy, and ultraviolet-visible diffuse reflectance spectroscopy. The photocatalytic performance was evaluated for photodegradation of tetracycline solution under ultraviolet irradiation. The initial concentration of tetracycline solution was set to be 20 mg/L. The prepared heterojunctions exhibited superior photocatalytic activity compared with the parent MgSn(OH)₆ and SnO₂ compounds. Among them, the obtained MgSn(OH)₆/SnO₂ heterojunction with MgCl₂·6H₂O:SnCl₄·5H₂O = 4:5.2 (mmol) displayed the highest photocatalytic performance and the photodegradation efficiency conversion of 91% could be reached after 60 min under ultraviolet irradiation. The prepared heterojunction maintained its performance after four successive cycles of use. Active species trapping experiments demonstrated that holes were the dominant active species. Hydroxyl radicals and superoxide ions had minor effects on the photocatalytic oxidation of tetracycline. Photoelectrochemical measurements were used to investigate the photocatalytic mechanism. The enhancement of photocatalytic activity could be assigned to the formation of a type-II junction photocatalytic system, which was beneficial for efficient transfer and separation of photogenerated electrons and holes. This research provides an in situ growth strategy for the design of highly efficient photocatalysts for environmental restoration.