TiO₂ Quantum Dots/Fe₃S₄ Heterojunction Nanocomposites for Efficient Ammonia Production through Nitrogen Fixation upon Simulated Sunlight

Abstract

Using semiconductor photocatalysts instead of the traditional Haber−Bosch procedure to produce ammonia is a promising strategy to save energy and prevent environmental pollution. Therefore, finding a suitable photocatalyst with high efficiency and stability has become one of the big challenges of research communities in the field of heterogeneous photocatalysis. Herein, S-scheme TiO 2 quantum dots (QDs)/Fe 3 S 4 heterojunction photocatalysts were synthesized through a hydrothermal route. The nitrogen photofixation measurements exhibited that the TiO 2 QDs/Fe 3 S 4 photocatalysts have excellent activities, where the generation of NH 3 by the optimized nanocomposite reached 16,624 μmol L −1 g −1 upon simulated sunlight. This amount was almost 19.9, 6.30, and 2.85 times as high as those of TiO 2 , TiO 2 QDs, and Fe 3 S 4 photocatalysts, respectively. The promoted photocatalytic ability was devoted to outstanding visiblelight absorption, accelerated segregation of photoinduced electron−hole pairs, and enhanced surface area. The key purpose of this research was the rational design of a photocatalyst based on TiO 2 QDs through a one-pot and facile fabrication procedure, which exhibits admirable performance in the field of photocatalytic nitrogen fixation. Considering the advantages of binary TiO 2 QDs/ Fe 3 S 4 photocatalysts, it is anticipated that this photocatalyst could be utilized in solar energy conversion processes.

Incorporation of Cu5FeS4 QDs with Abundant Oxygen Vacancy TiO2 QDs/TiO2 OVs: Double S-Scheme Photocatalysts for Effectual N2 Conversion to NH3 under Simulated Solar Light

“…The TiO 2 OVs, TiO 2 QDs, and Cu 5 FeS 4 are n-type, n-type, and p-type semiconductors, respectively. So, in the first two semiconductors, the Fermi levels ( E F ) are close to the CB, and in the later one, the E F is close to the VB. ,, After integration of TiO 2 QDs, TiO 2 OVs, and Cu 5 FeS 4 , double S-scheme hetero/homo junctions are formed between them. The electron transfer takes place from the semiconductor having a more negative E F .…”

Decoration of Carbon Dots on Oxygen-Vacancy-Enriched S-Scheme TiO2 Quantum Dots/TiO2 Oxygen Vacancies Photocatalysts: Impressive Quantum-Dot-Sized Photocatalysts for Remediation of Antibiotics, Bacteria, and Dyes

“…The S-scheme mechanism is proposed on the basis of the energy band structure over TQDs/TOVs/C-dots photocatalysts, as depicted in Figure c. The energy gaps and energy band positions for TiO 2 QDs and TiO 2 OVs semiconductors have been calculated from Mott–Schottky analyses in our previous work. , When the type-II heterojunction is established between the components, electrons are transferred from the conduction band (CB) of TiO 2 QDs to that of TiO 2 OVs and holes are transferred from the valence band (VB) of TiO 2 OVs to that of TiO 2 QDs. Although the segregation of electrons from holes occurs efficiently in a type-II heterojunction system, the movement of electrons and holes is associated with coulombic repulsion force .…”

Schottky Junctions with Bi@Bi2MoO6 Core-Shell Photocatalysts toward High-Efficiency Solar N2-to-Ammonnia Conversion in Aqueous Phase

“…However, the efficiency of this process still has a wide gap compared to that of the Haber-Bosch one due to the difficulty of N 2 activation and the quick recombination of photo-generated carriers [11][12][13]. The strategies of innovative fabrication for functional material design, including defect and dopant engineering, heterojunction construction by integrating a semiconductor and metal or another semiconductor, reactive crystal facet exposure and so on, have been widely explored [14][15][16][17]. The purpose mainly focuses on the functionality that not only facilitates the separation of photo-excited electrons and holes but also provides more N 2 activation sites for solar-to-ammonia conversion.…”