The development of advanced air transportation has raised new demands for high-performance liquid hydrocarbon fuels. However, the measurement of fuel properties is time-consuming, cost-intensive, and limited to the operating conditions. The physicochemical properties of aerospace fuels are directly influenced by chemical composition. Thus, a thorough investigation should be conducted on the inherent relationship between fuel properties and composition for the design and synthesis of high-grade fuels and the prediction of fuel properties in the future. This work summarized the effects of fuel composition and hydrocarbon molecular structure on the fuel physicochemical properties, including density, net heat of combustion (NHOC), low-temperature fluidity (viscosity and freezing point), flash point, and thermal-oxidative stability. Several correlations and predictions of fuel properties from chemical composition were reviewed. Additionally, we correlated the fuel properties with hydrogen/carbon molar ratios (n _H/C) and molecular weight (M). The results from the least-square method implicate that the coupling of H/C molar ratio and M is suitable for the estimation of density, NHOC, viscosity and effectiveness for the design, manufacture, and evaluation of aviation hydrocarbon fuels.

Water pollution is a global environmental issue with multi-dimensional influences on human life. Some strategies, such as photo-Fenton reaction, have been employed to remove recalcitrant pollutants. Two-dimensional (2D) graphene and its three-dimensional (3D) configurations have attracted considerable attention as emerging carbon-based catalysts in photo-Fenton fields owing to their alluring properties in electron transfer, reactant adsorption, and light response. This review summarizes the recent developments in 2D and 3D graphene-based catalysts for photo-Fenton reactions. Their structures, characteristics, activity, and mechanisms are discussed. The conclusions and outlooks are proposed for the profound understanding of challenges and future directions.

Metal–organic frameworks (MOFs) and layered double hydroxides (LDHs) have been considered to be one of the most promising and worthy hot spot materials to develop advanced catalysts for efficient hydrogen evolution due to their prominent characteristics, including unique structures, environmentally friendly nature, high redox activities, and homogeneously effective utilization of transition metal atoms. In this work, the delicate S-scheme heterojunction photocatalyst, CoAl LDH@Ni-MOF-74, was rationally designed and successfully constructed by coupling Ni-MOF-74 with CoAl LDH based on their peculiar structure, excellent electronic properties, and opposite surface potential for enhancing hydrogen generation activity under visible light irradiation. The CoAl LDH nanolayers evenly and dispersedly load on the surface of Ni-MOF-74. The CoAl LDH@Ni-MOF-74 exhibited higher photocatalytic hydrogen evolution activity compared with Ni-MOF-74 and CoAl LDH alone, mainly because the formation of the CoAl LDH@Ni-MOF-74 S-scheme heterojunction accelerated the recombination of several electrons (from conduction band (CB) of Ni-MOF-74) and holes (from valence band (VB) of CoAl LDH) and prevented the recombination of other electrons (from CB of CoAl LDH) and holes (from VB of Ni-MOF-74).

Photocatalytic hydrogen evolution is an attractive field for future environment-friendly energy. However, fast recombination of photogenerated charges severely inhibits hydrogen efficiency. Single-atom cocatalysts such as Pt have emerged as an effective method to enhance the photocatalytic activity by introduction of active sites and boosting charge separation with low-coordination environment. Herein, we demonstrated a new strategy to develop a highly active Pd single atom in carbon-deficient g-C₃N₄ with a unique coordination. The single-atom Pd–N₃ sites constructed by oil bath heating and photoreduction process were confirmed by HADDF-STEM and XPS measurements. Introduction of single-atom Pd greatly improved the separation and transportation of charge carriers, leading to a longer lifespan for consequent reactions. The obtained single-atom Pd loaded on the carbon-deficient g–C₃N₄ showed excellent photocatalytic activity in hydrogen production with about 24 and 4 times higher activity than that of g–C₃N₄ and nano-sized Pd on the same support, respectively. This work provides a new insight on the design of single-atom catalyst.

NH₂-UIO66 (NU) is a promising photocatalyst for the reduction of Cr(VI) to low-toxic Cr(III) driven by visible light under ambient conditions. However, the main limitation in this process is the inefficient ligand to metal charge transfer (LMCT) of photo-excited electrons, which is caused by inherent energy gap (ΔE _LMCT). This study synthesized the defective NU (NUX-H, where X is the molar equivalent of the modulator) with reduced ΔE _LMCT through linkers removal via acid treatment. The electronic structure of NUX-H was systematically investigated, and the results indicated that the structural defects in NUX-H strongly altered the environment of the Zr atoms. Furthermore, they substantially lowered the energy of the unoccupied d orbitals (LUMO), which was beneficial to efficient LMCT, resulting in an improved photocatalytic activity of NUX-H toward high-concentration (100 mg/L) Cr(VI) reduction. Compared to NU with defect-free structure, the reducing rate of Cr(VI) was increased by 47 times. This work introduced an alternative strategy in terms of designing efficient photocatalysts for reducing Cr(VI) under ambient conditions.

BiOCl has been used in the photoreduction of CO₂, but exhibits limited photocatalytic activity. In this study, Bi was in situ reduced and deposited on the surface of (001)-dominated BiOCl nanosheets by NaBH₄ to form Bi/BiOCl nanosheets enriched with oxygen vacancies. The as-prepared Bi/BiOCl nanosheets having low thickness (ca. 10 nm) showed much higher concentration of oxygen vacancies compared to Bi/BiOCl nanoplates having high thickness (ca. 100 nm). Subsequently, the photocatalytic activity of the Bi/BiOCl nanosheets enriched with oxygen vacancies for CO₂ reduction was dramatically enhanced and much higher than that of BiOCl nanoplates, nanosheets, and Bi/BiOCl nanoplates. It showed that the improved photocatalytic activity in the reduction of CO₂ can be attributed to the enhanced separation efficiency of photogenerated electron–hole pairs of the oxygen vacancies on BiOCl nanosheets and Bi metals. This work demonstrated that the in situ reduction of non-noble metals on the surface of BiOCl nanosheets that are enriched with oxygen vacancies is favorable for increasing photocatalytic CO₂ reduction.