Single atom catalysts (SACs) show excellent catalytic performance in selective hydrogenation. Herein, the applications of SACs in the selective hydrogenation of unsaturated bonds are reviewed.

Hydrogenation of furfural to value-added chemical products is largely hindered by its multiple reaction pathways and complicated product distribution. Thus, to selectively achieve the desired products, catalysts with precise catalytic properties are highly required. Herein, a series of PdAg bimetallic nanoparticles (NPs) of similar size and tunable composition supported on activated carbon (Pd₄Ag₁/C, Pd₂Ag₁/C, Pd₁Ag₁/C and Pd₂Ag₃/C) were synthesized in a controlled manner and applied in the selective hydrogenation of furfural. Interestingly, an obvious composition-dependent catalytic performance was observed: upon incrementally increasing the proportion of Ag in PdAg NPs, the hydrogenation selectivity can transform from tetrahydrofurfuryl alcohol (sel. 94% for Pd₄Ag₁/C) to furfuryl alcohol (sel. 95% for Pd₁Ag₁/C) with nearly complete conversion (99%) of furfural. DFT calculations revealed that the adsorption free energy of in situ generated furfuryl alcohol on Pd(111) surface is inversely proportional correlated with the Ag content in PdAg bimetallic NPs, which accounts for the alteration of chemoselectivity. Importantly, the present study is the first demonstration of composition-induced selectivity reversal for the hydrogenation of furfural under ambient conditions (25 °C, 0.1 MPa H₂).

Benefiting from the unique electronic and structural characteristics, transition metal and nitrogen co-doped carbon-based (M–N–C) nanomaterials are considered to be one of the most promising catalysts. The combination of uniformly dispersed Cu sites and N-doped carbon materials has enabled Cu–N–C SACs to show outstanding performances in many catalytic fields. However, the adjustment of their coordination environment, the influence of carrier materials and their dynamic evolution in the catalytic process still remain unclear, which limits the application of Cu–N–C SACs. Thus, it is of great significance and urgent to deeply understand the reaction mechanism of Cu–N–C SACs in different catalytic fields. This review focuses on the preparation strategy, regulation mechanism of the coordination environment, catalytic performance and dynamic evolution process of Cu–N–C SACs. Combined with a series of in situ/operando characterization methods, the changes in their coordination and structure in the catalytic process is highlighted. Finally, the prospects of active machine learning, coordination structure identification and determination of real active sites are presented. This review aims to provide a reference for the rational design of Cu–N–C SACs and the exploration of their catalytic mechanism.

Coarse wool is a kind of goat wool that is difficult to further process in the textile industry due to its large diameter, dispersion, better strength, and less bending. Therefore, coarse wool is often discarded as waste or made into low-cost products. In this work, keratin was extracted from coarse wool by a high-efficiency method, and then, an Ag-doped keratin/PA6 composite nanofiber membrane with enhanced filtration and antibacterial performance was prepared using HCOOH as solvent and reductant. HAADF-STEM (high-angle annular dark field-scanning transmission electron microscopy) shows that AgNPs are uniformly distributed in keratin/PA6 (30/70) nanofibers. TGA (Thermogravimetric Analysis) and DSC (Differential Scanning Calorimetry) were employed to investigate the thermal stability of composite membranes with different keratin and AgNP contents. The present keratin as a dopant with polyamide-6 (PA6) was found not only to improve air filtration efficiency but also to enhance water–vapour transmission (WVT). The addition of the Ag nanoparticles (AgNPs) gave a strong antibacterial activity to the composite membrane against Staphylococcus aureus (99.62%) and Escherichia coli (99.10%). Bacterial filtration efficiency (BFE) of the composite membrane against S. aureus and E. coli were up to 96.8% and 95.6%, respectively. All of the results suggested a great potential for coarse wool extraction and application in the air filtration field.

Photothermal conversion materials have attracted wide attention due to their efficient utilization of light energy. In this study, a (GO)/Bi₂S₃-PVDF/TPU composite nanofiber membrane was systematically developed, comprising GO/Bi₂S₃ nanoparticles (NPs) as a photothermal conversion component and PVDF/TPU composite nanofibers as the substrate. The GO/Bi₂S₃ NPs were synthesized in a one-step way and the PVDF/TPU nanofibers were obtained from a uniformly mixed co-solution by electrospinning. GO nanoparticles with excellent solar harvesting endow the GO/Bi₂S₃-PVDF/TPU membrane with favorable photothermal conversion. In addition, the introduction of Bi₂S₃ NPs further enhances the broadband absorption and photothermal conversion properties of the GO/Bi₂S₃-PVDF/TPU composite membrane due to its perfect broadband absorption performance and coordination with GO. Finally, the results show that the GO/Bi₂S₃-PVDF/TPU composite membrane has the highest light absorption rate (about 95%) in the wavelength range of 400–2500 nm. In the 300 s irradiation process, the temperature changes in the GO/Bi₂S₃-PVDF/TPU composite membrane were the most significant and rapid, and the equilibrium temperature of the same irradiation time was 81 °C. Due to the presence of TPU, the mechanical strength of the composite film was enhanced, which is beneficial for its operational performance. Besides this, the morphology, composition, and thermal property of the membranes were evaluated by corresponding test methods.