Electrospinning Equipment for Research| Coupled electron delocalization and multi-dimensional porosityengineering in TiO, hollow spheres-embedded carbon nanofiber aerogelsfor efficient photocatalytic aniline degradation

Prof. Li Jiansheng at Nanjing University of Science and Technology: Electron Structure and Pore Channel Modulation in TiO₂ Hollow Sphere-Carbon Nanofiber Aerogels for Efficient Photocatalytic Aniline Degradation

The treatment of refractory aromatic organic pollutants in aquatic environments has become a critical challenge in environmental science. Photocatalysis shows great promise by utilizing sunlight to generate reactive oxygen species (ROS), with its core scientific issue being the structure-performance relationship regulation of photocatalytic materials. While a material's intrinsic electronic structure largely determines visible light conversion efficiency, the short lifespan of ROS requires optimized pore structures for rapid pollutant enrichment near active sites, thereby improving ROS utilization and removal rates. However, simultaneously optimizing electronic structures and porosity while exploring their synergies remains challenging.

Recently, Prof. Li Jiansheng's team at Nanjing University of Science and Technology published their findings in Chemical Engineering Journal titled "Coupled electron delocalization and multi-dimensional porosity engineering in TiO₂ hollow spheres-embedded carbon nanofiber aerogels for efficient photocatalytic aniline degradation." The study developed a novel mesoporous TiO₂ hollow sphere-embedded carbon nanofiber aerogel (THS-CNFAs) through electrospinning-freeze drying-pyrolysis, achieving significantly enhanced aniline adsorption (67%) and degradation (96%) under visible light. The 3D porous structure and nitrogen-doped oxygen vacancies synergistically optimized electron delocalization, reduced adsorption energy, and promoted ROS generation. Interconnected channels from PVP/PAN pyrolysis facilitated mass/charge transfer, while defect engineering improved carrier separation. DFT and UPS confirmed electronic structure modulation effectively enhanced photocatalytic activity, providing new insights for fiber-constructed aerogel photocatalysts.

Figure 1: Preparation schematic and microstructure of THS-CNFAs

The THS-CNFAs were fabricated via combined electrospinning-freeze drying-pyrolysis. The material features hierarchical porosity, with uniformly dispersed 700 nm THS maintaining intact hollow morphology within the carbon matrix. HRTEM revealed coexisting anatase (0.35 nm) and brookite (0.29 nm) phases, with EDS confirming elemental homogeneity. This multiscale design synergistically optimized light absorption, mass transfer, and active site exposure.

Figure 2: Structural characterization of THS, CNFAs, and THS-CNFAs

XRD and Raman analyses confirmed the mixed TiO₂ phases, with brookite's higher lattice activity facilitating oxygen vacancy formation. XPS and EPR directly verified Ti-N bonds and oxygen vacancies coexisting. FT-IR showed weakened Ti-O vibrations, reflecting nitrogen-doped lattice reconstruction that balanced mass transfer and active site exposure. These structural features collectively promoted electron delocalization and pollutant enrichment synergies.

Figure 3: Structural optimization and DOS spectra

Density of states analysis revealed N 2p orbitals forming mid-gap states, while oxygen defects acted as electron traps suppressing carrier recombination. Defect engineering optimized band structures through electron density redistribution and Fermi level shifts, achieving synergistic optimization of light absorption, charge separation, and mass transfer - providing new perspectives for high-efficiency photocatalyst development.

Figure 4: Photocatalytic performance and mechanism of THS-CNFAs

THS-CNFAs efficiently degraded aniline via adsorption-photocatalysis synergy. The multidimensional channels of THS and CNFAs significantly enhanced adsorption (67%) and photocatalytic efficiency (96%). Hollow structures improved light harvesting and charge transfer, while CNFAs' π-π stacking promoted aniline adsorption. Quenching tests and EPR confirmed O₂•⁻ and h⁺ as primary active species, with oxygen vacancies and nitrogen doping cooperatively boosting ROS generation (•OH, O₂•⁻, ¹O₂) for efficient degradation.

Figure 5: Aniline molecular structure, Fukui index, and degradation pathways

DFT calculations showed THS-CNFAs had higher aniline adsorption energy than THS alone, with nitrogen doping and oxygen vacancies synergistically enhancing adsorption. LC/MS analysis revealed degradation pathways including nitration, hydroxylation, and polymerization-ring opening reactions. The optimized adsorption-photocatalysis synergy enabled efficient degradation, offering new design principles for 3D carbon nanofiber aerogel photocatalysts.

Paper link: https://www.sciencedirect.com/science/article/abs/pii/S1385894725045243