Study on the NH<sub>3</sub>-SCR performance of CoMnFeAl-LDOs derived from layered double hydroxides supported on CNTs/TiO<sub>2</sub>NWs and its mechanism.

Abstract

In this study, a series of CoMnFeAl layered double oxide (LDO) catalysts supported on multi-walled carbon nanotubes (MWCNTs)/titanium dioxide nanowires (TiO₂NWs) were synthesized via the hydrothermal method. The catalytic performance of the synthesized catalysts was evaluated by activity tests, and their structures and morphologies were characterized using X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), Brunauer-Emmett-Teller (BET) analysis, X-ray photoelectron spectroscopy (XPS), temperature-programmed desorption of ammonia (NH₃-TPD), temperature-programmed desorption of sulfur dioxide (SO₂-TPD), temperature-programmed reduction of hydrogen (H₂-TPR), and <i>in situ</i> diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The results demonstrated that both CoMnFeAl-LDO/CNT and CoMnFeAl-LDO/TiO₂NW catalysts achieved 100% nitrogen oxide (NO) conversion within their optimal temperature ranges and exhibited excellent sulfur resistance. Morphological studies revealed that the introduction of CNTs or TiO₂NWs effectively mitigated the aggregation and stacking of layered double hydroxides (LDHs) during calcination, resulting in enhanced dispersion of active components. Moreover, these modifications increased the surface acidity, redox capability, and SO₂ tolerance of the CoMnFeAl-LDO catalyst. The <i>in situ</i> DRIFTS results indicated that the SCR reactions over CoMnFeAl-LDO/CNT and CoMnFeAl-LDO/TiO₂NW followed both the Eley-Rideal (E-R) and Langmuir-Hinshelwood (L-H) mechanisms. This study highlighted the potential of CNTs/TiO₂NWs to modify CoMnFeAl-LDO catalysts, offering insights for the design of efficient and sulfur-resistant catalysts to address stringent environmental regulations.