Bimetallic modification of MnFeO_x nanobelts with Nb and Nd for enhanced low-temperature de-NO_x performance and SO₂ tolerance

Nitrogen oxide (NO_x) is one of the key factors contributing to air pollution, and selective catalytic reduction with ammonia (NH₃-SCR) is widely used for denitrification (de-NO_x). To effectively deal with the NO_x pollution, it is urgent to develop efficient catalyst working at below 300 °C with a wide operating temperature window. Herein, a series of ferromanganese oxides (MnFeO_x) nanobelts are bimetallically modified with niobium (Nb) and neodymium (Nd) for the first time via electrospinning method. The resultant MnFeNbNdO_x catalysts present improved low-temperature de-NO_x performance and sulfur dioxide (SO₂) tolerance, particularly MnFeNb_0.2Nd_0.1O_x who achieves a NO_x conversion up to over 90 % during the range of 120–330 °C and an enhanced tolerance of water (H₂O) and SO₂. Experimental and theoretical calculations confirm that strong adsorption of nitric oxide (NO) and ammonia (NH₃) and weak adsorption of SO₂ with the synergy of Nd, Nb and Mn enable MnFeNb_0.2Nd_0.1O_x excellent SCR activity and good SO₂ tolerance. In-situ diffuse reflectance infrared Fourier transform spectra (DRIFTS) further reveal that the de-NO_x reaction over MnFeNb_0.2Nd_0.1O_x follows both Eley-Rideal (E-R) and Langmuir-Hinshel-wood (L-H) mechanisms. This study will inspire the further design and study of the synergy of transition metals and rare earth elements for de-NO_x.