Investigation of the synergistic effect of O2/H2O pretreatment and Na addition on the NO-semichar reaction

The surface physicochemical features of semichar play a crucial role in determining its reactivity, dominating the subsequent reaction between semichar and NO. Therefore, the synergistic effect of O2/H2O pretreatment and Na addition on the microstructural characteristics of semichar and NO reduction characteristics is revealed through experimental and density functional theory (DFT) methods. Experimental results indicate that O2/H2O pre treatments with Na addition promote the development of pores. Micropores are considered the major pore structures in semichar. Based on Raman and laser-induced breakdown spectroscopy (LIBS) results, the combined effect of O2/H2O pretreatments and Na promotes the formation of small aromatic rings, exhibiting a positive correlation with molecular emissions. Temperature-programmed reduction experiments (TPR) demonstrate that the inclusion of Na in O2/H2O pretreatments enhances the reduction ability of NO. The reduction mechanism of NO-semichar is determined using the DFT method. The simulation results indicate that the adsorption of H2O during O2/H2O pretreatment is chemisorption and independent of Na atom. The additional Na reduces the energy gap of the NO-semichar, facilitating the decomposition of N2 by weakening the conjugated components of the aromatic structures.