In situ design of Cu and Co nanoparticles encapsulated in N-doped graphene with core–shell structure-derived 8-hydroxyquinoline complexes for the selective catalytic reduction of NOx by NH3

Abstract

The selective catalytic reduction of NO_x with NH₃ (NH₃-SCR) is an attractive technology for the abatement of NO_x emission. Novel core–shell structure catalysts with Cu and Co nanoparticles surrounding by N-doped graphene (Cu@N-Gr and Co@N-Gr) were achieved using a simple direct annealing method of copper acetate, cobalt acetate and 8-hydroxyquinoline complexes and then applied for NH₃-SCR. The Cu@N-Gr and Co@N-Gr catalysts exhibited better NO_x conversion than pure Cu and Co nanoparticle modified conventional carbon materials in NH₃-SCR across a wide temperature window (200–350 °C), which is because graphene shells can effectively prevent the aggregation of Cu and Co nanoparticles, thereby there are highly dispersed active sites on graphene. In addition, Cu@N-Gr and Co@N-Gr showed excellent SO₂ resistance for a duration of 10 h at a high temperature due to the decomposition of ammonium bisulfate. However, this was not the case at low temperature because of the formation of ammonium bisulfate on the catalyst surface that blocked the active sites. This work lays the foundations for further industrialization applications of denitrification catalysts.