Synthesis of Pt/K2CO3/MgAlOx–reduced graphene oxide hybrids as promising NOx storage–reduction catalysts with superior catalytic performance

Pt/K2CO3/MgAlOx-reduced graphene oxide (Pt/K/MgAlOx-rGO) hybrids were synthesized, characterized and tested as a promising NOx storage and reduction (NSR) catalyst. Mg-Al layered double hydroxides (LDHs) were grown on rGO via in situ hydrothermal crystallization. The structure and morphology of samples were thoroughly characterized using various techniques. Isothermal NOx adsorption tests indicated that MgAlOx-rGO hybrid exhibited better NOx trapping performance than MgAlOx, from 0.44 to 0.61 mmol · g-1, which can be attributed to the enhanced particle dispersion and stabilization. In addition, a series of MgAlOx-rGO loaded with 2 wt% Pt and different loadings (5, 10, 15, and 20 wt%) of K2CO3 (denoted as Pt/K/MgAlOx-rGO) were obtained by sequential impregnation. The influence of 5% H2O on the NOx storage capacity of MgAlOx-rGO loaded with 2 wt% Pt and 10% K2CO3 (2Pt/10 K/MgAlOx-rGO) catalyst was also evaluated. In all, the 2Pt/10 K/MgAlOx-rGO catalyst not only exhibited high thermal stability and NOx storage capacity of 1.12 mmol · g-1, but also possessed excellent H2O resistance and lean-rich cycling performance, with an overall 78.4% of NOx removal. This work provided a new scheme for the preparation of highly dispersed MgAlOx-rGO hybrid based NSR catalysts.