Design of platinum group metal-free automotive three-way catalyst: MgMn2O4 and CuCo2O4 in tandem layout

Platinum group metal (PGM)-free and Cr-free automotive three-way catalyst (TWC) was examined using two types of base-metal oxides for hydrocarbon preferential oxidation (HC-PROX) and NO reduction by CO in tandem configuration. MnOx-based binary mixed metal oxides (X1Mn2, X = Ba, Ca, Co, Cu, Fe, Mg, Ni, Zn, Zr) were investigated for the design of HC-PROX catalysts. Mg1Mn2 achieved both high propene oxidation activity and low CO oxidation activity, and the catalyst phase was determined as MgMn 2 O 4 having the spinel structure. A tandem TWC composed of MgMn 2 O 4 for HC-PROX and CuCo 2 O 4 for NO-CO reaction showed comparable NO reduction activity and higher oxidation activity of propene and CO compared to Rh/ZrO 2 as a benchmark. In-situ FTIR study clarified that the suppression of CO oxidation over MgMn 2 O 4 is caused by strongly adsorbed acetate and formate on the catalyst surface. • MgMn 2 O 4 shows high activity and selectivity for hydrocarbon preferential oxidation. • Strong adsorption of acetate and formate suppresses CO oxidation. • High TWC activity was obtained using MgMn 2 O 4 + CuCo 2 O 4 tandem catalyst. • A PGM-free and Cr-free tandem TWC was proposed.