Investigation of reaction mechanisms of NO with CO on Pd1/MgO and Pd4/MgO catalysts

► The stepwise and concerted mechanisms of NO + CO at Pd1/Pd4/MgO catalyst were theoretically studied. ► The calculated data favour the stepwise mechanism of NO + CO reaction over the concerted mechanism. ► The dissociation of NO for stepwise reaction on Pd1/Pd4/MgO catalyst is the rate-controlling step. ► The rate-controlling step barrier of stepwise reaction at Pd4/MgO catalyst is 57.6 kcal/mol.