NO selective reduction by hydrogen over bimetallic Pd–Ir/TiO2 catalyst

TiO2 supported monometallic and bimetallic catalysts were prepared and employed in the selective catalytic reduction of nitrogen oxides by hydrogen (H2-SCR). Bimetallic Pd–Ir/TiO2 exhibited high activity in H2-SCR reaction and NOx conversion of > 80%, with N2 selectivity > 80%, could be obtained in the temperature range of 413–473 K. The existence states of supported metals before and after H2-SCR were investigated by X-ray photoelectron spectroscopy, and the surface species formed during H2-SCR reaction were monitored by in situ FTIR spectroscopy. Based on the catalytic and characterization results, the synergistic effects between Pd and Ir were discussed and the H2-SCR reaction pathways over Pd–Ir/TiO2 were proposed.

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► The synergistic effects between Pd and Ir in Pd-Ir/TiO2 lead to high H2-SCR activity.
► The presence of Pd suppresses the oxidation of Ir during reaction.
► Hydrogen on Pd sites promotes the removal of oxygen on Ir sites through spillover.