Pd–Cu bimetallic catalysts supported on TiO2–CeO2 mixed oxides for aqueous nitrate reduction by hydrogen

• Pd–Cu/TiO2–CeO2 catalysts were tested for catalytic reduction of nitrate.
• The chemical state of surface changed with the amount of ceria.
• The catalyst with small amount of ceria exhibited most reduced states.
• The reduced states of catalyst were beneficial to the nitrate reduction.

Pd–Cu supported on TiO2–CeO2 mixed oxides (Pd–Cu/TiO2–CeO2) were tested for the reduction of nitrate ions in water. Compared with a Pd–Cu catalyst with TiO2 only as support (Pd–Cu/TiO2), which was proved to be active for this reaction in our previous study, Pd–Cu/TiO2–CeO2 showed improved activity if TiO2–CeO2 contained an appropriate amount of ceria (Ti:Ce = 18:1). Especially, the Pd–Cu/TiO2–CeO2 (Ti:Ce = 18:1) showed the initial nitrate reduction rate of 3.20 mmol/min/gcat, eight times higher than that of Pd–Cu/TiO2 (0.41 mmol/min/gcat). It was supposed that the improved activity of the catalyst was attributable to the reduced surface (oxygen vacancies) of the support and zero-valence states of the active metals (including the Pd–Cu alloy) in the catalyst.

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