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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