Effect of supports on Pd–Cu bimetallic catalysts for nitrate and nitrite reduction in water

The activities of the Pd–Cu catalysts supported on various metal oxides for the reduction of nitrate and nitrite ions were compared at a constant pH. Among them, the catalysts supported on titania xerogel prepared by a glycothermal method showed the highest performance for nitrate reduction. For the reduction of nitrite ions, Pd–Cu/CeO2 showed the highest catalytic activity; however, significant dissolution of the components of the catalyst was observed during the reaction at a relatively low pH range. On the other hand, a single-component Pd catalyst supported on titania xerogel showed excellent activity for the reduction of nitrite ion and could be used at a wide range of pH. For these catalysts, the product selectivity for N2 from nitrite ions was markedly improved by decreasing the partial pressure of H2 in the feed.

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► Activities of metal oxide-supported Pd–Cu catalysts were compared at constant pH.
► Titania xerogels prepared by the glycothermal method are excellent catalyst supports.
► Titania xerogel markedly promotes the reduction of surface Cu species.
► Severe dissolution of ceria-supported catalysts was observed at low pH.