Nitrate hydrogenation on Pd–Cu/TiO2 catalyst prepared by photo-deposition

Bimetallic Pd–Cu/TiO2 is prepared by successive photo-deposition process and characterized by means of TEM, H2-TPR and FTIR spectra of CO adsorption. The as-prepared Pd–Cu/TiO2 is studied as promising catalyst for nitrate hydrogenation and a step-wise reaction process, divided into nitrate hydrogenation to nitrite and nitrite hydrogenation to nitrogen, is observed. The active sites for nitrate and nitrite hydrogenation over Pd–Cu/TiO2 are discussed individually. It is observed that basic conditions of reaction solution favor the hydrogenation of nitrate to nitrite, while acidic conditions favor the hydrogenation of nitrite to nitrogen. For nitrite hydrogenation, acetic acid is more efficient acidic buffer than hydrochloric acid due to an in situ buffering effect. Based on these results, a two-step process, by changing the reaction solution from basic conditions to acidic conditions at midterm, is developed to realize the hydrogenation of nitrate to nitrogen over bimetallic Pd–Cu/TiO2.

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► Bimetallic Pd–Cu/TiO2, with typical structure of Cu@Pd@TiO2, is prepared by successive photo-deposition.
► A step-wise reaction process, including nitrate hydrogenation to nitrite and nitrite hydrogenation to nitrogen, is observed.
► A two-step process, by changing the reaction solution from basic conditions to acid conditions at midterm, is developed for nitrate hydrogenation to nitrogen.