Catalytic performance of PdCu supported on mesoporous MCM−41 with different morphologies for reduction of aqueous oxyanion pollutants.

Controlling the size, shape and phase formation of catalyst nanoparticles on support is essential to obtain a superior catalyst for a specific reaction. Herein, the synthesis of palladium–copper (PdCu) bimetallic catalysts supported on mesoporous MCM−41 with different morphologies are reported as well as their catalytic performance for the reduction of oxyanions present in water. X−ray diffraction (XRD) results reveal the formation of disordered face−centred cubic and ordered body−centred cubic phases of intermetallic PdCu for all catalysts. According to the Pd 3d XPS results, the status of the Pd species was dependent on the morphologies of the supports. The rod−like MCM−41 supports could increase the metallic Pd species rather than the spherical−like MCM−41 supports. Transmission electron microscopy (TEM) images show a particle size dependence of PdCu nanoparticles with the morphology of the support. Catalytic test results suggested that the morphology and size affected the PdCu dispersion and, consequently, the catalytic activity for nitrate and bromate reduction. Small and rod-like MCM-41 particles were permitted to obtain a catalyst that achieved a total bromate reduction and a nitrogen selectivity of 61 % in nitrate reduction. These results highlight the importance of the support morphology in reducing the size and minimising the polydispersity of PdCu nanoparticles. [Display omitted] • Bimetallic PdCu catalysts were supported on MCM−41 with different morphologies. • A systematic study identified the most promising catalyst for catalytic reduction of bromate and nitrate. • Dispersion and size of PdCu nanoparticles are strongly dependent on support morphology. • Higher activity to bromate reduction are achieved when small rod-like MCM-41 are used as support. • Migration of Cu (promotor metal) into inner porosity of MCM-41 supports making this metal unavailable for nitrate hydrogenation. [ABSTRACT FROM AUTHOR]