Bimetallic Ni-Cu alloy nanoparticles supported on silica for the water-gas shift reaction: activating surface hydroxyls via enhanced CO adsorption

Highly dispersed Ni-Cu nanoparticles supported on SiO2 were synthesized via an in situ self-assembly core-shell precursor route. Monometallic (Ni and Cu) and bimetallic (Ni-Cu) catalysts were synthesized, characterized by XRD, H-2-TPR, XAS, XPS, CO-TPR, DRIFTS and N-2 adsorption analysis and tested for the water-gas shift reaction. Formation of a highly dispersed Ni-Cu alloy was confirmed via XRD, H-2-TPR, XAS and DRIFTS. Oleic acid was found to promote the dispersion of both monometallic and bimetallic particles, anchoring small metal particles to the support via enhanced metal-support interactions. The DRIFTS results suggest that CO is adsorbed on the Cu sites in the Ni-Cu alloy thereby suppressing methanation. Additionally, stronger CO adsorption on the 5Ni5Cu/SiO2 (OA) catalyst activates the surface terminal hydroxyl groups on silica for enhanced CO conversion. The promotional effect of OA on the WGS activity was evidenced through kinetic measurements: the 5Ni5Cu/SiO2 (OA) catalyst obtained a turnover frequency of 0.004 s(-1) which is twice that of the 5Ni5Cu/SiO2 catalyst (0.002 s(-1)).