Understanding the Role of Coordinatively Unsaturated Al3+Sites on Nanoshaped Al2O3 for Creating Uniform Ni-Cu Alloys for Selective Hydrogenation of Acetylene

In this work, we report a synthesis approach for catalyst preparation using shape-controlled Al2O3 supports with enriched quantities of coordinatively unsaturated Al3+ centers. These centers can then induce ordering in bimetallic catalysts, even with a simple impregnation strategy and this is shown to be beneficial for selective hydrogenation of acetylene. Interestingly, nanorod Al2O3 induced a highly homogeneous and ordered Ni1Cu1 nanoalloy, mainly attributed to the coordination effect of unsaturated Al3+ sites that accelerate atomic diffusion and ordering (affirmed by molecular simulation). The as-obtained Ni-Cu/Al2O3-rod catalyst exhibited both satisfactory activity and ethylene selectivity of 86% under mild reaction conditions, which outperformed most of Nibased catalysts reported to date. Through the combination of in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) studies and computational modeling by density functional theory, it was found that a di-Sigma-adsorption mode of acetylene on the ordered Ni1Cu1 nanoalloy featuring alternating rows of Cu and Ni atoms played a key role in the improvement of selectivity.