Understanding the\nRole of Coordinatively Unsaturated\nAl<sup>3+</sup> Sites on Nanoshaped Al<sub>2</sub>O<sub>3</sub> for\nCreating Uniform Ni–Cu Alloys for Selective Hydrogenation of\nAcetylene

In\nthis work, we report a synthesis approach for catalyst\npreparation\nusing shape-controlled Al<sub>2</sub>O<sub>3</sub> supports with enriched\nquantities of coordinatively unsaturated Al<sup>3+</sup> centers.\nThese centers can then induce ordering in bimetallic catalysts, even\nwith a simple impregnation strategy and this is shown to be beneficial\nfor selective hydrogenation of acetylene. Interestingly, nanorod Al<sub>2</sub>O<sub>3</sub> induced a highly homogeneous and ordered Ni<sub>1</sub>Cu<sub>1</sub> nanoalloy, mainly attributed to the coordination\neffect of unsaturated Al<sup>3+</sup> sites that accelerate atomic\ndiffusion and ordering (affirmed by molecular simulation). The as-obtained\nNi–Cu/Al<sub>2</sub>O<sub>3</sub>-rod catalyst exhibited both\nsatisfactory activity and ethylene selectivity of 86% under mild reaction\nconditions, which outperformed most of Ni-based catalysts reported\nto date. Through the combination of in situ diffuse reflectance infrared\nFourier transform spectroscopy (DRIFTS) studies and computational\nmodeling by density functional theory, it was found that a di-σ-adsorption\nmode of acetylene on the ordered Ni<sub>1</sub>Cu<sub>1</sub> nanoalloy\nfeaturing alternating rows of Cu and Ni atoms played a key role in\nthe improvement of selectivity.