Fully Exposed Nickel\nClusters for Semihydrogenation\nof Acetylene

Semihydrogenation\nof acetylene to ethylene is a key process\nfor\nethylene purification in the chemical industry. The pursuit of an\neffective non-noble metal acetylene selective hydrogenation catalyst\nwith low cost, high efficiency, and ultrastability is extremely urgent,\nespecially for industrial applications. However, achieving high ethylene\nselectivity at full conversion under a low reaction temperature remains\nchallenging due to the imbalance of the H<sub>2</sub> splitting ability\nand intermediate (ethylene) hydrogenation. Herein, we designed atomically\ndispersed and fully exposed Ni clusters on a nanodiamond@graphene\nsupport. H<sub>2</sub>–D<sub>2</sub> exchange experiments and\ndensity functional theory calculations reveal that acetylene and hydrogen\ncan be efficiently activated on fully exposed Ni cluster sites due\nto the enhanced catalytic hydrogenation catalytic ability. Furthermore,\nthe desorption of ethylene on fully exposed Ni cluster sites is much\nmore favored compared to further dissociation of H<sub>2</sub>, leading\nto the high selectivity of ethylene. Thereby, the fully exposed Ni\ncluster catalyst delivered an ethylene selectivity of 85% at full\nconversion for semihydrogenation of acetylene at 190 °C with\na specific activity of 667 mL<sub>C2H2</sub>·g<sub>Ni</sub><sup>–1</sup>·min<sup>–1</sup>, exceeding the catalytic\nefficiency of most supported Ni catalysts. The implementation of the\nfully exposed Ni cluster catalyst provides an effective strategy for\nimproving the catalytic efficiency of non-noble metal acetylene selective\nhydrogenation catalysts while obtaining high ethylene selectivity.\nThe precise regulation of metal active sites at the subnanometer scale\nhas a significant effect on the rational design of high catalytic\nperformance atomically dispersed non-noble metal catalysts.