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[Display omitted] • The Al 2 O 3 supported carbon coated NiCuCo alloy were prepared via a simple method. • The trade-off between activity and selectivity was overcome on NiCuCo@C/Al 2 O 3. • The electron-rich Ni species weaken the desorption of acetylene and ethylene. • The reduced formation of green oil results in excellent stability. Achieving high ethylene selectivity and activity simultaneously for acetylene selective hydrogenation still remains challenging. Here, the challenge of the trade-off between activity and selectivity was solved by synergizing electronic effects and spatial confinement, which was achieved by confining the Ni-Co-Cu trimetallic nanoparticles in a carbon layer (Ni x Cu y Co z @C/Al 2 O 3). Compared to the catalyst without carbon encapsulation (Ni x Cu y Co z /Al 2 O 3), Ni x Cu y Co z @C/Al 2 O 3 showed superior catalytic performance in terms of enhanced activity, selectivity and stability. Under optimal conditions, acetylene conversion of 100% and ethylene selectivity of 89% were achieved, whereas Ni x Cu y Co z /Al 2 O 3 exhibited lower acetylene conversion (92%) and ethylene selectivity (21%). Detailed characterizations reveal that the electronic structure can be regulated flexibly by controlling the composition of Ni-Co-Cu nanoparticles. The enhanced activity and selectivity were attributed to the weakened adsorption of acetylene and ethylene on the electron-rich Ni. The improved stability was related to the carbon layer, which suppressed the acetylene coupling by the acidic sites on the Al 2 O 3 surface. [ABSTRACT FROM AUTHOR]

[Display omitted] • Carbon confined Cu-Pd nanoalloy catalysts are successfully synthesized through an eco-friendly, facile and efficient approach. • Carbon encapsulation strategy efficiently improves the ethylene selectivity and stability for selective hydrogenation of acetylene. • Carbon layer acts as "cages" for confining the growth of the carbon chain to oligomer during the acetylene hydrogenation. • This synthesis strategy can be extended to other carbon confined Cu and Ag-based bimetal catalysts. A catalyst with high selectivity for acetylene selective hydrogenation is highly desirable, yet ideal selectivity often comes at the price of activity loss. Here, a carbon confined Cu 15 Pd catalyst (Cu 15 Pd@C) was fabricated through an eco-friendly and efficient approach, which improves ethylene selectivity while at the same time, maintains high activity. Under optimized conditions, acetylene conversion of 100% and ethylene selectivity of 91% were simultaneously achieved. Comprehensive characterization and DFT reveal that the carbon layer not only promotes the formation of smaller nanoparticles, but effectively inhibits the production of green oil, which is associated to the confined spatial microenvironment by the carbon layer, posing steric hindrance to chain growth from acetylene coupling. A series of carbon confined Cu and Ag-based bimetal catalysts were fabricated through the same method, proving the facilitation of carbon layer on such selective hydrogenation universal, and also showed great potential of our method and catalysts in practical application. [ABSTRACT FROM AUTHOR]