Metal phthalocyanines as efficient electrocatalysts for acetylene semihydrogenation

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• Cobalt phthalocyanine was developed as an electrocatalyst for acetylene semihydrogenation. • Cobalt phthalocyanine exhibited an ethylene current density of 150.8 mA cm −2 and a FE of ∼96%. • Co sites in cobalt phthalocyanine facilitate acetylene adsorption and ethylene desorption. • Under ethylene-rich flow, CoPc manifested a high conversion rate, TOF and space velocity. Compared to their booming thermocatalytic counterparts, electrocatalytic acetylene semihydrogenation still remain stagnant owing to its low activity and poor selectivity. Here, we first explore metal phthalocyanines (M(Pc)s) featuring a defined metal coordination environment as electrocatalysts for acetylene semihydrogenation. Consequently, CoPc exhibits an ethylene current density of 150.8 mA cm −2 and a ∼ 96% ethylene faradaic efficiency under a pure acetylene stream. In-situ electrochemical Raman and theoretical calculations demonstrate that CoPc favors acetylene absorption/hydrogenation processes. Even for crude ethylene containing 1 × 10 4 ppm acetylene, CoPc manifests a ∼ 99.5% acetylene conversion, a high turnover frequency of 4.86 × 10 –3 s −1 and a large space velocity of 2.4 × 10 5 ml·g cat –1 ·h −1 , outperforming those for reported thermocatalysts. This work facilitates the development of electrocatalytic acetylene semihydrogenation and promises alternatives to traditional thermocatalytic processes.