Electrosynthesis of polymer-grade ethylene via acetylene semihydrogenation over undercoordinated Cu nanodots

The removal of acetylene impurities remains important yet challenging to the ethylene downstream industry. Current thermocatalytic semihydrogenation processes require high temperature and excess hydrogen to guarantee complete acetylene conversion. For this reason, renewable electricity-based electrocatalytic semihydrogenation of acetylene over Cu-based catalysts is an attractive route compared to the energy-intensive thermocatalytic processes. However, active Cu electrocatalysts still face competition from side reactions and often require high overpotentials. Here, we present an undercoordinated Cu nanodots catalyst with an onset potential of -0.15 V versus reversible hydrogen electrode that can exclusively convert C2H2 to C2H4 with a maximum Faradaic efficiency of -95.9% and high intrinsic activity in excess of -450 mA cm(-2) under pure C2H2 flow. Subsequently, we successfully demonstrate simulated crude ethylene purification, continuously producing polymer-grade C2H4 with <1 ppm C2H2 for 130 h at a space velocity of 1.35 x 10(5) ml g(cat)(-1) h(-1). Theoretical calculations and in situ spectroscopies reveal a lower energy barrier for acetylene semihydrogenation over undercoordinated Cu sites than nondefective Cu surface, resulting in the excellent C2H2-to-C2H4 catalytic activity of Cu nanodots. Cu-based catalysts for the conversion of C2H2 to C2H4 are plagued by side reactions. Here, Cu nanodots for C2H2 semihydrogenation are reported to reach current densities >400 mA cm(-2) and selectively produce polymer-grade ethylene over 130 h.

Automated summary

The removal of acetylene impurities is important yet challenging to the ethylene downstream industry. Renewable electricity-based electrocatalytic semihydrogenation of acetylene over Cu-based catalysts is an attractive alternative to thermocatalytic processes. However, active Cu electrocatalysts often face competition from side reactions. Here, an undercoordinated Cu nanodots catalyst is reported with excellent C2H2-to-C2H4 catalytic activity.