π-Adsorption promoted electrocatalytic acetylene semihydrogenation on single-atom Ni dispersed N-doped carbon

In pursuit of environmental friendliness and high economic efficiency, renewable energy-driven selective acetylene semihydrogenation under ambient conditions is urgently required but remains a grand challenge. Herein, we explore single-atom nickel (Ni) dispersed N-doped carbon (SA-Ni-NC) as a novel electrocatalyst for catalyzing selective acetylene semihydrogenation. In situ electrochemical Raman and theoretical investigations reveal that weak π-adsorption of ethylene on individual Ni sites in SA-Ni-NC facilitates its desorption and thus avoids its overhydrogenation. Eventually, under pure acetylene flow, SA-Ni-NC exhibits a high ethylene faradaic efficiency (FEethylene) of 91.3% and a large current density of −92.2 mA cm−2 at −0.6 V vs. the reversible hydrogen electrode (RHE). Even in crude ethylene stream containing 1% acetylene impurities (1 × 104 ppm), SA-Ni-NC still manifests a high acetylene conversion of 97.4% with a large space velocity (SV) of 2.4 × 104 mL gcat−1 h−1 and a high turnover frequency (TOF) of 22.9 h−1 for each Ni atom.