N8 stabilized single-atom Pd for highly selective hydrogenation of acetylene

• N 8 stabilized single-atom Pd catalyst was synthesized with cyclic voltammetry. • Single-atom Pd is stabilized by attaching to the end N of N 8. • H 2 dissociates on the N atom (next to Pd) instead of conventionally on Pd. • Pd 1 -N 8 /CNT showed superior performance for acetylene hydrogenaton at 40 °C. Single-atom catalysts show a promising future in many reactions even though great challenges still remain such as facile synthesis and long stability. In this work, a single-atom Pd catalyst attached to a designed N 8 Lewis base species (Pd 1 -N 8 /CNT) is synthesized with cyclic voltammetry (CV) method. The catalyst demonstrates long stability and enhanced C 2 H 4 selectivity in selective hydrogenation of acetylene at 40 °C. CV is carried out in a three-electrode setup with PdO/CNT as the working electrode in NaN 3 solution. HAADF-STEM confirms single-atom Pd sites are successfully isolated. XPS measurements and Bader charge calculations indicate N 8 is effectively synthesized on CNT substrate after CV treatment while single-atom Pd is stabilized by attaching to the end N of N 8 . Acetylene-temperature programed desorption (C 2 H 2 -TPD) and density functional theory (DFT) calculations suggest C 2 H 2 favors the π bonding on single Pd atom, while H 2 dissociates on the N atom (next to Pd) instead of conventionally on Pd. The synergistic effect favors C 2 H 4 formation but prevents full hydrogenation of acetylene to C 2 H 6 . This work opens up a new perspective to design and synthesize more selective catalysts with isolated single-atom sites.