CO₂ Reduction on Copper’s Twin Boundary

Electrocatalysts are evolving toward chemically tunable atomic structures, among which the catalyst engineering from a defect perspective represents one of the mainstream technical genres. However, most defects cannot be purified or their numbers gauged, making them too complex to explore the hidden catalytic mechanism. A twin boundary, with well-defined symmetric structure and high electrocatalytic activity, is an elegant one-dimensional model catalyst in pursuing such studies. Here on polished Cu electrodes, we successfully synthesized a series of copper twin boundaries, whose density ranges from 0 to 105 cm–1. The CH4 turnover frequency on the twin boundary atoms is 3 orders higher than that on the plane atoms, and the local partial current density reaches 1294 mA cm–2, with an intrinsic Faradaic efficiency of 92%. An intermediate experiment and density functional theory studies confirm the twin boundary’s advantage in converting the absorbed CO* into CH4.