Two-Dimensional Silver Cyanamide Nanocrystals toward CO2 Reduction

Metal cyanamides have an organic-inorganic hybrid structure similar to MOFs, which are expected to possess interesting catalytic properties. However, the structural complexity of these compounds sets up a big barrier to realize shape manipulation and further understanding on the structure-activity relationship. Here, we describe seed-mediated colloidal synthesis as a facile approach to obtain Ag2NCN near-monodisperse nanocrystals (NCs: nanorods, nanowires, and nanosheets) and their related CO2 catalytic activity. The control experiment unveiled the prominent role of the anisotropy for quasi-linear [NCN](2-) anions in obtaining the desired growth order of different crystal planes. The formic acid production of nearly 20% Faradaic efficiency is observed when the as-prepared Ag2NCN NCs were tested for electrocatalytic CO2 reduction reactions. The exposed (200) planes exhibit evident higher catalytic activity compared to other planes, showing morphology-dependent activity. Our result reveals that the anisotropic structure of ions leads to their preferential growth of the NCs and thus may have greater implications for the shape-controlled synthesis of complex ions containing compounds and their related catalytic activity.