Shape-Controlled Synthesis of 2H Au Nanomaterials for Highly Efficient Carbon Dioxide Reduction Reaction

Colloidal gold (Au) nanomaterials with fine controlled size and shape possess unique physicochemical properties and great potentials in various applications. However, most of the reported Au nanomaterials typically crystallize in the thermodynamically stable face-centered cubic (3C) phase, and there are still great challenges in synthesizing hexagonal close-packed (2H type) Au nanomaterials with high phase purity and controlled size and shape. Here, we report a one-pot colloidal synthesis of free-standing ultrasmall 2H Au nanosheets. A series of 2H Au nanomaterials with controlled shape are then synthesized using the 2H Au nanosheets as seeds. Moreover, the 2H Au nanomaterials exhibit superior electrocatalytic performance toward CO₂ reduction reaction than 3C Au nanoplates, possessing high Faradaic efficiency in a wide applied potential window. Our work provides an effective strategy to design and synthesize Au nanomaterials with unconventional crystal structure and demonstrates the potential of phase engineering in boosting catalytic performances of noble metal nanomaterials.