Rapid synthesis of concave gold nanocubes with tunable indentations and high index facets for enhanced catalytic performance

Precise control of morphology is crucial for achieving sophisticated properties and advanced applications of nanomaterials. Among different shapes, concave nanomaterials have emerged as a novel class of unconventional materials with superior properties in comparison to their convex counterparts, owing to abundant atomic steps and kinks. Here, we report rapid (10 min) one-pot synthesis of concave gold nanocubes (CGNs) with tunable indentations and high-index facets, using a combination of ascorbic acid (AA) and H2O2. The synthesis of CGNs involved the reduction of Au3+ to Au+ by H2O2 under alkaline conditions, followed by initiating CGN formation upon the addition of AA. Cyclic voltammetry scanning confirmed that AA and H2O2 co-participate in the reduction of Au+. The concentrations of H2O2 and AA were precisely controlled to adjust the indentation and high-index facets, such as {7 3 0}, {6 1 0}, {3 1 0}, {8 3 0}, etc. The concave structures of CGNs were formed due to Au0 deposition on {1 1 1} facets at the tips for AA and {1 0 0} facets at the surface center for H2O2. Remarkably, the typical CGNs with {7 3 0} facets exhibited higher catalytic activity towards the reduction of nitrophenol by NaBH4 than many other Au nanomaterials, with an unusual kinetic profile, i.e., an increasing reaction rate.