Cu2+-induced surface structure transformation on Au nanocubes from a concave to a convex configuration: mechanism and catalytic performance

Abstract

Investigation into the relationship between surface structure and catalytic performance is pivotal for guiding the preparation of high-performance nanocatalysts. However, there is a lack of an effective strategy for fine-tuning the surface structure. In this paper, eight kinds of Au nanocubes (AuNCs) with structures ranging from concave to flat to convex were synthesized using trace amounts of Cu²⁺, and their surface structure-dependent catalytic performance was investigated. In the synthesis, H₂O₂ reduced Au³⁺ to Au⁺ in alkaline CTAB solutions first, and then ascorbic acid was added to initiate the growth of AuNCs. Increasing the Cu²⁺ amounts led to an evolution of concave → flat → convex surfaces, corresponding to transitions of {hk0} facets. The mechanism involves Cu²⁺ catalyzing the reaction between H₂O₂ and ascorbic acid to produce hydroxyl radicals, which promote increased Au⁰ deposition on the surface center. More importantly, the catalytic performance of AuNCs decreases as the surface evolves from concave to flat to convex. This study demonstrates for the first time that the use of simple substances induces concavo-convex transformation of AuNCs, and elucidates the relationship between surface structure and catalytic performance of AuNCs.