Oxidative etching and regrowth strategy enables high-yield synthesis of icosahedral gold nanocrystals for efficient CO₂ reduction

Icosahedral metal nanocrystals are known for their superior catalytic properties, driven by unique structural features and intrinsic tensile strain. These nanocrystals are composed of twenty {111} facets and thirty five-fold twin boundaries, generating substantial strain that enhances the adsorption and activation of reactant molecules. While established synthetic protocols exist for icosahedral nanocrystals of metals such as Pd, Pt, and Ru, achieving high-yield, precisely controlled synthesis of icosahedral Au nanocrystals has remained a considerable challenge. Gold, due to its relatively weak binding strength to guest molecules, is expected to provide moderate adsorption energy for guest molecules by forming an icosahedral morphology, holding great potential in CO-involved catalytic reactions (e.g., electrochemical CO2 reduction).

In a recent study published in Nano Research, a team led by Prof. Chuanbo Gao (Xi’an Jiaotong University) and Prof. Tao Cheng (Soochow University) reported a robust oxidative etching and regrowth strategy for the size-controlled, high-yield synthesis of icosahedral Au nanocrystals. This approach produces uniform nanocrystals with sizes ranging from 12 to 43 nm and an impressive yield of ~90%.

The success of this strategy hinges on two key design elements: (1) Triiodide (I₃^–) is introduced as an oxidizing agent, which selectively etches non-twinned impurity seeds while preserving five-fold twinned seeds that promote icosahedral growth. This selective etching mechanism significantly enhances the purity and yield of the icosahedral product. (2) Sulfite ions (SO₃^2–) are introduced as facet-selective ligands, preferentially adsorbing on Au{111} planes. This guides the crystal growth along specific orientations, facilitating the formation of the desired icosahedral structure. Transmission electron microscopy (TEM) confirmed the high morphological purity of the nanocrystals, with the 12 nm sample achieving up to 90% icosahedral yield. Bismuth ion stripping voltammetry further validated the dominance of exposed {111} facets, consistent with the targeted structure.

In electrocatalytic tests, these icosahedral Au nanocrystals demonstrated significantly enhanced performance in the CO₂RR. Compared to non-strained spherical Au nanocrystals, the strained icosahedral nanocrystals delivered higher CO₂ reduction current densities. The 26.4 nm sample, in particular, achieved a Faradaic efficiency of 97.5% for CO production at a current density of 50 mA cm^–2, outperforming many previously reported catalysts. The nanocrystals also showed excellent long-term stability, maintaining over 97% CO selectivity during 17 hours of continuous operation, with no significant morphological or structural degradation.

To understand the underlying mechanisms, the team conducted density functional theory (DFT) calculations, which confirmed that the moderate tensile strain present in icosahedral nanocrystals enhances the adsorption of key reaction intermediates and lowers the energy barrier for CO₂ activation and conversion. Excessive strain was found to hinder CO desorption, negatively affecting reaction kinetics—explaining why the 26.4 nm nanocrystals with optimal strain offered the best performance.

This work provides valuable insights into the shape-controlled synthesis of noble metal nanocrystals and paves the way for advanced applications in plasmonic catalysis, CO₂  conversion, and sustainable energy technologies.

Acknowledgments:

C.G. acknowledges support from the National Natural Science Foundation of China (22371222), the Science Fund for Distinguished Young Scholars of Shaanxi Province (2024JC-JCQN-14), and the Fundamental Research Fund for Central Universities. T.C. acknowledges support from the National Natural Science Foundation of China (22173066 and 22103054) and the Natural Science Foundation of Jiangsu Higher Education Institutions (BK20230065).

About Nano Research

Nano Research is a peer-reviewed, open access, international and interdisciplinary research journal, sponsored by Tsinghua University and the Chinese Chemical Society, published by Tsinghua University Press on the platform SciOpen. It publishes original high-quality research and significant review articles on all aspects of nanoscience and nanotechnology, ranging from basic aspects of the science of nanoscale materials to practical applications of such materials. After 18 years of development, it has become one of the most influential academic journals in the nano field. Nano Research has published more than 1,000 papers every year from 2022, with its cumulative count surpassing 7,000 articles. In 2024 InCites Journal Citation Reports, its 2024 IF is 9.0 (8.7, 5 years), and it continues to be the Q1 area among the four subject classifications. Nano Research Award, established by Nano Research together with TUP and Springer Nature in 2013, and Nano Research Young Innovators (NR45) Awards, established by Nano Research in 2018, have become international academic awards with global influence.