Icosahedral metal nanocrystals, with their inherent strain, offer exceptional catalytic properties. However, synthesizing these nanocrystals with high morphological yield remains a significant challenge, limiting the potential of strain engineering for catalyst design. In this study, we introduce a robust oxidative etching and regrowth strategy to synthesize high-yield (~ 90%) icosahedral Au nanocrystals with tunable sizes (12–43 nm). By employing triiodide (I₃⁻) as an oxidative agent, we selectively enrich multiply twinned seeds—the required seed type for icosahedral formation—by removing impurity seeds. Additionally, sulfite ions (SO₃²⁻) selectively cap the Au {111} facet, directing crystal growth toward the desired icosahedral shape. The resulting Au nanocrystals demonstrate strain-enhanced electrocatalytic performance in CO₂ reduction, achieving a Faradaic efficiency of 97.5% for CO production, significantly higher than their non-strained counterparts. This strategy offers a promising pathway for creating well-defined metal nanocrystals, opening new possibilities for both fundamental catalysis research and practical applications.

Sub-100 nm hollow carbon nanospheres with thin shells are highly desirable anode materials for energy storage applications. However, their synthesis remains a great challenge with conventional strategies. In this work, we demonstrate that hollow carbon nanospheres of unprecedentedly small sizes (down to ~32.5 nm and with thickness of ~3.9 nm) can be produced on a large scale by a templating process in a unique reverse micelle system. Reverse micelles enable a spatially confined Stöber process that produces uniform silica nanospheres with significantly reduced sizes compared with those from a conventional Stöber process, and a subsequent well-controlled sol–gel coating process with a resorcinol–formaldehyde resin on these silica nanospheres as a precursor of the hollow carbon nanospheres. Owing to the short diffusion length resulting from their hollow structure, as well as their small size and microporosity, these hollow carbon nanospheres show excellent capacity and cycling stability when used as anode materials for lithium/sodium-ion batteries.