Facet-defined single-crystalline nanocrystals <i>via</i> solution synthesis for electrocatalysis

Electrocatalysis is fundamental to advancing clean energy technologies such as fuel cells, water electrolyzers, and carbon dioxide conversion systems. The efficiency of these technologies hinges on the rational design of electrocatalysts, which has long been hindered by the structural complexity of conventional nanomaterials. Over the past decade, facet-defined single-crystalline nanocrystals (SCNCs) have emerged as a powerful platform to bridge the gap between ideal single-crystal surface science and practical catalysis. By offering well-defined and tunable surface atomic arrangements, these nanocrystals enable the establishment of clear structure-activity relationships, allowing direct evaluation of surface dynamics and activity under operating conditions. This review summarizes recent advances in the synthesis, characterization, and application of facet-defined SCNCs, highlights their unique role in elucidating structure-performance relationships, and discusses the challenges and opportunities for translating these model catalysts into practical energy conversion technologies.