Exposure of Active Metal Sites on Cu ₁₄ Nanoclusters for Highly Selective Electrocatalytic Nitrate Reduction

Atomically precise metal nanoclusters (NCs) have been extensively used as catalysts for various reactions owing to the ultimate controllability of their parameters, such as number of constituent atoms, crystal structure, and alloying characteristics. However, for many metal NCs, their surfaces are entirely covered by ligands, preventing the exposure of surface metal atoms that serve as active sites and thus hindering their catalytic functionality. Herein, we report that the exposure of metal sites in Cu14 NC can be achieved by a facile modification of the thiolate ligands. Consequently, we found that Cu14 NC with an exposed Cu site exhibits significantly higher ammonia selectivity and production rate in electrochemical nitrate reduction. These findings underscore the importance of atomically precise control for metal NCs, not only of their overall geometric structures but also of their reactive sites, for achieving highly selective and active catalysts, contributing to the future design of diverse metal NC catalysts.