Stepwise structural evolution toward robust carboranealkynyl-protected copper nanocluster catalysts for nitrate electroreduction.

Atomically precise metal nanoclusters (NCs) are emerging as idealized model catalysts for imprecise metal nanoparticles to unveil their structure-activity relationship. However, the directional synthesis of robust metal NCs with accessible catalytic active sites remains a great challenge. In this work, we achieved bulky carboranealkynyl-protected copper NCs, the monomer ·3PF and -carboranealkynyl bridged dimer ·4PF, with fair stability as well as accessible open metal sites step by step through external ligand shell modification and metal-core evolution. Both ·3PF and ·4PF demonstrate remarkable catalytic activity and selectivity in electrocatalytic nitrate (NO-) reduction to NH reaction, with the dimer ·4PF displaying superior performance. The mechanism of this catalytic reaction was elucidated through theoretical computations in conjunction with in situ FTIR spectra. This study not only provides strategies for accessing desired copper NC catalysts but also establishes a platform to uncover the structure-activity relationship of copper NCs.