Ligand-Mediated Activity of Cu₄ Clusters Boosts Electrocatalytic Nitrate Reduction

Surface ligands play a crucial role in modifying catalytic environments and enhancing performance through various mechanisms. However, the multivariate synergistic mechanisms, dynamic evolution patterns, and universal design principles of ligand effects remain to be thoroughly investigated. Metal clusters, with their atomically precise structures, serve as ideal models for studying ligand regulation mechanisms. Herein, we synthesized two copper clusters of N,S-bidentate ligand-protected Cu₄(PTI)₄ and Cu₄(BTT)₄ featuring identical metallic core structures but distinct ligand architectures and evaluated their catalytic performance for the nitrate reduction reaction (NO₃RR). Notably, the Cu₄(PTI)₄ cluster with stronger electron-withdrawing ligands achieved near-100% Faradaic efficiency at optimal potentials, significantly surpassing the Cu₄(BTT)₄. Through in situ characterization and theoretical calculations, we unveiled that enhancing the electron-withdrawing capability of ligands induces alterations in the local microenvironment and electronic structure of metal active sites, thereby exerting positive impacts on electrocatalytic NO₃RR performance.