Monolayer-protected superatomic Au₈Ag₃(PPh₃)₇Br₃ cluster with enhanced electrocatalysis for N₂ reduction

The electrocatalytic nitrogen reduction reaction (ENRR) for ammonia production is widely known to be important but is severely hindered by the high inertness of the NN triple bond and the competitive hydrogen evolution reaction (HER). Here, we report an ENRR study on two monolayer-protected superatom clusters (MPCs), namely, Au₁₃(μ₂-dppm)₆ and Au₈Ag₃(PPh₃)₇Br₃, abbreviated as Au₁₃ and Au₈Ag₃ MPCs, respectively. When supported on graphitic carbon nitride (g-C₃N₄), both catalysts deliver viable ammonia production performance, with the Au₈Ag₃ MPCs exhibiting markedly enhanced ENRR catalysis (an ammonia yield of 5.07 µg h^-1 cm^-2 and a faradaic efficiency of 24.71%), as well as efficient suppression of the HER. The favourable active sites and superior catalysis of the Au₈Ag₃ MPCs are associated with the heteroatom doping and synergistic effect, with a notable superatomic feature pertaining to 8e stability. This work highlights the contribution of delocalized electrons and superatomic orbitals that not only balance the electrons of the metallic cores and tune the d-band centre but also polarize the nitrogen lone pair, leading to MPCs exhibiting enhanced stability and catalysis performance.