A precursor-valence-gating strategy for controllable synthesis of metal nanocrystal catalysts with varied periodicities

Transition-metal nanocrystal (TMN) catalysts are essential for energy conversion and storage, but their facile and controllable synthesis remains challenging. Here we report a general precursor-valence-gating strategy to prepare various monocrystalline and polycrystalline TMNs (MC/PC-TMNs, M = Co, Ni or Cu). Unlike complex regulation of traditional experimental parameters, we discover that the solid-state precursor’s oxidation state—an intrinsic parameter—governs the nucleation rate and ultimately dictates atomic crystallization periodicity. Consequently, the controllable preparation of MC/PC-TMNs was readily achieved through designing the valence diversity of the corresponding precursors. Furthermore, taking MC/PC-Co catalysts as examples, we investigate the correlation between atomic arrangements and catalytic dynamics and reveal that the PC-Co catalyst with the lower-coordination environment, compared with MC-Co, substantially promotes the conversion of reaction intermediates in the hydrazine oxidation reaction. As a result, PC-Co exhibits an ultralow Tafel slope of 14 mV dec −1 , and an assembled hydrazine oxidation reaction-based battery demonstrates excellent stability for 1,200 h at 10 mA cm −2 . This work paves the way for controllable synthesis of MC/PC-TMNs and fundamentally advances the understanding of precursor-guided crystal growth kinetics.