In situ reduction-driven formation of sub-nanometer alternating heterostructures

Sub-nanometer alternating heterostructures provide a platform for modulating electronic structure and interfacial reactivity through strong atom-level coupling, with potential applications in energy conversion. However, their precise construction remains challenging. Here we show a strategy for constructing sub-nanometer alternating heterostructures through confined spinodal decomposition and ligand-mediated in situ reduction. Oleylamine ligands adsorbed on NiMoO₄ sub-nanowires act as mild reductants, selectively reducing Ni²⁺ to spatially confined metallic Ni domains and forming coherent Ni/NiMoO₄ heterointerfaces. Experimental and theoretical analyses suggest that the Ni/NiMoO₄ interfaces modify the local electronic structure and facilitate the adsorption and activation of hydrogen evolution intermediates. The resulting catalyst requires an overpotential of 14.4 ± 2.9 mV to reach 10 mA cm^-2 in 1 M KOH and delivers 2 A cm^-2 at 1.62 V in an anion-exchange membrane electrolyzer at 80 ^oC, with stable operation over 2200 h at 25 °C. These findings provide insights into the construction and interfacial regulation of sub-nanometer heterostructures through in situ reduction.