Electron-Rich Nickel Enabled by Charge Transfer in Multimetal Nanostructures for Efficient Ammonia-to-Hydrogen Conversion.

Achieving noble-metal-like reactivity in earth-abundant catalysts requires materials platforms that can simultaneously stabilize active sites and program their electronic states. Ammonia-to-hydrogen conversion is a demanding example, because Ru-free catalysts must overcome the intrinsically sluggish kinetics of ammonia decomposition. Here, we report a catalyst design that couples precursor-level cation mixing and active-site dispersion with charge-transfer engineering of Ni to address this challenge. Density functional theory calculations identify Cr as the most effective electron-donating promoter for Ni among metal cations incorporable into the precursor framework. Guided by this prediction, we construct a NiCrAl reduced mixed-metal oxide catalyst in which atomically mixed precursors stabilize highly dispersed Ni species, while Cr-to-Ni charge transfer generates electron-rich Ni active sites. Multiscale spectroscopic analyses verify this electronic modulation, and combined theoretical and in situ mechanistic analyses indicate that electron-rich Ni favors NH3 adsorption in a reaction-relevant Lewis-acid configuration, favorably modifies the dehydrogenation energetics, and weakens N2 binding to facilitate product desorption. NiCrAl-RMMO reaches 95.5% NH3 conversion at 550°C and 22.83 mmol H2 gcat -1 min-1 at 500°C, with stable operation over 100 h. More broadly, this work establishes charge-transfer engineering in LDH-derived mixed-metal nanostructures as a general strategy for designing high-performance, Ru-free catalysts for ammonia-to-hydrogen conversion.