The dual active site Ni 3Sn 2-NiSnO x alloy-oxide catalysts via Sn-Modulated Ni coordination for efficient ammonia synthesis

As promising non-precious catalysts for the nitrogen reduction reaction (NRR), the nickel (Ni)-based materials have attracted considerable attention due to their unique electronic structure and catalytic activity, nevertheless, the efficiency is hindered by inefficient nitrogen (N2) adsorption and activation due to insufficiently flexible coordination environments. Here in this work, we develop the dual active site Ni3Sn2-NiSnOx alloy-oxide catalysts with succulent-plant-like nanostructure as catalysts via a facile electrochemical deposition strategy. Intriguingly, the Ni3Sn2-NiSnOx catalysts exhibit outstanding NRR performance with a Faradaic efficiency (FE) of 54.36 ± 1.2% and an ammonia yield of 83.33 ± 1.0 μg·h–1·cm–2 in 0.1 M KOH. Meanwhile, the catalysts retain 90% initial activity after 4200 minutes continuous operation at -0.7 V (vs. RHE), showcasing remarkable durability in the alkaline medium. We demonstrate that the introduced high-valent Sn modulates the electronic structure and coordination environment of Ni, effectively reduces its d-band center, and attenuates hydrogen adsorption. We further reveal that the synergistic Ni-Sn interaction in the nanoalloy cooperatively localizes electrons at the Ni-Sn interface via surface oxide-mediated charge redistribution through the combined in-situ spectroscopic measurements and theoretical simulations. These changes collectively suppress the competing hydrogen evolution reaction (HER), thereby boosting the FE for NRR. This work presents a simple synthesis method for alloy-oxide catalyst fabrication and offers mechanistic insights as well as design principles for the development of Ni-based materials NRR electrocatalysts with dual active sites in alkaline environments.