Multivalent Sulfur Vacancy-Rich NiCo₂S₄@MnO₂ Urchin-Like Heterostructures for Ambient Electrochemical N₂ Reduction to NH₃

Innovative advances in the exploitation of effective electrocatalytic materials for the reduction of nitrogen (N₂) to ammonia (NH₃) are highly required for the sustainable production of fertilizers and zero-carbon emission fuel. In order to achieve zero-carbon footprints and renewable NH₃ production, electrochemical N₂ reduction reaction (NRR) provides a favorable energy-saving alternative but it requires more active, efficient, and selective catalysts. In current work, sulfur vacancy (Sv)-rich NiCo₂S₄@MnO₂ heterostructures are efficaciously fabricated via a facile hydrothermal approach followed by heat treatment. The urchin-like Sv-NiCo₂S₄@MnO₂ heterostructures serve as cathodes, which demonstrate an optimal NH₃ yield of 57.31 µg h^-1 mg_cat ^-1 and Faradaic efficiency of 20.55% at -0.2 V versus reversible hydrogen electrode (RHE) in basic electrolyte owing to the synergistic interactions between Sv-NiCo₂S₄ and MnO₂. Density functional theory (DFT) simulation further verifies that Co-sites of urchin-like Sv-NiCo₂S₄@MnO₂ heterostructures are beneficial to lowering the energy threshold for N₂ adsorption and successive protonation. Distinctive micro/nano-architectures exhibit high NRR electrocatalytic activities that might motivate researchers to explore and concentrate on the development of heterostructures for ambient electrocatalytic NH₃ generation.