Highly Efficient Nitrogen Electroreduction on Cr-Doped ReS2 via Synergistic Dopant-Vacancy Pairs

The electrochemical nitrogen reduction reaction (NRR) offers a sustainable route for ammonia production under ambient conditions, but its efficiency remains limited by sluggish N2 activation and competition from the hydrogen evolution reaction (HER). Rhenium disulfide (ReS2), characterized by weak interlayer coupling and an anisotropic electronic structure, provides a promising platform for nitrogen electrocatalysis; however, the limited abundance and insufficient reactivity of its intrinsic active sites restrict its NRR performance. Here, we introduce a Cr-Vs (sulfur vacancy) pair engineering strategy that transforms the local coordination environment of ReS2 into an electronically differentiated active site. Cr incorporation thermodynamically facilitates the Vs formation, generating a reconstructed Cr-Vs configurations with substantially modified local electronic states. This reconstruction optimizes Re 5d-N 2p orbital hybridization, thereby selectively stabilizing key hydrogenated nitrogen intermediates. Meanwhile, the Cr-Vs pair selectively tunes the competition between NRR and HER, preferentially enhancing the intrinsic NRR activity. Consequently, the optimized RSC-5 catalyst delivers an NH3 yield rate of 67.70 ± 0.72 μg mg-1cat. h-1 and a Faraday efficiency of 10.53 ± 0.38%. This work establishes dopant-vacancy coupling as a generalizable strategy for reconstructing local coordination and decoupling competing reaction pathways, offering design principles for developing selective electrocatalysts for sustainable ammonia synthesis.