Palladium Married with MBene Multilayers: Enabling Intensified Hydrogen Spillover for Efficient Nitrite‐to‐Ammonia Electroreduction

Abstract Electrochemical nitrite reduction reaction (NO ₂ RR) has emerged as a promising alternative approach for ammonia (NH ₃ ) production, offering both energy efficiency and environmental sustainability. The rational regulation of active hydrogen (*H) is pivotal for NO ₂ ⁻ ‐to‐NH ₃ conversion, yet it remains a significant challenge in the context of NO ₂ RR. In this study, molybdenum boride (MBene) multilayers are introduced as an electronic support to integrate with palladium (Pd) nanoparticles, creating dual catalytic sites that effectively balance the adsorption of *H and *NO ₂ ⁻ , thereby enabling synergistic catalysis of the NO ₂ RR. Theoretical and experimental analyses revealed that *H is efficiently generated on Pd sites and subsequently undergoes spillover to *NO ₂ ⁻ ‐adsorbed MBene surfaces, facilitating accelerated hydrogenation and NH ₃ synthesis. Consequently, the Pd/MBene catalyst demonstrated exceptional performance, achieving a high NH ₃ Faradaic efficiency of 89%, an NH ₃ yield rate of 16.9 mg h ⁻¹ mg _cat ⁻¹ , and remarkable cycling stability at a low applied potential of ‐0.3 V versus RHE. Motivated by the outstanding NO ₂ RR performance, the Pd/MBene catalyst is further utilized as the cathode catalyst to construct Zn‐nitrite and formaldehyde‐nitrite batteries. These systems demonstrated the dual functionality of simultaneous NH ₃ production and electricity generation, highlighting the potential of Pd/MBene as a versatile and efficient catalyst for sustainable energy conversion.