Dynamic Etching‐Induced Cl‐Terminated Ti ₃ C ₂ Cl _x /Ti ₃ ZnC ₂ Heterostructure for Ammonia Electrosynthesis and Zinc‐Nitrogen Batteries

2D Ti₃C₂T_x MXenes are of great potential in catalysis, energy storage, and conversion, yet the controlled tuning of their structure, intrinsic activity, and stability remains a challenge. Herein, we address this challenge through a dual-modification strategy, synthesizing a Cl-terminated MXene/MAX (Ti₃C₂Cl_x/Ti₃ZnC₂) heterostructure by a dynamic etching approach for efficient electrocatalytic nitrogen reduction reaction (NRR). This catalyst achieves an NH₃ yield of 20.1 µg h^-1 mg^-1 and a Faradaic efficiency of 38.1% at -0.2 V vs. RHE in 0.1 m KOH electrolyte, with high stability for over 70 h, positioning it among the top-performing MXene-based NRR electrocatalysts. Experimental and theoretical analyses demonstrate that the Ti₃C₂Cl_x/Ti₃ZnC₂ heterostructure modulates the electronic structure of Ti sites, thus optimizing the intermediate adsorption and reducing the energy barrier of *NH₂ → NH₃ conversion in the distal pathway to 0.7 eV. The Zn-N₂ battery assembled with Ti₃C₂Cl_x/Ti₃ZnC₂ can reach a peak power density of 36.5 µW cm^-2, with an NH₃ yield of 13.1 µg h^-1 mg^-1. This study has demonstrated that the dual modification strategy involving surface terminations regulation and heterostructure construction is effective to improve both NRR activity and stability of MXene-based electrocatalysts, which is crucial for efficient NH₃ production and energy generation. This improvement paves the way for efficient ammonia and energy co-generation, providing a viable materials design strategy and deeper mechanistic insights.