The electrocatalytic decomposition of the abundant and toxic H₂S from industrial by-products is a promising energy conversion technology for H₂ production and simultaneously removing this environmental pollutant. However, the development of such a technology has been hindered by the lack of low-cost, efficient and robust electrocatalysts. Herein, we reported a remarkable graphene-encapsulated metal catalyst, i.e., nitrogen-doped graphene encapsulating a non-precious CoNi nanoalloy as the anode for highly efficient electrocatalytic H₂ production from H₂S. This optimized catalyst could drive the anode reaction at an onset potential of 0.25 V, which was 1.24 V lower than that required for the water oxidation reaction, and delivered almost twice current density than that of Pt/C. Meanwhile, it exhibited approximately 98% H₂ faradaic efficiency and maintained long-term durability for more than 500 h without any decay. The density functional theory calculations revealed that the CoNi and nitrogen dopants synergistically facilitated the formation of polysulfides on graphene's surfaces. Furthermore, a demo showed 1200 h stability for removing H₂S impurities from industrial syngas to produce hydrogen by this graphene-encapsulated metal catalyst, demonstrating its great potential for hydrogen production toward sustainable energy applications.