<p>Establishing supply chains for future ammonia energy systems requires the development of efficient materials and processes for ammonia production under mild conditions. Recent researches disclose unique functionalities of binary alkali and alkaline earth metal hydrides in mediating ammonia synthesis. Thanks to the rich compositional and structural properties of the metal-hydrogen system, we herein report that LiBaH₃, as a narrow band gap perovskite hydride, exhibits a strong response to visible light illumination. Specifically, hydridic hydrogen undergoes reductive elimination of producing H₂ and creates an electron-rich surface. Such an environment favors dinitrogen fixation to form N–H bonds. Based on this chemical property, a chemical looping ammonia synthesis process mediated by LiBaH₃ and driven by both photo and thermal energies was proposed and evaluated. This work demonstrates that hydride perovskites are promising candidates for mediating photo-assisted nitrogen fixation reactions.</p>