In the pursue of a carbon-free economy, the utilization of fuels with low or zero carbon footprint account for only 1% of global final energy demand, a share that is predicted to follow a dramatic growth to 20% by 2050. Ammonia (NH₃) has become dominant in the international transportation and storage of low-carbon alternative fuels. NH₃ is regarded as an alternative fuel, as a carbon-free fuel, and renewable hydrogen (H₂) carrier with high energy density, and its production and distribution infrastructure are well established. However, a current challenge is that NH₃ has a lower burning velocity and a narrow flammability limit. Thus, the use of NH₃ has numerous limitations in practical combustion applications. Blending NH₃ with H₂ is considered a solution that has been proposed to enhance NH₃ combustion by improving ignition, flammability, and H₂ safety issue. Using NH₃ blended with H₂ as a fuel in combustion systems is a practical approach to decarbonizing the energy sector.

Thus, this review highlights the existing influential studies and ongoing research on NH₃/H₂ blended fuels. The review covers NH₃ assists the safety behaviour of H₂ use, in-situ NH₃ dissociation, NH₃ and H₂ properties, NH₃/H₂ combustion characterization, techniques for low NO_x NH₃/H₂ combustion, and challenges for NH₃/H₂ combustion. Finally, recommendations for future studies are provided for further developing the utilization of NH₃/H₂ as blended fuel.