Low-temperature plasma-assisted ammonia decomposition catalyzed with bimetallic catalysts: Kinetic study and energy-efficiency analysis

Low efficiency in hydrogen transportation and storage remains a major challenge for its use as a renewable energy carrier. Due to its high hydrogen density and ease of liquefaction, ammonia is emerging as an efficient and cost-effective hydrogen carrier. At the point of use, ammonia is normally decomposed to release hydrogen for various energy applications. However, traditional thermal-catalytic ammonia decomposition is energy-intensive. In this study, low content (2.5 wt%) noble metal ruthenium enhanced non-precious metals like nickel, iron, or cobalt were employed as catalysts in a low-temperature plasma system with dielectric barrier discharge for ammonia decomposition. Experimental parameters, including temperature, catalyst loading, and gaseous hourly space velocity (GHSV), etc., were investigated and optimized. Metal component interactions were revealed in the study. Reaction orders and apparent decomposition activation energies were determined via kinetic studies. Plasma-assisted catalytic decomposition of ammonia under Ru-promoted non-precious catalysts offers a viable solution for hydrogen release from NH3 for hybrid combustion or on-board vehicle applications. Taking Ru–Ni–Ce/Al2O3 catalyst as a sample, the introduction of plasma significantly reduced the activation energy from 89 kJ/mol of traditional thermal catalytic process to 43.56 kJ/mol of this study, achieving high hydrogen production energy efficiency of 66.04 % (77.60 mol-H2/kWh or 69.58 kJ/mol-NH3), compared to 55.57 % (82.69 kJ/mol-NH3) for conventional methods.