This chapter explores the critical role of catalytic materials in advancing the utilization of environmentally friendly propellants for space propulsion applications. Specifically, it focuses on the thermal decomposition and compositions of hydroxylammonium nitrate (HAN) and hydrogen peroxide (H2O2) as green propellants, highlighting their potential for sustainable propulsion systems. The chapter reviews innovative catalysts developed to enhance the thermal decomposition and combustion processes of these propellants, shedding light on the catalytic mechanisms involved. Furthermore, it discusses the practical implementation of HAN and H2O2 as thrusters, demonstrating their feasibility and efficiency in space missions. Through a comprehensive analysis of catalytic materials and their impact on propellant performance, this chapter contributes to the advancement of eco-friendly propulsion technologies, essential for the future of space exploration.