This paper presents a novel pneumatic generator based on the catalytic decomposition of hydrogen peroxide for producing the pressurized gas for mobile robotic systems driven by pneumatic actuators, thus replacing portable air compressors driven by electric motors. By adopting a pressure-feedback mechanism, hydrogen peroxide is autonomously self-injected into the catalytic reactor without the use of additional injection mechanisms such as electric micropumps. Additionally, the dynamic behavior of pressure generation is illustrated by both an analytic model and experiments. It is experimentally demonstrated that the proposed system has a considerably higher power density than a battery and electrical motor system.