Abstract: Passive autocatalytic recombiners (PARs) utilizes the hydrogen catalytic oxidation reaction mechanism to mitigate the risk of hydrogen deflagration during severe accidents in large pressurized water reactor containment. This study developed a mass transfer-reaction coupled numerical model for H₂/O₂ mixed gas on a platinum (Pt)-based catalyst, systematically analyzing the effects of operational parameters (concentration, temperature, flow rate) and structural parameters (plate spacing, height, thickness) on the comprehensive performance of the plate-type PARs. The results indicate that increasing hydrogen concentration and gas temperature can directly enhance the catalytic reaction rate. When the flow rate increases from 0.2 m/s to 1.0 m/s and the plate spacing enlarges from 8 mm to 15 mm, the increased hydrogen mass flow rate accelerates the catalytic reaction rate, but the hydrogen elimination rate decreases by 16.23% and 9.59%, respectively. The high-activity region at the leading edge of the catalytic plate (﹤30 mm)exhibits a reaction rate an order of magnitude faster than that of the middle and rear sections (﹥75 mm). The variation in the catalytic plate thickness has a minimal impact on hydrogen concentration, and the average temperature difference of the catalytic plate is less than 20 K.