Plasma-Derived Atomic\nHydrogen Enables Eley–Rideal-Type\nCO<sub>2</sub> Methanation at Low Temperatures

Activating H<sub>2</sub> molecules into atomic hydrogen\nand utilizing\ntheir intrinsic chemical reactivity are important processes in catalytic\nhydrogenation. Here, we have developed a plasma-catalyst combined\nsystem that directly provides atomic hydrogen from the gas phase to\nthe catalytic reaction to utilize the high energy and translational\nfreedom of atomic hydrogen. In this system, we show that the temperature\nof CO<sub>2</sub> methanation over Ni/Al<sub>2</sub>O<sub>3</sub> can\nbe dramatically lower compared to thermal catalysis. Using a detailed\nmechanistic study with kinetic studies, laser plasma diagnostics, <i>in situ</i> plasma surface characterization, and theoretical\ncalculations, we revealed that plasma-derived atomic hydrogen (PDAH)\nplays a crucial role in reaction promotion. In particular, PDAH effectively\nlowers the energy barrier of bidentate formate hydrogenation by translating\nfrom the Langmuir–Hinshelwood to the Eley–Rideal-type\nreaction.