Catalytic Combustion of Extremely Low Concentrations of Methane by Pt/CeO2 {111} Nanocrystals Driven by the Synergy of Photons and Phonons

Abstract

Anthropogenic methane emissions from landfill sites and coal mines with low local concentrations (<5000 ppm) are a critical factor in climate change, and the conversion of such low concentrations of methane has been widely regarded as a thorny issue in catalysis while being pivotal for a sustainable society. Conventional catalytic methane combustion requires high temperatures (>400 °C) and is particularly inefficient at rather low concentrations (<1000 ppm). Herein, Pt/CeO2 {111} nanocrystals assisted by photon-phonon codriven catalysis overcome these challenges. Ultrafast transient absorption spectroscopies confirm that CeO2 {111} efficiently harvests photons and promotes charge separation, while phonons promote the detrapping process and improve the initial charge separation, further enhancing the active charge populations. Meanwhile, Pt works as an efficient electron acceptor, enabling photohole oxidation of methane at the picosecond time scale and accelerating oxygen reduction reactions. All these results lead to a low light-off temperature T80 of 98 °C and a one-pass methane combustion efficiency of 95% with CO2 selectivity of near 100% at 200 °C, together with an apparent quantum efficiency of 36.5% and long-term stability over 100 h in the presence of even rather low methane concentrations of 500 ppm. These findings establish a scalable strategy for the efficient abatement of low-concentration methane emissions under mild conditions.