Reinforcing the Efficiency of Photothermal Catalytic CO 2 Methanation through Integration of Ru Nanoparticles with Photothermal MnCo 2 O 4 Nanosheets.

Carbon dioxide (CO 2 ) hydrogenation to methane (CH 4 ) is regarded as a promising approach for CO 2 utilization, whereas achieving desirable conversion efficiency under mild conditions remains a significant challenge. Herein, we have identified ultrasmall Ru nanoparticles (∼2.5 nm) anchored on MnCo 2 O 4 nanosheets as prospective photothermal catalysts for CO 2 methanation at ambient pressure with light irradiation. Our findings revealed that MnCo 2 O 4 nanosheets exhibit dual functionality as photothermal substrates for localized temperature enhancement and photocatalysts for electron donation. As such, the optimized Ru/MnCo 2 O 4 -2 gave a high CH 4 production rate of 66.3 mmol g cat -1 h -1 (corresponding to 5.1 mol g Ru -1 h -1 ) with 96% CH 4 selectivity at 230 °C under ambient pressure and light irradiation (420-780 nm, 1.25 W cm -2 ), outperforming most reported plasmonic metal-based catalysts. The mechanisms behind the intriguing photothermal catalytic performance improvement were substantiated through a comprehensive investigation involving experimental characterizations, numerical simulations and density functional theory (DFT) calculations, which unveiled the synergistic effects of enhanced charge separation efficiency, improved reaction kinetics, facilitated reactant adsorption/activation and accelerated intermediate conversion under light irradiation over Ru/MnCo 2 O 4 . A comparison study showed that, with identical external input energy during the reaction, Ru/MnCo 2 O 4 -2 had a much higher catalytic efficiency compared to Ru/TiO 2 and Ru/Al 2 O 3 . This study underscores the pivotal role played by photothermal supports and is believed to engender a heightened interest in plasmonic metal nanoparticles anchored on photothermal substrates for CO 2 methanation under mild conditions.