Abstract
Utilization of the renewable energy sources is one of the main challenges in the state-of-the-art technologies for CO2 recycling. Here we have taken advantage of the solar light harvesting in the thermocatalytic approach to carbon dioxide methanation. The large-surface-area Ni/CeO2 catalyst produced by a scalable low-cost method was characterized and tested in the dark and under solar light irradiation conditions. Light-assisted CO2 conversion experiments as well as in-situ DRIFT spectrometry, performed at different illumination intensities, have revealed a dual effect of the incident photons on the catalytic properties of the two-component Ni/CeO2 catalyst. On the one hand, absorbed photons induce a localized surface plasmon resonance in the Ni nanoparticles followed by dissipation of the heat to the oxide matrix. On the other hand, the illumination activates the photocatalytic properties of the CeO2 support, which leads to an increase in the concentration of the intermediates being precursor for methane production. Analysis of the methane production at different temperatures and illumination conditions has shown that the methanation reaction in our case is controlled by a photothermally-activated process. The used approach has allowed us to increase the reaction rate up to 2.4 times and consequently to decrease the power consumption by 20 % under solar illumination, thus replacing the conventional thermal activation of the reaction with a green energy source.
Highlights
Conversion of carbon dioxide to renewable hydrocarbon fuels, such as methane, is a big challenge nowadays due to the high thermodynamic stability of the CO2 molecule and, major difficulties in its reduction [1,2,3]
Except for the standard pho tocatalytic approach, based on the metal-decorated metal oxides, where the metal oxide support is used as the main photoabsorber and metallic nanoparticles act only as active catalytic sites [16,17], a rapidly emerging field in catalysis is taking advantage of the strong light extinction of the metallic nanoparticles themselves, owning to the effect called localized surface plasmon resonance (LSPR) [18,19]
High angle annular darkfield (HAADF) scanning TEM (STEM) was combined with electron energy loss spectros copy (EELS) in the Tecnai microscope by using a GATAN QUANTUM filter
Summary
Conversion of carbon dioxide to renewable hydrocarbon fuels, such as methane, is a big challenge nowadays due to the high thermodynamic stability of the CO2 molecule and, major difficulties in its reduction [1,2,3]. Excited LSPR is followed by a strong near-field enhancement, which is damped through one of the possible mechanisms: i) radiative decay through re-emitting of the photons; ii) Landau damping, resulting in a non-equilibrium charge distribution (so-called “hot electrons” or “hot holes”, which can be transferred to the metal-oxide support or directly participate in the catalytic reaction); or iii) direct excitation of electron-hole pairs in the semiconductor through plasmon-induced resonant energy transfer (PIRET). Another effect that has been recently introduced, consists in direct metal-to-semiconductor charge transfer [31,32]. A complete understanding of these phenomena is fundamental for the new design of efficient plasmonic NP-semiconductor-based catalysts for thermally driven methanation reactors
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