Energy-efficient CO2 hydrogenation with fast response using photoexcitation of CO2 adsorbed on metal catalysts

Abstract

Many heterogeneous catalytic reactions occur at high temperatures, which may cause large energy costs, poor safety, and thermal degradation of catalysts. Here, we propose a light-assisted surface reaction, which catalyze the surface reaction using both light and heat as an energy source. Conventional metal catalysts such as ruthenium, rhodium, platinum, nickel, and copper were tested for CO2 hydrogenation, and ruthenium showed the most distinct change upon light irradiation. CO2 was strongly adsorbed onto ruthenium surface, forming hybrid orbitals. The band gap energy was reduced significantly upon hybridization, enhancing CO2 dissociation. The light-assisted CO2 hydrogenation used only 37% of the total energy with which the CO2 hydrogenation occurred using only thermal energy. The CO2 conversion could be turned on and off completely with a response time of only 3 min, whereas conventional thermal reaction required hours. These unique features can be potentially used for on-demand fuel production with minimal energy input.

Visible Light-Driven Gas-Phase Artificial Photosynthesis Reactions over Ruthenium Metal Nanoparticles Modified with Anatase TiO2

“…In their case, heat was purposefully used alongside light to carry out the hydrogenation of CO 2 over Ru nanoparticles, yielding better overall catalytic performance when both heat and light were used. Therefore, we conclude that the generation of hot electrons from the metallic nanoparticles, the reduced gap between the HOMO and LUMO levels in the adsorbed CO 2 molecules, and the photoinduced thermal energy all work in tandem to promote the CO 2 photoreduction [23][24][25]28].…”

“…Firstly, as reported by Kim et al, upon chemisorption onto the surface of Ru nanoparticles, CO 2 molecules experience a pronounced narrowing in the energy gap between their HOMO (5σ bonding) and LUMO (2π antibonding) levels. They report a decrease from 8.5 eV (free CO 2 ) to 2.4 eV (Ru-bound CO 2 species) [25]. The new energy gap of Ru-CO 2 molecules falls within the visible region; hence, adsorbed CO 2 molecules can absorb the incident irradiation and this can promote the dissociation reaction.…”

“…Furthermore, the photocatalysis over pure Ru nanoparticles may be partially attributed to thermal promotion, since light absorption in the range of the LSPR band will lead to a slight temperature rise within the nanoparticles [27]. The combination of thermal and photoenergies to initiate catalytic processes of CO 2 conversion is deemed beneficial firstly by Thampi et al [13] and recently by Kim et al [25]. In their case, heat was purposefully used alongside light to carry out the hydrogenation of CO 2 over Ru nanoparticles, yielding better overall catalytic performance when both heat and light were used.…”

Photo‐Dissociation of CO2 over Plasmonic RuO2 Nanoparticles

“…Hyunjoo et al have recently claimed that upon chemisorption onto the surface of Ru metal nanoparticles, CO 2 molecules experience a pronounced contraction in the energy gap between their HOMO (5σ bonding) and LUMO (2π anti‐bonding) levels (from 8.5 eV for free CO 2 to 2.4 eV for Ru‐bound CO 2 species). It is possible that such a decrease could also apply upon adsorption of CO 2 on the RuO 2 surface, i. e .…”

Heterogeneous catalysts for catalytic CO2 conversion into value-added chemicals

“…We recently reported light-assisted CO 2 hydrogenation on heterogeneous metal catalysts [94]. Various metals were tested in a photoreactor by changing temperature, light intensity, and light wavelength.…”