Nanotechnologies / Materials
Catalysis chemistry, Petroleum chemistry, Carbon neutral

Development of advanced catalytic technology for utilizationof carbon dioxide using light energy
Division of Materials and Manufacturing Science, Graduate School of Engineering
Associate Professor Yasutaka Kuwahara

https://researchmap.jp/yasutakakuwahara/

Professor Hiromi Yamashita

https://researchmap.jp/read0118536

Nanotechnologies / Materials

Abstract
Carbon dioxide (CO2) is considered to be the main cause of
global warming, and efforts have been devoted to reduce its emissions on a global scale. Carbon monoxide (CO), which is obtainedby hydrogenation of CO2, is a useful chemical raw material for liquid hydrocarbons such as alcohol, gasoline, jet fuel, etc. The reaction of CO2 with hydrogen (H2) to obtain CO (reverse water-gas shiftreaction) conventionally requires a temperature higher than 500℃.
We have discovered that CO can be obtained efficiently and selectively from CO2 and H2 at around 140℃ using a catalyst consistingof platinum (Pt) nanoparticles supported on a molybdenum andtungsten composite oxide. Furthermore, we found that the reaction
rate significantly increased when the catalyst was irradiated withlight.

this technology is expected to be a clean CO2 conversion technology for the realization of a carbon-neutral society.

▍ Background & Results
CO2 is considered to be a major contributor to global warming,and efforts have been devoted to reduce its emissions on a global
scale. Japanese government declared an intention to achieve zero
emissions of greenhouse gases including CO2 by 2050. To achieve
this goal, development of technologies to recover CO2 as a carbon
resource and utilize it as a useful material (CO2 capture and utilization technology) has been required. If CO2 can be efficiently converted to CO, it will be possible to produce useful substances while
reducing CO2 emissions, thereby contributing to the problems ofglobal warming and depletion of fossil resources. However, the reaction to produce CO by reacting CO2 with H2 (reverse water-gas
shift reaction, equation: (CO2 + H2 = CO + H2O) conventionallyrequires a high temperature of 500℃ or higher, and only a low reaction rate can be obtained at low temperatures due to equilibrium
constraints.
We have found that CO can be selectively and efficiently generated even at a lower temperature of 140°
C, a much lower temperature than that reported earlier, when a molybdenum and tungsten
composite oxide catalyst loaded with platinum (Pt) nanoparticles
is used for the reverse water-gas shift reaction, because of the lattice oxygen defects formed in the composite oxide. Furthermore,
the reaction rate is dramatically enhanced when the catalyst is
irradiated with visible light. Molybdenum and tungsten composite
oxides have excellent photothermal conversion properties, thereby
the catalyst is locally heated under light irradiation, to promote thereverse water-gas shift reaction, resulting in a high CO productionrate.

▍ Significance of the research and Future perspective
The catalyst has abilities to operate even near the temperature ofwaste heat emitted from industry and to increase the reaction rateusing inexhaustible solar energy. Since CO2 can be converted into
industrially useful substances using waste heat and solar energy,

P a t e n t Japanese Patent Application No. 2020-093711
Ge, Hao; Kuwahara, Yasutaka; Yamashita, Hiromi et al. Enhanced Visible-NIR Absorption and Oxygen Vacancy Generation of Pt/HxMoWOy by H-spillover
to Facilitate Photothermal Catalytic CO2 Hydrogenation. Journal of Materials Chemistry A. 2022, 10 (20), p.10854-10864. doi: 10.1039/d2ta01595a
Ge, Hao; Kuwahara, Yasutaka; Yamashita, Hiromi et al. Plasmon-induced Catalytic CO2 Hydrogenation by a Nano-sheet Pt/HxMoO3-y Hybrid with Abundant
Tr e a t i s e
Surface Oxygen Vacancies. Journal of Materials Chemistry A. 2021, 9(24), p.13898-13907. doi: 10.1039/d1ta02277f
Kuwahara, Yasutaka; Mihogi, Takashi; Yamashita, Hiromi et al. A Quasi-stable Molybdenum Sub-oxide with Abundant Oxygen Vacancies that Promotes
CO2 Hydrogenation to Methanol. Chemical Science. 2021, 12(29), p.9902-9915. doi: 10.1039/d1sc02550c
UR
L https://resou.osaka-u.ac.jp/ja/research/2021/20210526_2
K e y w o r d CO2 capture and utilization, CO2 reutilization, molybdenum oxide, light energy utilization