Interfacial Interaction between the Ruthenium(IV) Oxide Cluster and Graphitic Carbon Nitride Governing the Photocatalytic Activity

R Ohira and SI Naya and M Fujishima and H Tada, JOURNAL OF PHYSICAL CHEMISTRY C, 127, 22076-22084 (2023).

DOI: 10.1021/acs.jpcc.3c05867

Graphitic carbon nitride (g-C3N4) has attracted much interest as a metal-free photocatalyst material responsive to visible light. g-C3N4 possesses a rhombus 2D-unit cell with similar to 1.4 nm on one side. This study has shown that RuO2 clusters with a mean size (d(RuO2)) of similar to 1.5 nm can be formed on g-C3N4 in a highly dispersed state by a solvothermal method at 453 K (RuO2 CL/g-C3N4), while the conventional impregnation method yields significantly larger RuO2 particles (d(RuO2) = 6.5 nm) in an aggregated state (RuO2 NP/g-C3N4). As a test photocatalytic reaction, the conversion from acetic acid to methane, the so-called "photo-Kolbe reaction", was carried out. Illumination of simulated sunlight (AM 1.5, 1 sun) of g-C3N4 in an acetic acid aqueous solution yields methane and carbon dioxide as the major products, and the photocatalytic activity is drastically enhanced by loading RuO2 particles on g-C3N4. RuO2 CL/g-C3N4 exhibits higher activity than RuO2 NP/g-C3N4 by approximately 2 orders of magnitude. Molecular dynamics simulations for a model of RuO2 CL/g-C3N4 show that RuO2 CL is strongly adsorbed on the g-C3N4 surface through the Ru-C and Ru-N bonds without changing the adsorbed position even at 800 K. The origin of the striking photocatalytic activity of RuO2 CL/g-C3N4 is discussed in terms of the interaction between RuO2 and g-C3N4.

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