(682d) Fundamental Insights into Non-Oxidative Methane Conversion on Group III-Nitrides

Group III-nitrides (e.g., AlN, GaN, InN) are the only known semiconductors whose band edges straddle a wide range of redox potentials.¹ This has rendered them suitable for various photocatalytic transformations including selective methane conversion to aromatics (6CH₄ ↔ C₆H₆ + 9H₂).^1-3 Previous studies have used epitaxially grown GaN with low-surface areas as thermal- and photocatalysts for this reaction showing promising performance compared to common catalysts such as Mo/ZSM-5.^2,3 However, limited insights exist into the mechanisms associated with thermal and photocatalytic methane dehydroaromatization (MDA) on epitaxially grown nitrides.^2,3 Consequently, there is a need for development of solution-based synthetic tools that can aid in controlled synthesis of these nitrides, with high surface areas to enable detailed catalytic and spectroscopic investigation of non-oxidative methane conversion.

Herein, a robust hydrothermal approach to synthesize GaN has been developed which leads to rod-shaped GaN nanostructures, with well-defined surfaces and high surface areas.⁴ The influence of metal co-catalysts (M=Rh, Mo, Re, Ru) supported on the surface of nanostructured GaN are also systematically investigated. Detailed kinetic, microscopic and spectroscopic studies are employed with the goal of identifying the factors that control MDA activity on these heterostructures. The effect of partial pressures, temperature, wavelength and intensity of the incident radiation are used to understand the origin of both thermal and photocatalytic activity of M/GaN structures towards MDA. Our findings provide important insights into the role of the metal co-catalyst, and the support structure, on the thermal and photocatalytic non-oxidative methane activation.

References:

[1] Kibria, M.; Mi, Z. J. Mater. Chem. A 2016, 4, 2801-2820.

[2] Li, L.; Fan, S.; Mi, Z.; J. Am. Chem. Soc. 2014, 136, 7793-7796.

[3] Li, L.; Mu, X.; Mi, Z.; Li, C. Angew. Chem. 2014, 126, 14330-14333.

[4] Bao, K.; Liu; W.; Wang, A.; et al. Appl. Surf. Sci. 2012, 263, 682-687.