As the size of the metal cluster decreases to a sub-nanometer scale and ultimately to an atomic level, the catalytic properties can be drastically changed. This can provide unique opportunities for tuning activity and chemoselectivity. Because the atomically dispersed catalysts are unstable, metal oxide supports providing strong metal-support interactions are indispensable for their preparation. Metal oxides are suitable for thermochemical reactions, but not appropriate for electrocatalysis due to low conductivity and stability under acidic electrolyte solution. In contrast, carbons, generally accepted as an ideal support for electrocatalysis, cannot stabilize tiny metal species due to the lack of metal-support interaction. In the present work, atomically dispersed Pt catalyst was selectively synthesized via conventional wet-impregnation on zeolite-templated carbon (ZTC) containing a large amount (up to 17 wt%) of sulfur (S). The abundant S and unique carbon structure (i.e., curved 3D networks of graphene) could stabilize a high loading of Pt (5 wt%) in the form of atomically dispersed Pt (Figure 1). HAADF-STEM and EXAFS analyses confirmed that atomically dispersed Pt species are selectively supported without appreciable clustering. In the ORR, Pt/S-ZTC showed an onset potential of 0.71 VRHE, close to the thermodynamic potential of H2O2 production (E°O2/H2O2 = 0.69 VSHE). The Pt/S-ZTC produced H2O2 with up to 96 % selectivity. This indicates that Pt/S-ZTC catalyzes the ORR reaction predominately through a 2-electron pathway (n = 2.1). Consequently, the catalyst can be considered as a promising approach for the production of H2O2, while at the same time generating electricity as a byproduct of fuel cells.

Electrochemical oxygen reduction by atomically dispersed Pt on sulfur-doped zeolite-templated carbons: Selective production of H2O2 instead of H2O

254th National Meeting (2017)

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