Use of H2S to Probe the Active Sites in FeNC Catalysts for the Oxygen Reduction Reaction (ORR) in Acidic Media

• Published in: ACS catalysis Vol. 4; no. 10; pp. 3454 - 3462
• Main Authors: Singh, Deepika, Mamtani, Kuldeep, Bruening, Christopher R, Miller, Jeffrey T, Ozkan, Umit S
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 03.10.2014
• Subjects: CNx; FeNC; H2S; ORR; sulfur deactivation; H2S; sulfur deactivation; CN x; FeNC; ORR
• ISSN: 2155-5435; 2155-5435
• DOI: 10.1021/cs500612k

H2S has been used as a probe molecule both in an “in situ” poisoning experiment and in intermediate-temperature heat-treatment steps during and after the preparation of FeNC catalysts in an attempt to analyze its effect on their ORR activity. The heat treatments were employed either on the ball-milled precursor of FeNC or after the Ar-NH3 high temperature heat treatments. ORR activity of the H2S-treated catalysts was seen to be significantly lower than the sulfur-free catalysts, whether the sulfur exposure was during a half-cell testing, or as an intermediate-temperature exposure to H2S. The incorporation of sulfur species and interaction of Fe with sulfur were confirmed by characterization using XPS, EXAFS, TPO, and TPD. This study provides crucial evidence regarding differences in active sites in FeNC versus nitrogen-containing carbon nanostructured (CN x ) catalysts.