5 years ago

2H1T Phase Engineering of Layered Tantalum Disulfides in Electrocatalysis: Oxygen Reduction Reaction

2H1T Phase Engineering of Layered Tantalum Disulfides in Electrocatalysis: Oxygen Reduction Reaction
Jan Luxa, Zdeněk Sofer, Petr Lazar, Tomáš Polcar, Martin Pumera, David Sedmidubský, Vlastimil Mazánek, Mauro Callisti
Tremendous attention is currently being paid to renewable sources of energy. Transition-metal dichalcogenides (TMDs) have been intensively studied for their promising catalytic activities in the hydrogen evolution reaction (HER) and the oxygen reduction reaction (ORR). In this fundamental work, we explored the catalytic properties of TMD family members 2H TaS2 and 1T TaS2. Our findings reveal that both polytypes exhibit poor HER performance, which is even more pronounced after electrochemical reduction/oxidation. Our experimental data show that 1T TaS2 has a lower overpotential at a current density of −10 mA cm−1, despite theoretical DFT calculations that indicated that the more favorable free energy of hydrogen adsorption should make “perfect” 2H TaS2 a better HER catalyst. Thorough characterization showed that the higher conductivity of 1T TaS2 and a slightly higher surface oxidation of 2H TaS2 explains this discrepancy. Moreover, changes in the catalytic activity after electrochemical treatment are addressed here. For the ORR in an alkaline environment, the electrochemical treatment led to an improvement in catalytic properties. With onset potentials similar to that of Pt/C catalysts, TaS2 was found to be an efficient catalyst for the ORR, rather than for proton reduction, in contrast to the behavior of Group 6 layered TMDs. The right phase? Transition-metal chalcogenides (TMDs) have promising applications in electrocatalysis. The activity of TMDs 2H TaS2 and 1T TaS2 in the oxygen reduction reaction (ORR) and the hydrogen evolution reaction (HER) have been explored. Both phases showed poor HER activity, but good ORR activity, comparable to that of commercial Pt/C. DFT calculations were used to clarify the surprisingly low HER activity of 1T TaS2.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1002/chem.201701494

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