2H → 1T phase engineering of layered tantalum disulphides in electrocatalysis: oxygen reduction reaction

Abstract

Tremendous attention is paid to renewable sources of energy. Transition metal dichalcogenides (TMDs) are intensively studied for their promising catalytic activities in hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR). In this fundamental work, we explore the catalytic properties of TMDs family members: 2H TaS2 and 1T TaS2. Our findings reveal that both polytypes exhibit poor HER performance which is even more pronounced when subjected to electrochemical treatment with reduction/oxidation. Our experimental data show that 1T TaS2 has a lower overpotential at a current density of -10 mA.cm-1, despite our theoretical density functional theory (DFT) calculations indicating that more favorable free energy of hydrogen adsorption should make perfect 2H TaS2 a better HER catalyst. By a thorough characterization, it is shown that the higher conductivity of 1T TaS2 and a slightly higher surface oxidation of 2H TaS2 explains this discrepancy. Moreover the changes in catalytic activity after electrochemical treatment are addressed here. For the oxygen reduction reaction (ORR) the electrochemical treatment leads to an improvement of catalytic properties. With onset potentials similar to that of Pt/C catalyst, TaS2 is found to be an efficient catalyst for oxygen reduction, rather than for proton reduction, in opposite to the behaviour of group VIB layered TMDs.

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ORCID for Tomas Polcar: orcid.org/0000-0002-0863-6287

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