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Activity and Stability Relationship for Anion Doped CoS x Se 2-X Dichalcogenides for the Hydrogen Evolution Reaction
Journal article

Activity and Stability Relationship for Anion Doped CoS x Se 2-X Dichalcogenides for the Hydrogen Evolution Reaction

Yawei Li, Swarnendu Chatterjee and Joshua David Snyder
Meeting abstracts (Electrochemical Society), v MA2018-01(29), pp 1660-1660
13 Apr 2018
DOI: https://doi.org/10.1149/MA2018-01/29/1660

Abstract

As an ideal clean energy carrier, hydrogen can be produced through polymer electrolyte membrane (PEM) electrolysis by generating H 2 from H 2 O. However, noble platinum group metals (PGM) remain the most common electrocatalysts for hydrogen evolution reaction (HER). The expense and scarcity of these catalytic materials obstruct the wide-spread adoption of electrochemical fuel generation technologies 1 . Sulfur based transition metal dichalcogenides (TMDs) have emerged as a promising alternative to PGM HER electrocatalysts as they are abundant, inexpensive, and exhibit a low HER overpotential in acidic environment 2,3 . Here we present a systemic assessment of the compositional dependent HER activity and stability for Co-based mixed chalcogen, CoS x Se 2-x , pyrite TMDs. We observe a decrease in HER activity from the single chalcogen TMDs, CoS 2 and CoSe 2 , to mixed chalcogen TMDs, as shown in Figure 1. This observed compositional trend in HER activity can be explained by the unique combination of compositional dependent hydrogen adsorption free energy (ΔG Had ) and bulk resistivity/conductivity of the pyrite TMD. With near thermoneutral ΔG Had , the highest resistivity among the compositions was observed. The following increase in Se content leads to the decrease in HER activity due to a steady movement away from optimal ΔG Had . As the composition approaches CoSe 2 , however, it is observed that HER activity again increases at higher Se contents, with CoSe 2 exhibiting similar activity to CoS 2 . This highlights the convolution of ΔG Had and material conductivity in determining the HER activity. Furthermore, through stability tests under constant potential HER electrolysis, as shown in Figure 2, Se-rich Co-based pyrite TMDs are found to be more durable than S-rich samples. Therefore, with an HER activity matching that of CoS 2 , but with a dramatic improvement in stability, CoSe 2 breaks away from the traditional inverse activity/stability relationship and represents a promising material for non-PGM HER electrocatalysis in acidic based PEM electrolyzers. Wang, J. et al. Mater. 28, (2016) 215-230. Chhowalla, H. et al. Nature Chemistry 5, (2013) 263-275. Jaramillo, T. et al. Science 317, (2007) 100-102. Figure 1

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