In:
ECS Meeting Abstracts, The Electrochemical Society, Vol. MA2020-01, No. 37 ( 2020-05-01), p. 1579-1579
Abstract:
With growing demands for sustainable energy sources, hydrogen energy is receiving great attention due to their abundant, eco-friendly, and renewable nature. Although water electrolysis is most promising technologies for hydrogen production, it is currently obstructed by the sluggish kinetic of oxygen evolution reaction (OER) compared with hydrogen evolution reaction (HER). Furthermore, according to the demand for simplicity and cost effectiveness of electrolysis, the need for bifunctional electrocatalysts which operate in the same electrolyzer, is rapidly increasing. The cubic pyrite-phase transition metal dichalcogenides, such as FeS 2 , NiS 2 , and CoS 2 , have been proposed as candidates for bifuctional electrocatalysts. Among them, CoS 2 has been reported to exhibit high conductivity and high activity for HER and OER in strong alkaline condition. In this study, while there are many phases of cobalt sulfide (e.g., CoS, Co 9 S 8 , and CoS 2 etc.), it was successfully controlled cobalt sulfide phase according to the sulfur ratio through predicted synthesis based on thermodynamic. A highly porous CoS 2 nanoparticles (NPs) was directly synthesized by controlling the ratio of sulfur and cobalt Prussian blue analogues (Co 3 [Co(CN) 6 ] 2 ), one of the metal organic frameworks (MOFs). MOF-driven CoS 2 could lead to improvements in catalytic activity. The newly-designed MOF-driven CoS 2 OER, HER catalysts show distinct strong points. First, CoS 2 is as one of transition metal compounds and has high catalytic activity. Furthermore, the CoS 2 of this work shows a highly porous and uniform particle size because it was synthesized through MOFs using precipitation. The Co 3 [Co(CN) 6 ] 2 was used as the starting material before sulfurization. The Co 3 [Co(CN) 6 ] 2 was prepared through a facile precipitation method. The CoS 2 NPs were synthesized through gas-solid reaction in vacuum system. A 5 mL size ampoule containing total 45 mg of a 2:1 mixture of Co 3 [Co(CN) 6 ] 2 and sulfur powders was arranged, then the ampoule was vacuumed to 10 -2 torr. The prepared ampoule was annealed at 500 ℃ for 2 hr in a furnace at ramping rate of 5 ℃ min -1 . The average powder size of synthesized CoS 2 NPs was approximately 30 nm with ~ 4nm pores, resulting in a large surface area of 915.6 m 2 g -1 . Compared to commercial IrO 2 , CoS 2 NPs showed exceptional performance. The synthesized catalysts achieved a catalytic current density of 10 mA cm -2 at overpotentials as low as 300, 200 mV from oxygen, hydrogen evolution polarization curves through linear sweep voltammograms (LSVs). Furthermore, it has outstanding long-term durability under 10 mA cm -2 . The electrochemical performance was conducted with three electrode cell using 1.0 M KOH electrolyte and Pt counter electrode, and working electrode is ink type on Ni foam. Furthermore, MOF-driven CoS 2 was conducted through a full-cell test of overall water splitting for a practical two-electrode system in 1.0 M KOH. It exhibited an overpotential of 1.65 V at 10 mA cm -2 . We introduced MOFs to a new methodology based on thermodynamic processes. It showed the possibility of replacing noble metals such as Ir, Ru in terms of catalytic performance.
Type of Medium:
Online Resource
ISSN:
2151-2043
DOI:
10.1149/MA2020-01371579mtgabs
Language:
Unknown
Publisher:
The Electrochemical Society
Publication Date:
2020
detail.hit.zdb_id:
2438749-6
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