Deciphering the Dynamic Structure Evolution of Fe- and Ni-Codoped CoS₂ for Enhanced Water Oxidation

Abstract

Multimetal doping is a promising strategy to achieve high-performance electrocatalysts for the oxygen evolution reaction (OER) due to synergistic effects; however, understanding the dynamic structure evolution and clarifying the catalytic mechanism of each individual doping metal in multimetal-based electrocatalysts remain elusive. Here, we report the synthesis of homogeneous single-metal and bimetal doping sulfides with a pyrite structure for OER catalysts via a high-pressure and high-temperature (HPHT) technique; operando Raman and X-ray absorption spectroscopy (XAS) studies are performed to capture the dynamic evolution during the OER process. Our results find that an Fe- and Ni-codoped CoS2 electrocatalyst exhibits significantly improved OER activity with an overpotential of 242 (295) mV at 10 (100) mA cm–2 and robust stability over 500 h in an alkaline medium. Operando analysis reveals that Fe and Ni incorporations not only expedite the dynamic response of self-reconstructions of the Fe,Ni-CoS2 surface but also accelerate the oxidation of Co and Fe into high-valence oxyhydroxides while suppressing nickel oxidation to form Ni­(OH)2 for optimized activity and robust stability. This finding provides a fundamental understanding of the composition design, dynamic reaction pathways, and controlling principle for highly active multimetal-based OER catalysts.

Simultaneous optimization of CoIr alloy nanoparticles and 2D graphitic-N doped carbon support in CoIr@CN by Ir doping for enhanced oxygen and hydrogen evolution reactions

“…And the weak peaks belonging to CoOOH emerge from 1.3 V at around 504, 513, and 596 cm −1 , revealing a partial transformation from hydroxides to oxyhydroxides species. 55–57 Therefore, the new phases of hydroxides and oxyhydroxides are generated on the surface of CoIr@CN-0.20 during the OER process, in which the oxyhydroxide species could contribute to the superb catalytic performance. 55,57…”

“…55–57 Therefore, the new phases of hydroxides and oxyhydroxides are generated on the surface of CoIr@CN-0.20 during the OER process, in which the oxyhydroxide species could contribute to the superb catalytic performance. 55,57…”

“…And the weak peaks belonging to CoOOH emerge from 1.3 V at around 504, 513, and 596 cm À1 , revealing a partial transformation from hydroxides to oxyhydroxides species. [55][56][57] Therefore, the new phases of hydroxides and oxyhydroxides are generated on the surface of CoIr@CN-0.20 during the OER process, in which the oxyhydroxide species could contribute to the superb catalytic performance. 55,57 To further reveal the microstructure and composition transformation of CoIr@CN-0.20 during the OER process, the aer-OER CoIr@CN-0.20 catalyst was probed by XRD, SEM, TEM, and XPS.…”

“…[55][56][57] Therefore, the new phases of hydroxides and oxyhydroxides are generated on the surface of CoIr@CN-0.20 during the OER process, in which the oxyhydroxide species could contribute to the superb catalytic performance. 55,57 To further reveal the microstructure and composition transformation of CoIr@CN-0.20 during the OER process, the aer-OER CoIr@CN-0.20 catalyst was probed by XRD, SEM, TEM, and XPS. Aer a long-term OER electrocatalytic process, the XRD pattern of CoIr@CN-0.20 shows a weaker reection of the metallic Co phase and no additional new peaks, indicating that some crystalline Co remains and a new oxidic amorphous phase has formed (Fig.…”

In situ synthesis of morphology-controlled MoOx/Fe1−xS bifunctional catalysts for high-efficiency and stable alkaline water splitting

“…The bimetallic doping not only accelerated the dynamic response of the catalyst surface self-reconfiguration but also accelerated the oxidation of cobalt and iron to higher valence hydroxides, which improved the activity and stability. Fe, Ni-CoS 2 had an overpotential of 242 (295) mV at 10 (100) mA cm −2 in alkaline medium and was stable for more than 500 h. 17 Shen et al designed bifunctional trimetallic catalysts by controlling the composition, ratio, and structure of the elements. Spherical Co 3 S 4 and Ni-Fe sulfide porous nanosheet array catalysts (NiFeCoS x @FeNi 3 ) grown vertically on FeNi 3 foam were driven by 10 mA cm −2 for the HER and OER in 1 M KOH solution with overpotentials of 88 mV and 210 mV, respectively.…”