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<p>Designing efficient, cost-effective electrocatalysts for electrochemical splitting of water is essential towards developing clean hydrogen energy devices. Here, we report a set of NiS<sub>x</sub>@FeS<sub>x</sub> nanocomposites from NiFe-based Prussian Blue Analogue (PBA) materials, along with a detailed analysis of how sulfurization temperature in a range of 400–650&#xa0;°C impacts structure evolution, surface composition, and electrochemical performance. The structure determination of NiS<sub>x</sub>@FeS<sub>x</sub> nanocomposites confirmed mixed-metal sulfide phases of NiS<sub>2</sub> as well as FeS<sub>2</sub>, along with heterogeneous interfaces and favorable Ni<sup>3</sup>⁺ and Fe<sup>3</sup>⁺ oxidation states, both of which are significant for catalytic activity. Amongst all, NiS<sub>x</sub>@FeS<sub>x</sub> nanocomposite sulfurized at 500&#xa0;°C displayed maximal electrocatalytic performance. Its higher catalytic activity was attributed to a synergistic coupling of heterogeneous, interconnected interfaces along with increased ionic conductivity, allowing for more effective charge transfer as well as enhanced reaction kinetics. The electrochemical data affirmed that NiS<sub>x</sub>@FeS<sub>x</sub>-500 needed a low overpotential of 276&#xa0;mV towards oxygen evolution reaction (OER) at 50&#xa0;mA&#xa0;cm⁻<sup>2</sup>, coupled with a resultant Tafel slope of 91&#xa0;mV dec⁻<sup>1</sup>. Towards hydrogen evolution reaction (HER), it demonstrated a low overpotential of 179&#xa0;mV at 10&#xa0;mA&#xa0;cm⁻<sup>2</sup> as well as a Tafel slope of 81&#xa0;mV dec⁻<sup>1</sup>, reflecting effective reaction kinetics. Additionally, the two-electrode electrolyzer constructed using this material both as anode and cathode needed merely 1.706&#xa0;V to reach 10&#xa0;mA&#xa0;cm⁻<sup>2</sup>, while operating stably over a period of 10&#xa0;h. These observations point towards potential applications of NiFe-PBA-derived NiS<sub>x</sub>@FeS<sub>x</sub>-500 nano composite as a stable, cost-effective bifunctional electrocatalyst towards overall water splitting technologies.</p> Graphical abstract <p></p>

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Tailoring sulfurization conditions in NiFe-PBA-derived NiSx@FeSx electrocatalysts for enhanced bifunctional water splitting

  • 期刊论文

  • 发表日期：

    2025年9月20日

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  • Purusottam Reddy B,
  • Shrouq H. Aleithan,
  • Naveen B,
  • Youngsuk Suh,
  • Si-Hyun Park

摘要

Designing efficient, cost-effective electrocatalysts for electrochemical splitting of water is essential towards developing clean hydrogen energy devices. Here, we report a set of NiSx@FeSx nanocomposites from NiFe-based Prussian Blue Analogue (PBA) materials, along with a detailed analysis of how sulfurization temperature in a range of 400–650 °C impacts structure evolution, surface composition, and electrochemical performance. The structure determination of NiSx@FeSx nanocomposites confirmed mixed-metal sulfide phases of NiS2 as well as FeS2, along with heterogeneous interfaces and favorable Ni3⁺ and Fe3⁺ oxidation states, both of which are significant for catalytic activity. Amongst all, NiSx@FeSx nanocomposite sulfurized at 500 °C displayed maximal electrocatalytic performance. Its higher catalytic activity was attributed to a synergistic coupling of heterogeneous, interconnected interfaces along with increased ionic conductivity, allowing for more effective charge transfer as well as enhanced reaction kinetics. The electrochemical data affirmed that NiSx@FeSx-500 needed a low overpotential of 276 mV towards oxygen evolution reaction (OER) at 50 mA cm⁻2, coupled with a resultant Tafel slope of 91 mV dec⁻1. Towards hydrogen evolution reaction (HER), it demonstrated a low overpotential of 179 mV at 10 mA cm⁻2 as well as a Tafel slope of 81 mV dec⁻1, reflecting effective reaction kinetics. Additionally, the two-electrode electrolyzer constructed using this material both as anode and cathode needed merely 1.706 V to reach 10 mA cm⁻2, while operating stably over a period of 10 h. These observations point towards potential applications of NiFe-PBA-derived NiSx@FeSx-500 nano composite as a stable, cost-effective bifunctional electrocatalyst towards overall water splitting technologies.

Graphical abstract