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<p>While nickel-iron metal-organic frameworks (NiFe MOFs) featuring Lewis acid sites have been extensively employed as efficient oxygen evolution reaction (OER) electrocatalysts, the role of Brønsted acidity remains markedly underexplored. Herein, the electron-modulating nitro (–NO<sub>2</sub>) and amino (–NH<sub>2</sub>) groups were introduced into MIL-88B (NiFe) to systematically tune Brønsted acidity and thus regulate OER performance. Notably,–NH<sub>2</sub> functionalized MIL-88B (FeNi) with elevated Brønsted acidity shows both enhanced OER activity and stability, whereas–NO<sub>2</sub> incorporation conversely compromised electrocatalytic performance. The results reveal that high Brønsted acidity modulates the electronic structure of metal sites with enhanced OH<sup>−</sup> adsorption efficiency, which accelerates the electrochemical surface reconstruction for promoting OER activity. Concurrently, the superior stability originates from intensified metal-oxygen bonds to inhibit the dissolution of Fe species. Consequently,–NH<sub>2</sub>-functionalized MIL-88B (NiFe) achieves a markedly reduced overpotential of 37 and 69 mV at 10 mA cm<sup>−2</sup> relative to unfunctionalized and–NO<sub>2</sub>-modified counterparts, respectively. The catalyst also maintains stability with minimal activity decay during chronoamperometry tests for 100 h. When deployed in an anion exchange membrane water electrolyzer as anode, the–NH<sub>2</sub>-functionalized MIL-88B (FeNi) demonstrates exceptional durability (450 h) with negligible activity decay (0.363 mV h<sup>−1</sup> at 1.0 A cm<sup>−2</sup>, 60 °C). This work establishes ligand functionalization as a powerful strategy for Brønsted acidity regulation and elucidates its critical role in enhancing OER performance.</p>

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Ligand engineering mediated Brønsted acidity of nickel-iron metal-organic frameworks toward efficient oxygen evolution reaction

  • 期刊论文

  • 发表日期：

    2026年3月16日

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  • Zhaoyang Wang,
  • Heng Liu,
  • Hanxiao Liao,
  • Chengxiong Wang,
  • Kejun Chen,
  • Xin Wang,
  • Jiaxin Tong,
  • Pengfei Tan,
  • Hao Cui,
  • Jun Pan

摘要

While nickel-iron metal-organic frameworks (NiFe MOFs) featuring Lewis acid sites have been extensively employed as efficient oxygen evolution reaction (OER) electrocatalysts, the role of Brønsted acidity remains markedly underexplored. Herein, the electron-modulating nitro (–NO2) and amino (–NH2) groups were introduced into MIL-88B (NiFe) to systematically tune Brønsted acidity and thus regulate OER performance. Notably,–NH2 functionalized MIL-88B (FeNi) with elevated Brønsted acidity shows both enhanced OER activity and stability, whereas–NO2 incorporation conversely compromised electrocatalytic performance. The results reveal that high Brønsted acidity modulates the electronic structure of metal sites with enhanced OH− adsorption efficiency, which accelerates the electrochemical surface reconstruction for promoting OER activity. Concurrently, the superior stability originates from intensified metal-oxygen bonds to inhibit the dissolution of Fe species. Consequently,–NH2-functionalized MIL-88B (NiFe) achieves a markedly reduced overpotential of 37 and 69 mV at 10 mA cm−2 relative to unfunctionalized and–NO2-modified counterparts, respectively. The catalyst also maintains stability with minimal activity decay during chronoamperometry tests for 100 h. When deployed in an anion exchange membrane water electrolyzer as anode, the–NH2-functionalized MIL-88B (FeNi) demonstrates exceptional durability (450 h) with negligible activity decay (0.363 mV h−1 at 1.0 A cm−2, 60 °C). This work establishes ligand functionalization as a powerful strategy for Brønsted acidity regulation and elucidates its critical role in enhancing OER performance.