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<p>The pristine β-MnO<sub>2</sub> (MO) and cobalt-doped β-MnO<sub>2</sub> (MCO_1 and MCO_2) were successfully prepared using a single-step hydrothermal technique. Powder X-ray diffraction studies confirm that the samples adopt tetragonal symmetry with a <i>P</i>4<sub>2</sub>/<i>mnm</i> (136) space group. Structural features, such as bond lengths, were obtained by performing Rietveld refinement on all the samples, which reveals the distorted nature (2 × 1.8175&#xa0;Å, 4 × 1.9346&#xa0;Å) of MnO<sub>6</sub> octahedra. FTIR studies on these samples revealed that the pristine β-MnO<sub>2</sub> displays well-defined absorption bands in the 400–900&#xa0;cm<sup>−1</sup> range, which become weakened and broadened upon cobalt doping, which is likely due to local structural distortions. The morphology studies of these samples revealed the presence of rod-like nanostructures with dimensions in the range of 1 – 1.5&#xa0;µm in length, and 120 – 250&#xa0;nm in diameter. EDX analysis confirms the presence of all the constituent elements in proportionate amounts, and elemental mapping further demonstrates the uniform spatial distribution throughout the sample. XPS analysis reveals the coexistence of Mn<sup>3+</sup>/Mn<sup>4+</sup> and oxygen vacancies in these samples. Electrochemical water oxidation measurements on these samples reveal that pristine β-MnO<sub>2</sub> exhibits a better overpotential (760&#xa0;mV at 10&#xa0;mA/cm<sup>2</sup>) compared to cobalt-doped samples MCO_1 (760&#xa0;mV) and MCO_2 (860&#xa0;mV). However, upon cycling, the activity of pristine β-MnO<sub>2</sub> and MCO_2 observed to improve while the MCO_1 sample degraded upon cycling. These studies provide insights into improving the long-term stability and enhancing the OER kinetics in Mn-based metal oxides.</p>

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Probing the structural and surface chemistry of cobalt-doped β-MnO2 for the alkaline oxygen evolution reaction

  • 期刊论文

  • 发表日期：

    2026年4月17日

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  • Matangi Chaitanya,
  • Seethiraju D. Ramarao

摘要

The pristine β-MnO2 (MO) and cobalt-doped β-MnO2 (MCO_1 and MCO_2) were successfully prepared using a single-step hydrothermal technique. Powder X-ray diffraction studies confirm that the samples adopt tetragonal symmetry with a P42/mnm (136) space group. Structural features, such as bond lengths, were obtained by performing Rietveld refinement on all the samples, which reveals the distorted nature (2 × 1.8175 Å, 4 × 1.9346 Å) of MnO6 octahedra. FTIR studies on these samples revealed that the pristine β-MnO2 displays well-defined absorption bands in the 400–900 cm−1 range, which become weakened and broadened upon cobalt doping, which is likely due to local structural distortions. The morphology studies of these samples revealed the presence of rod-like nanostructures with dimensions in the range of 1 – 1.5 µm in length, and 120 – 250 nm in diameter. EDX analysis confirms the presence of all the constituent elements in proportionate amounts, and elemental mapping further demonstrates the uniform spatial distribution throughout the sample. XPS analysis reveals the coexistence of Mn3+/Mn4+ and oxygen vacancies in these samples. Electrochemical water oxidation measurements on these samples reveal that pristine β-MnO2 exhibits a better overpotential (760 mV at 10 mA/cm2) compared to cobalt-doped samples MCO_1 (760 mV) and MCO_2 (860 mV). However, upon cycling, the activity of pristine β-MnO2 and MCO_2 observed to improve while the MCO_1 sample degraded upon cycling. These studies provide insights into improving the long-term stability and enhancing the OER kinetics in Mn-based metal oxides.