Regulating Oxygen Vacancy Concentration Activates Inert 2D Bi₂O₃ Nanosheets for Efficient HER

Regulating Oxygen Vacancy Concentration Activates Inert 2D Bi₂O₃ Nanosheets for Efficient HER

The oxygen vacancy (Vo) is closely related to the activity of hydrogen evolution reaction (HER) in electrocatalysts. However, the role of vacancy defects and their concentration effects remain unclear. Here, we selected Bi₂O₃ as a model, which is an unfavorable electrocatalyst for HER due to its non-ideal Gibbs free energy of hydrogen adsorption (ΔGₕ), to explore the impact of Vo on HER performance.
By employing a simple plasma irradiation strategy, we prepared Bi₂O₃ nanosheets with varying Vo concentrations to evaluate the impact of defects on the HER process. Surprisingly, while the generated oxygen vacancies contribute to enhancing HER performance, HER activity significantly decreases when the Vo concentration exceeds a certain saturation point.
By adjusting the treatment time to modulate the Vo concentration in Bi₂O₃ nanosheets, we obtained a Bi₂O₃ catalyst with optimal oxygen vacancy concentration and detectable charge carrier concentration (1.52 × 10²⁴ cm⁻³). This catalyst exhibited enhanced HER performance in alkaline solution, achieving an overpotential of 174.2 mV at 10 mA cm⁻², a Tafel slope of 80 mV dec⁻¹, and an exchange current density of 316 mA cm⁻², which is close to top-tier activity among Bi-based HER electrocatalysts.
Density functional theory calculations confirmed the relationship between H preferential adsorption on Bi₂O₃ and the oxidative chemical potential (ΔμO) and oxygen partial pressure (PO₂), revealing that high Vo concentration leads to excessive stability of adsorbed hydrogen, thereby reducing HER activity.
This study reveals the relationship between oxygen vacancy concentration and HER catalytic activity, providing insights into activating inert catalytic materials into efficient electrocatalysts.

Regulating Oxygen Vacancy Concentration Activates Inert 2D Bi₂O₃ Nanosheets for Efficient HER01 Research Background and Motivation

Application of 2D Materials in HER: Due to their unique physicochemical properties, 2D materials exhibit great potential in electrochemical hydrogen evolution reactions.

Catalytic Inertia of Bismuth Oxide: Although bismuth oxide (Bi₂O₃) is an important semiconductor material widely used in photocatalysis and electrocatalysis, its catalytic inertia limits its direct application in electrochemical hydrogen evolution reactions.

Role of Oxygen Vacancies: As a type of defect in materials, oxygen vacancies can modulate the electronic structure and catalytic performance of materials, providing a possibility to transform inert bismuth oxide into efficient HER catalysts.

Regulating Oxygen Vacancy Concentration Activates Inert 2D Bi₂O₃ Nanosheets for Efficient HER

02 Research Methods

Material Preparation: Bi₂O₃ nanosheets with different oxygen vacancy concentrations were prepared using specific synthesis methods.

Characterization Techniques: The crystal structure, morphology, and thickness of the materials were analyzed in detail using characterization techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and atomic force microscopy (AFM).

Electrochemical Performance Testing: The HER catalytic performance of the materials was evaluated using electrochemical performance testing methods such as linear sweep voltammetry (LSV), Tafel slope testing, and electrochemical impedance spectroscopy (EIS).

03 Modulating Oxygen Vacancy Concentration

Modulation Method: By changing the synthesis conditions (such as temperature, time, atmosphere, etc.), precise modulation of the oxygen vacancy concentration in the 2D bismuth oxide nanosheets was achieved.

Modulation Effects: With the increase of oxygen vacancy concentration, the electronic structure of the material changes,leading to enhanced conductivity and significantly improved HER catalytic activity.

Optimal Oxygen Vacancy Concentration: The study found that there exists an optimal range of oxygen vacancy concentration that allows the material’s HER catalytic performance to reach its best.

04 Visual Guide

Regulating Oxygen Vacancy Concentration Activates Inert 2D Bi₂O₃ Nanosheets for Efficient HER

Regulating Oxygen Vacancy Concentration Activates Inert 2D Bi₂O₃ Nanosheets for Efficient HER

Regulating Oxygen Vacancy Concentration Activates Inert 2D Bi₂O₃ Nanosheets for Efficient HER

Regulating Oxygen Vacancy Concentration Activates Inert 2D Bi₂O₃ Nanosheets for Efficient HER

Regulating Oxygen Vacancy Concentration Activates Inert 2D Bi₂O₃ Nanosheets for Efficient HER

Regulating Oxygen Vacancy Concentration Activates Inert 2D Bi₂O₃ Nanosheets for Efficient HER

Regulating Oxygen Vacancy Concentration Activates Inert 2D Bi₂O₃ Nanosheets for Efficient HER

05 Discussion on Catalytic Mechanism

Active Sites: Oxygen vacancies serve as active sites that can adsorb and activate hydrogen ions, reducing the activation energy for HER.

Electron Transport: The introduction of oxygen vacancies improves the electron transport properties of the material, facilitating rapid charge transfer and increasing reaction rates.

Synergistic Effects: Oxygen vacancies work synergistically with other structural features of the material’s surface (such as edge effects, defects, etc.),further enhancing HER catalytic performance.

06 Performance Evaluation and Comparison

HER Catalytic Performance: By comparing the HER catalytic performance of 2D bismuth oxide nanosheets with different oxygen vacancy concentrations, it was found that materials with optimal oxygen vacancy concentrations exhibited the lowest onset potential, highest current density, and smallest Tafel slope.

Stability Testing: After prolonged electrochemical testing, materials with optimal oxygen vacancy concentrations demonstrated good stability, with no significant degradation in catalytic performance.

Comparison with Other Catalysts: The catalysts prepared in this study were compared with other reported HER catalysts, showing certain advantages in catalytic performance.

07 Practical Application Prospects

Clean Energy: 2D bismuth oxide nanosheets, as efficient HER catalysts, have broad application prospects in clean energy fields such as hydrogen energy.

Electrolysis of Water for Hydrogen Production: In the process of water electrolysis for hydrogen production, this catalyst can significantly increase the yield and efficiency of hydrogen production, reducing production costs.

Catalyst Design: This study provides new ideas and methods for designing other efficient and stable HER catalysts.

08 Conclusion and Outlook

Research Conclusion: By modulating oxygen vacancy concentrations, we successfully transformed the inert 2D bismuth oxide nanosheets into efficient HER catalysts, achieving significant improvements in catalytic performance.

Future Outlook: Further research will focus on the synergistic mechanisms between oxygen vacancies and other structural features, as well as how to produce HER catalysts with better performance through more precise control methods.

09 Summary

  • By precisely controlling the concentration of oxygen vacancies, the HER performance of originally inert Bi₂O₃ nanosheets can be significantly enhanced.This research not only experimentally verifies this but also theoretically explains the mechanisms by which oxygen vacancy concentrations affect HER activity.

  • This finding provides new ideas and methods for designing more efficient and stable electrocatalysts, which is of great significance for promoting the development of clean energy technologies such as hydrogen energy.At the same time, this study also demonstrates the potential of plasma irradiation strategies in material modification, providing beneficial references for optimizing the performance of other 2D or nanomaterials.

  • This research successfully achieved the conversion of inert 2D bismuth oxide nanosheets into efficient electrocatalysts for electrochemical hydrogen evolution reactions through the modulation of oxygen vacancy concentrations.

Through detailed characterization and electrochemical performance testing, the mechanisms by which oxygen vacancy concentrations influence the catalytic performance of materials were revealed. This catalyst has broad application prospects in clean energy fields such as hydrogen energy, providing new ideas and methods for future catalyst design. At the same time, this study also offers valuable insights and references for optimizing the catalytic performance of other 2D materials.

▲ Video of Disk Electrode Spin Coater Operation

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