OH-Functionalized N-Doped Graphene Quantum Dots as an Efficient Metal-Free Catalysts for Oxygen Reduction Reaction in PEMFCs

IF 2.7 4区化学 Q3 CHEMISTRY, PHYSICAL

Electrocatalysis Pub Date : 2024-04-09 DOI:10.1007/s12678-024-00869-8

Thangaraj Thiruppathiraja, Senthilkumar Lakshmipathi

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Abstract

Utilizing the density functional theory (DFT) method, we investigated the catalytic activity of N-doped graphene quantum dots (NGQDs) with nitrogen (N) atoms strategically doped at various active sites on the surface. We focused on exploring their efficiency in the 2e⁻ and 4e⁻ reduction pathways for oxygen reduction reaction (ORR). By introducing N-doping at the central benzene ring of carbon-based materials, we observed the formation of localized π-orbitals, significantly enhancing their electrocatalytic activity. In comparison to other reported catalysts, our N-doped GQD metal-free electrocatalyst displayed remarkable adsorption capability. Furthermore, we introduced the hydroxyl group (OH) into the functionalized N-doped GQDs, which further improved electrocatalytic performance. This enhancement was attributed to the decreased HOMO–LUMO energy gap and increased chemical reactivity. The calculated free energy (ΔG) values for each elementary reaction step in the 4e⁻ reduction pathway were highly favorable and indicated the feasibility of the process. Our findings indicate that N-doped GQDs exhibit exceptional activity for the ORR, positioning them as promising carbon-based metal-free electrocatalysts. Consequently, they hold significant potential as an alternative to noble metal-based catalysts in proton exchange membrane fuel cells (PEMFCs) and metal-air batteries.

Graphical Abstract

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羟基官能化 N 掺杂石墨烯量子点作为 PEMFC 中氧还原反应的高效无金属催化剂

利用密度泛函理论（DFT）方法，我们研究了掺杂氮原子的石墨烯量子点（NGQDs）的催化活性，氮原子被策略性地掺杂在表面的不同活性位点上。我们重点探索了它们在氧还原反应（ORR）的 2e- 和 4e- 还原途径中的效率。通过在碳基材料的中心苯环上引入 N 掺杂，我们观察到局部 π 轨道的形成，从而显著提高了它们的电催化活性。与其他已报道的催化剂相比，我们的 N 掺杂 GQD 无金属电催化剂具有显著的吸附能力。此外，我们在功能化 N 掺杂 GQD 中引入了羟基（OH），从而进一步提高了电催化活性。这种提高归因于 HOMO-LUMO 能隙的减小和化学反应活性的提高。计算得出的 4e 还原途径中每个基本反应步骤的自由能 (ΔG)值都非常有利，表明了该过程的可行性。我们的研究结果表明，掺杂 N 的 GQDs 在 ORR 中表现出卓越的活性，使其成为前景广阔的碳基无金属电催化剂。因此，在质子交换膜燃料电池（PEMFC）和金属-空气电池中，它们具有替代贵金属催化剂的巨大潜力。

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来源期刊

Electrocatalysis CHEMISTRY, PHYSICAL-ELECTROCHEMISTRY

CiteScore

4.80

自引率

6.50%

发文量

审稿时长

>12 weeks

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