Research on the hydrogen storage performance of g-C3N4 nanotubes after microwave irradiation

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Title:	Research on the hydrogen storage performance of g-C3N4 nanotubes after microwave irradiation
Authors:	施詠馨;Yung-Hsin, SHIH
Contributors:	化學工程與材料工程學系
Keywords:	儲氫;石墨氮化碳（g-C3N4）;微波輻射;白內障運動模式;原子級損傷機制;hydrogen storage;graphitic carbon nitride (g-C3N4);microwave irradiation;cataracting motion mode;atomic-level damage mechanisms
Date:	2024-08-07
Issue Date:	2024-10-09 15:27:25 (UTC+8)
Publisher:	國立中央大學
Abstract:	摘要考慮到與傳統儲氫系統相關的安全性和成本問題，本研究旨在探索使用石墨氮化碳（g-C3N4）奈米管作為儲氫材料。 g-C3N4 奈米管因其獨特的性質（例如豐富的活性邊緣、輕質結構以及高氫充放電速率）而成為有前途的候選材料。本研究重點研究微波輻照處理後球磨 g-C3N4 奈米管的儲氫性能。目的是在微波輻射過程中在管壁上引入缺陷和孔洞，從而增強氫的吸附。如先前的研究所示，樣本經過球磨，球填充率為 4.4% 和 10%，確保充分混合。然後將球磨的樣品進行微波輻射，以研究暴露時間和材料形態對微波吸收和隨後的儲氫能力的影響。微波輻射處理以中等功率等級(350-500W)進行，持續時間為4分鐘和8分鐘。值得注意的是，BET 分析表明，10% 球填充率的樣品在微波照射 4 分鐘後表現出最佳的微孔生成（2 至 7 nm）。拉曼光譜還表明，照射 4 分鐘後 D 帶發生顯著變化，表明 g-C3N4 結構內形成了缺陷。這些微孔對於增強氫氣進入管道至關重要，從而改善氫氣儲存。使用 Sievert 方法進行的儲氫測試證實，10% 球填充率的樣品優於 4.4% 的樣品，表現出更穩健的簇狀形態和優異的微波吸收特性。這導致更有效的微孔形成並改善儲氫性能。對於10%球填充率的樣品，在3.7 MPa氫氣壓力下微波照射4分鐘後，儲氫能力從0.036 wt.%增加到0.071 wt.%。然而，長時間的照射（8分鐘）會導緻小孔和管狀結構的破壞，形成較大的孔（> 50 nm）並減少表面積。這種效應在 4.4% 球填充率樣本中尤其明顯，在照射 8 分鐘後顯示最低的儲氫容量 (0.0225 wt.%)。儲氫性能的改善歸因於4分鐘微波處理過程中缺陷的產生、孔結構的改變和表面功能化。然而，較長的照射時間（8 分鐘）會對材料結構產生不利影響，這可能是由於焊接和聚結等原子級損傷機製造成的。這項研究表明，精確控制球磨參數和微波輻射持續時間對於優化 g-C3N4 奈米管的儲氫能力至關重要。結果表明，精心調整的微波處理可以顯著提高這些材料在儲氫應用中的性能。關鍵字：儲氫，石墨氮化碳（g-C3N4），微波輻射，白內障運動模式，原子級損傷機制。 ;Given the safety and cost issues associated with traditional hydrogen storage systems, this study aims to explore the use of graphitic carbon nitride (g-C3N4) nanotubes as a hydrogen storage material. g-C3N4 nanotubes have emerged as promising candidates due to their unique properties, such as abundant active edges, lightweight structure, and high hydrogen charging and discharging rates. This study focuses on investigating the hydrogen storage properties of ball-milled g-C3N4 nanotubes after microwave irradiation treatment. The aim is to introduce defects and holes in the tube walls during the microwave irradiation process, thereby enhancing hydrogen adsorption. The samples were ball-milled with ball filling rate of 4.4% and 10%, ensuring thorough mixing, as demonstrated in previous studies. The ball-milled samples were then subjected to microwave irradiation to study the effects of exposure time and material morphology on microwave absorption and subsequent hydrogen storage capabilities. Microwave irradiation treatments were conducted at moderate power levels (350-500 W) for durations of 4 and 8 minutes. Notably, the BET analysis showed that the 10% ball filling rate sample exhibited optimal micropore generation (2 to 7 nm) after 4 minutes of microwave irradiation. Raman spectroscopy also indicated significant changes in the D band after 4 minutes of irradiation, suggesting the formation of defects within the g-C3N4 structure. These micropores are crucial for enhancing hydrogen ingress into the tubes, thereby improving hydrogen storage. Hydrogen storage tests using Sievert′s method confirmed that the 10% ball filling rate sample outperformed the 4.4% sample, exhibiting a more robust cluster-like morphology and superior microwave absorption characteristics. This led to more efficient micropore formation and improved hydrogen storage performance. For the 10% ball filling rate sample, the hydrogen storage capacity increased from 0.036 wt.% to 0.071 wt.% after 4 minutes of microwave irradiation at 3.7 MPa hydrogen pressure. However, prolonged irradiation (8 minutes) resulted in the destruction of small pores and tubular structures, forming larger pores (>50 nm) and reducing surface area. This effect was especially pronounced in the 4.4% ball filling rate samples, which showed the lowest hydrogen storage capacity (0.0225 wt.%) after 8 minutes of irradiation. The improvement in hydrogen storage performance is attributed to the generation of defects, pore structure modification, and surface functionalization during the 4-minute microwave treatment. However, longer irradiation times (8 minutes) had detrimental effects on the material structure, likely due to atomic-level damage mechanisms such as welding and coalescence. This study demonstrates the critical importance of precise control over ball milling parameters and microwave irradiation duration in optimizing the hydrogen storage capabilities of g-C3N4 nanotubes. The results suggest that carefully tuned microwave treatments can significantly enhance the performance of these materials in hydrogen storage applications.
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