| 摘要: | 氫氣具高能量密度且零碳排放特性，為極具潛力的未來能源載體，而電化學水分解結合再生能源，被廣泛認為是生產綠氫的關鍵途徑。質子交換膜水電解(proton exchange membrane water electrolysis, PEMWE)具有高電流密度、高氫氣純度及快速響應等優勢。然而，其廣泛應用仍受制於對白金(Pt)觸媒的高度依賴。Pt的高成本與耐久性限制了PEM大規模部署，因此迫切需要開發低Pt用量且性能穩定的觸媒。
本研究設計了應用於酸性(0.5 M H2SO4)環境中的析氫反應(hydrogen evolution reaction, HER)電催化觸媒，利用沸石咪唑骨架(zeolitic imidazolate framework, ZIF)衍生多孔碳載體結合微量Co/NC負載成功製備了低負載Pt基電催化觸媒。ZIF-67衍生的多孔碳框架提供了開放通道結構，因其結構可有效限制Pt奈米粒子的團聚，同時提升活性位點暴露度並抑制結構劣化。再者，策略性調控Co-N-C位點可作為Pt的錨定中心，能
其分散負載並有效抑制Pt在反應過程中的溶解，結合上述同步提升催化活性、金屬利用率及穩定性。值得注意的是，Pt-Co/NC在酸性環境中表現卓越，在電流密度10 mA cm-2 下的過電位(η10)僅為6 mV，Tafel斜率為11 mV dec-1，質量活性高達3054 A g-1。為深入探討觸媒催化機制，進行了臨場X光吸收光譜(X-ray absorption spectroscopy, XAS)分析，剖析HER過程中Pt配位環境的變遷，同時利用電感耦合電漿發射光譜(inductively coupled plasma optical emission spectrometry, ICP-OES)分析穩定性測試後 Pt 的溶解程度。臨場XAS與ICP-OES結果顯示，ZIF-67衍生的多孔碳載體及Co-N-C錨定位點的協同效應，提供良好的結構穩定性，也有效抑制了Pt的團聚與溶解。在實際應用評估中，將
該觸媒當作陰極在PEMWE系統中進行測試，於1.72 V下達到1.0 A cm-2的電流密度，並在1 A cm-2下穩定運行超過20小時，凸顯其卓越的實際應用潛力。綜合以上，本研究為開發高活性與耐久性的低Pt負載HER觸媒設計提供了重要解方。;Hydrogen, featuring high energy density and carbon-free utilization, is widely regarded as a promising energy carrier for future sustainable energy systems. Among various hydrogen production technologies, electrochemical water splitting powered by renewable electricity has emerged as a key pathway for the generation of green hydrogen. Proton exchange membrane water electrolysis (PEMWE) offers advantages, including high current density, high hydrogen purity, and rapid dynamic response. However, its large-scale deployment remains severely constrained by the heavy reliance on platinum (Pt) electrocatalysts. The high cost and durability concerns associated with Pt necessitate the development of electrocatalysts with reduced Pt content while maintaining high activity and long-term stability.
In this study, a low-Pt-loading electrocatalyst for the hydrogen evolution reaction (HER) in acidic media (0.5 M H2SO4) was designed by integrating a zeolitic imidazolate framework (ZIF) derived porous carbon support with low Co/NC loading. The porous carbon framework provides an open-channel architecture that effectively confines Pt nanoparticles, thereby suppressing aggregation, enhancing active site exposure, and mitigating structural degradation during operation. Moreover, the strategic modulation of Co-N-C sites serves as anchoring centers for Pt, promoting uniform dispersion and effectively suppressing the dissolution of Pt during HER. This synergistic design simultaneously enhances catalytic activity, Pt utilization efficiency, and structural stability.
Notably, the Pt-Co/NC exhibits outstanding HER performance under acidic conditions, delivering an ultralow overpotential of only 6 mV at 10 mA cm-2 (η10), a small Tafel slope of 11 mV dec-1, and an exceptionally high mass activity of 3054 A g-1. To gain deeper insights into the catalytic mechanism, in-situ X-ray absorption spectroscopy (XAS) was conducted to elucidate the dynamic evolution of coordination environments of Pt during HER, while inductively coupled plasma optical emission spectrometry (ICP-OES) was employed to quantify the degree of Pt dissolution after durability tests. The combined in-situ XAS and ICP-OES results reveal that the synergistic effects of the ZIF-67-derived porous carbon support and Co-N-C anchoring sites provide excellent structural stability, effectively suppressing Pt aggregation and dissolution.
For practical evaluation, the Pt-Co/NC was further employed as the cathode in a PEMWE device. The electrolyzer achieves a current density of 1.0 A cm-2 at a cell voltage of 1.72 V and maintains stable operation for over 20 h at 1 A cm-2, demonstrating its practical applicability. Overall, this work provides an effective strategy for the rational design of highly active and durable low-Pt loading HER electrocatalysts. |
