| 摘要: | 由於環境汙染與能源需求日益增加，發展可持續再生能源已成為當務之急。乙醇燃料電池(Direct ethanol fuel cell, DEFC)和甲酸燃料電池(Direct formic acid fuel cell, DFAFC)分別以其高能量密度和高電動力而受到廣泛關注。然而，在乙醇氧化反應(Ethanol oxidation reaction, EOR)和甲酸氧化反應(Formic acid oxidation reaction, FAOR)中，觸媒面臨著複雜的反應機制與中間體的產生，導致動力學反應緩慢和觸媒中毒，從而使觸媒失活。因此，開發高活性和高穩定性的觸媒至關重要。鈀(Palladium, Pd)因其在鹼性條件下表現出優異的陽極乙醇氧化反應性能，並在陽極甲酸反應中具有良好的表現，被視為有發展潛力的陽極反應觸媒。
在本研究中，通過油胺法(Oleylamine, OAm)合成了兩種不同比例的錫(Tin, Sn)修飾Pd/C觸媒，分別為Pd85-Sn15/C和Pd95-Sn5/C。研究Sn的修飾在乙醇氧化反應和甲酸氧化反應對於Pd/C觸媒之效應，並透過調整Sn的添加量達到最佳化。通過X光電子能譜儀(X-ray photoelectron spectroscopy, XPS)、X光吸收光譜(X-ray absorption spectroscopy, XAS) 和CO剝離測試(CO-stripping)，結果顯示Pd-Sn/C表面的Pd與SnO2之間的電子效應與鍵結有助於削弱Pd對中間體的吸附，表面的SnO2促進了中間體的氧化反應。同時，還觀察到微量添加Sn會暴露出更多Pd活性位點，從而促進了EOR和FAOR反應的進行。電化學結果表明，在鹼性電解質中，Pd-Sn/C展現出卓越的乙醇氧化性能，遠超過Pd/C(2131 mA/mgPd)。其中，Pd95-Sn5/C具有最佳的質量活性(MA)，達到6795 mA/mgPd。此外，Pd-Sn/C還展示出優異的穩定性，在經過2小時的計時電流(Chronoamperometric, CA)穩定性測試後，其中以Pd95-Sn5/C保持了最高的殘留活性，達到592 mA/mgPd。在酸性電解質中的甲酸氧化反應方面，Pd95-Sn5/C展現出最高的質量活性3381 mA/mgPd，並且經過2小時的計時電流穩定性測試後，Pd95-Sn5/C表現出最佳的穩定性。在乙醇氧化與甲醇氧化反應中，Pd95-Sn5/C的活性皆高於Pd85-Sn15/C，這進一步證實了微量錫的添加對改善催化性能的重要性。本研究提出了一種加入微量的Sn對Pd-Sn/C 觸媒進行改質，此方法顯著提高了Pd的利用率並提高了EOR和FAOR的性能和穩定性。
;The intensifying environmental pollution and growing energy demands have made it imperative to focus on the development of sustainable renewable energy sources. Direct ethanol fuel cell (DEFC) is highly regarded for their high energy density, while direct formic acid fuel cell (DFAFC) is known for their high-power density. However, complex reaction mechanisms on the catalyst surface and generation and poisoning of intermediates in the ethanol oxidation reaction (EOR) and formic acid oxidation reaction (FAOR), result in sluggish kinetics and deactivation. Therefore, the development of highly active and stable catalysts is of crucial importance. Palladium (Pd) is widely recognized as a highly promising catalyst for anode reactions, owing to its outstanding performance in the alkaline conditions of EOR and its favorable performance in the FAOR.
In this study, we used a simple oleylamine method to synthesize Pd-Sn/C catalysts, Pd85-Sn15/C and Pd95-Sn5/C, as the EOR and FAOR catalysts. We have investigated the effects of Sn modification on the performance of EOR and FAOR for Pd/C. Furthermore, by precisely controlling the amount of Sn added to Pd/C catalysts, their EOR and FAOR can be further optimized. X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XAS), and CO-stripping results revealed that the electronic interaction and bonding between Pd and Sn(O2) contributes to the weakening of the adsorption of intermediates on Pd. Furthermore, the presence of SnO2 on the catalyst surface enhances the oxidation of intermediates, thereby promoting the EOR and FAOR reactions. It also was observed that the addition of a small amount of Sn exposes more active sites of Pd, enhancing the electrochemical performance. Pd-Sn/C exhibits excellent EOR performance in alkaline solution, surpassing Pd/C (2131 mA/mgPd). Among them, Pd95-Sn5/C shows the best mass activity (MA) with a value of 6795 mA/mgPd. Furthermore, after a 2-hour chronoamperometric (CA) stability test, Pd-Sn/C exhibited remarkable stability compared to Pd/C (103 mA/mgPd), with Pd95-Sn5/C retaining the highest residual MA of 592 mA/mgPd. On the other hand, in FAOR, Pd95-Sn5/C demonstrates the highest MA of 3381 mA/mgPd in acid solution and maintains impressive stability even after a 2-hour CA stability test. The EOR and FAOR activities of Pd95-Sn5/C are both higher than those of Pd85-Sn15/C, further confirming the effect of adding trace amounts of Sn for improving electrochemical performance. This study proposes a modification of incorporating small amounts of Sn into Pd /C catalysts, which significantly enhances Pd utilization and improves the performance and stability of EOR and FAOR. |
