氫氣由於其零污染、零碳排、能量密度高等優點，氫能成為最為關注的新興能源之一。鹼性水電解是常見的氫氣製備方法，目前已有工業化實績，但在高電流密度下，由於氣泡生成後占據電極表面，以及溶液中的懸浮氣泡造成的溶液電阻上升，導致電解系統產生額外的能量損耗。而水電解反應後的氣相氫氣與氧氣混合，進入了氫氣的可燃範圍，對電解製程產生重大的安全疑慮，因此需在電解器中放置隔膜分離兩極之氣相產物，但隔膜的電阻亦會造成系統的額外能耗。
　　為了解決上述所提到的問題，本實驗在電解液中加入甘油，以甘油氧化反應取代產氧反應，使陽極產物由氣相改為液相，解決氣相產物混合之問題，並設計無隔膜矩形通道流反應器及氣液分離槽，通過壓力測試確認系統之氣密性，使得電化學反應在密閉系統中進行，利於氣相產物取樣分析。實驗時通過電解液循環流動，使反應生成氣泡易於結合及脫離，並隨電解液流動被帶至下游氣液分離槽中，施加強制對流後，亦可增加甘油質傳速率，提升系統電化學表現。
　　由於電解液流動狀態對質傳探討十分重要，我們使用染劑進行流體可視化，確認雷諾數與流體狀態之關係，結果顯示雷諾數在1250以內時，流態為層流，介於1250至2500時，進入過渡流態，當雷諾數大於2500後，流態呈現湍流。我們在不同流速下進行鹼性水電解實驗，並針對氣相產物進行取樣分析，實驗結果顯示隨著流速增加，改善氣泡對溶液電阻的影響，使電流表現微幅上升；而氣相產物分析後，氫氣與氧氣取樣結果與理論產量相符，依此驗證此系統之氣密性與取樣方法之合理性。
　　接著我們配置三種不同濃度的甘油鹼性水溶液進行反應，結果顯示當甘油濃度為0.05 m時，由於反應物甘油的消耗，導致電極表面甘油濃度不足，使甘油氧化與水氧化反應形成競爭反應，無法完全抑制氧氣的生成。此時依據氣相產物分析的結果，當施加2.4 V、2.8 V、3.2 V三個不同電壓時，水氧化反應在陽極電荷轉移中占比分別為51%、62%及71%，隨著電解液流率的上升，甘油質傳速率隨著強制對流而上升，使競爭反應得到改變，在陽極的電荷轉移中，甘油氧化反應的比例逐漸上升，造成氧氣產量下降，當系統雷諾數達到3000時，同樣在上述三個施加電位的反應中，水氧化反應在陽極電荷轉移中的占比分別降至27%、45%及53%，由此可見在施加強制對流流場後，對於增加甘油質傳速率及對競爭反應的影響。而在甘油濃度為2.1 m 以及12 m時，由於電極表面甘油濃度充足，產氧反應完全抑制，使得由於氣相產物混合而衍生的製程安全疑慮完全得到解決。

Hydrogen, due to its advantages of zero pollution, zero carbon emissions, and high energy density, has become one of the most popular emerging energy. Alkaline water electrolysis is a common method for hydrogen production, with industrial applications already in place. However, at high current densities, the generation of bubbles occupies the electrode surface, and the presence of suspended bubbles in the solution increases the electrical resistance of electrolyte, resulting in additional energy losses in the electrolysis system. Furthermore, the mixing of gaseous hydrogen and oxygen, the gas-phase products of water electrolysis, enter the flammable range of hydrogen, raising a significant safety risk to the electrolysis process. Therefore, it is necessary to incorporate a membrane in the electrolyzer to separate the gaseous products at the two electrodes. However, the membrane's resistance also contributes to additional energy consumption in the system.
To solve the aforementioned issues, the experiment added glycerol into the electrolyte to replace the oxygen evolution reaction(OER) with glycerol electrooxidation reaction(GEOR). This transformation converts the anodic products from gaseous to liquid phase, resolving the issue of mixing gaseous products. A membrane-free rectangular channel flow reactor and a gas-liquid separation tank were designed. Before start up, the system was confirmed through pneumatic pressure test, allowing the electrochemical reaction to occur within a closed system, with the sampling and analysis of the gaseous products. During the experiment, the electrolyte was circulated by metering pump to promote the coalescence and detachment of the generated bubbles, which were then carried downstream to the gas-liquid separator by the flow of the electrolyte. The application of forced convection also increased the glycerol mass transfer rate, thereby enhancing the electrochemical performance of the system.
Since the flow patterns of the electrolyte is crucial for transport phenomena, we employed dye visualization to observe the relationship between Reynolds number and fluid patterns. The results showed that at Reynolds numbers below 1250, the flow was laminar, transitioning flow regime between 1250 and 2500. Above a Reynolds number of 2500, the flow exhibited turbulence. We conducted alkaline water electrolysis experiments at different flow rates with the sampling and analysis of the gaseous byproducts. The experimental results showed that as the flow rate increased, the influence of bubbles on solution resistance was mitigated, resulting in a slight increase in current performance. After analyzing the gaseous products, the sampled results of hydrogen and oxygen matched the theoretical yields, thereby confirming the validity of the system design and sampling method.
Next, we conducted reactions using alkaline water solutions with three different glycerol concentrations. The results showed that When the glycerol concentration is 0.05 m, the consumption of glycerol as a reactant resulted in insufficient glycerol concentration at the electrode surface. This led to a competitive reaction between glycerol electrooxidation reaction and oxygen evolution reaction, making it difficult to completely suppress the production of oxygen. Based on the analysis of gaseous byproducts, the percentage of the oxygen evolution reaction in the anodic charge transfer was found to be 51%, 62%, and 71% when applying three different voltages of 2.4 V, 2.8 V, and 3.2 V, respectively. As the flow rate of the electrolyte increased, the glycerol mass transfer rate also increased due to forced convection, leading to a change in the competitive reactions. In the anodic charge transfer, the proportion of glycerol oxidation reaction gradually increased, resulting in a decrease in oxygen production. When the system Reynolds number reached 3000, the proportions of the oxygen evolution reaction in the anodic charge transfer decreased to 27%, 45%, and 53% for the three applied voltages mentioned above. This indicates the impact of forced convection in increasing the glycerol mass transfer rate and its effect on the competitive reactions. On the other hand, When the glycerol concentration is 2.1 m and 12 m, the electrode surface had sufficient glycerol concentration, leading to complete inhibition of the oxygen-producing reaction. Consequently, the safety concerns from the mixing of gaseous products were resolved.

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