Ultra-low voltage bipolar hydrogen production from biomass-derived aldehydes and water in membrane-less electrolyzers
Ultra-low voltage bipolar hydrogen production from biomass-derived aldehydes and water in membrane-less electrolyzers
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DOI：
10.1039/d2ee01427k
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发表时间：
2022-08-12
影响因子：
32.5
通讯作者：
Li, Wenzhen
中科院分区：
文献类型：
--
作者：
Liu, Hengzhou;Agrawal, Naveen;Li, Wenzhen
使用可再生能源进行水电解作为制氢的绿色途径正在被积极探索。然而，由于阳极析氧反应 (OER) 缓慢，且 H-2 和 O-2 混合相关的安全问题，它受到高能耗的限制。在这里，我们用醛的电催化氧化脱氢 (EOD) 取代了 OER，用于双极 H-2 生产，并在比水电解期间低得多的电池电压下实现了工业级电流密度。实验和计算研究表明，铜表面上的 C-H 解离存在合理的障碍，主要通过二醇中间体，与溶液相坎尼扎罗反应存在潜在的依赖竞争。使用电置换法制备的多孔 CuAg 催化剂进一步增强了 EOD 反应的动力学。通过Ag的掺入及其在Cu表面的修饰，几何电流密度和电催化剂的耐久性得到显着提高。最后，我们在基于膜电极组件的流通池中设计了双极 H-2 生产系统，以促进质量传输，在 0.4 V 和 0.6 V 的池电压下分别实现 248 和 390 mA cm(-2) 的最大电流密度。阴极和阳极反应产生的 H-2 的法拉第效率均接近 100%。利用双极性 H-2 生产，避免与 H-2/O-2 混合相关的问题，一种廉价、易于制造的透析多孔膜被证明可以替代昂贵的阴离子交换膜，在简单的反应器中实现节能且经济高效的 H-2 生产过程。根据初步技术经济评估，H-2 的估计价格为 2.51 美元/公斤，与美国能源部的“绿色 H-2”目标相比具有竞争力。
Water electrolysis using renewable energy inputs is being actively pursued as a green route for hydrogen production. However, it is limited by the high energy consumption due to the sluggish anodic oxygen evolution reaction (OER) and safety issues associated with H-2 and O-2 mixing. Here, we replaced the OER with an electrocatalytic oxidative dehydrogenation (EOD) of aldehydes for bipolar H-2 production and achieved industrial-level current densities at cell voltages much lower than during water electrolysis. Experimental and computational studies suggest a reasonable barrier for C-H dissociation on Cu surfaces, mainly through a diol intermediate, with a potential-dependent competition with the solution-phase Cannizzaro reaction. The kinetics of the EOD reaction was further enhanced using a porous CuAg catalyst prepared from a galvanic replacement method. Through Ag incorporation and its modification on the Cu surface, the geometric current density and electrocatalyst durability were significantly improved. Finally, we engineered a bipolar H-2 production system in membrane-electrode assembly-based flow cells to facilitate mass transport, achieving maximum current densities of 248 and 390 mA cm(-2) at cell voltages of 0.4 V and 0.6 V, respectively. The faradaic efficiency of H-2 from both the cathode and anode reactions attained similar to 100%. Taking advantage of the bipolar H-2 production without the issues associated with H-2/O-2 mixing, an inexpensive, easy-to-manufacture dialysis porous membrane was demonstrated to substitute the costly anion exchange membrane, achieving an energy-efficient and cost-effective process in a simple reactor for H-2 production. An estimated H-2 price of $2.51/kg from an initial technoeconomic assessment is competitive with US DoE's "Green H-2" targets.