Maximizing the use of renewable resources requires clean, sustainable and recyclable energy carriers for energy trade and long-term storage. Aluminum is energy dense, plentiful, and recyclable and, when reacted with water, the stored energy is released as hydrogen and heat. In this study, we investigated the use of high-temperature liquid water and supercritical water as oxidizers for coarse aluminum. We performed experiments using a variety of aluminum morphologies, including coarse aluminum pieces measuring up to 3 mm in diameter, and water ranging in temperature from 475 K to 650 K (and the corresponding saturated vapour pressures). Previous studies of aluminum–water reactions have focused on low temperature experiments using catalysts, specialized alloys, or nano-powders to increase reaction efficiency. These low-temperature approaches have been shown to be effective but add complexity and expense and waste the thermal energy of the reaction. Our results show that, without special measures, 100% hydrogen yield is possible from coarse aluminum particles and scrap aluminum, when the reaction temperature and pressure are increased. A change in reaction efficiency was observed at 550 K. Up to this temperature, the 55 μm and 120 μm powders had yields below 30%, the aluminum slugs and 2 mm plate had yields close to zero. At temperatures between 550 K and the supercritical temperature, there was a marked increase in hydrogen yield. At temperatures above 647 K and pressures above 220 bar, the critical point of water, 100% of the theoretical hydrogen yield was achieved across all samples tested. These findings open the door to using aluminum as a recyclable energy carrier for renewable energy.

中文翻译：

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使用超临界水对粗铝进行无催化剂氧化制氢

最大限度地利用可再生资源需要清洁，可持续和可回收的能源载体用于能源贸易和长期储存。铝是能量密集，丰富且可回收的材料，当与水反应时，储存的能量会以氢和热量的形式释放出来。在这项研究中，我们研究了使用高温液态水和超临界水作为粗铝的氧化剂。我们使用各种铝形态进行了实验，包括直径最大为3 mm的粗铝片，以及温度范围为475 K至650 K（以及相应的饱和蒸气压）的水。铝水反应的先前研究集中在使用催化剂，特殊合金或纳米粉末以提高反应效率的低温实验上。这些低温方法已被证明是有效的，但是增加了复杂性和费用，并且浪费了反应的热能。我们的研究结果表明，如果不采取特殊措施，当提高反应温度和压力时，粗铝颗粒和废铝可以实现100％的氢气产率。在550 K下观察到反应效率发生变化。在此温度下，55μm和120μm粉末的产率低于30％，铝块和2 mm板的产率接近于零。在550 K和超临界温度之间的温度下，氢产率显着增加。在高于647 K的温度和高于水的临界点220 bar的压力下，所有测试样品均达到理论氢产量的100％。