Catalyst development for low-cost large-scale sustainable hydrogen production from seawater and renewable energy

氢被认为是最有前途的清洁能源载体之一，这要归功于它的高重量能量密度(142MJ/kg)和对环境友好的使用。在可再生能源的驱动下，电解水在阴极上生产纯氢是一种清洁和理想的方法，然而，水的分解高度依赖于在阳极上进行高效稳定的析氧反应(OER)，以平衡阴极上的析氢反应(HER)。此外，如果水被用来储存世界上很大一部分能源，如果大量的纯净水被用于生产氢燃料，可能会出现水分配问题。另一方面，海水是地球上最丰富的水溶液电解液原料，但它在分解水过程中的实施面临着许多挑战，特别是对阳极反应。海水分解过程中最严重的挑战是氯离子(海水中约0.5M)。在酸性条件下，OER平衡电位仅略高于析氯平衡电位，例如0.130 V，实际上OER是四电子氧化，需要较高的过电位，而析氯是简单的两电子氧化，具有动力学优势。虽然氯是一种高价值的产品，但向世界供应氢气所产生的氯量将很快超过需求。然而，在碱性条件下，OER的平衡电位显著向低值移动，而氯的析出电位变化不大，这有利于OER高于氯离子的析出，在电位域上相差0.490 V。因此，本项目的目标是开发在碱性条件下超电位低于0.480 V的高效OER催化剂，以及过渡金属碳化物和氮掺杂碳纳米材料等高效低成本的HER催化剂。

Hydrogen is considered one of the most promising clean energy carriers, thanks to its high gravimetric energy density (142 MJ/kg) and environmentally friendly use. It is a clean and desirable way to produce pure hydrogen at the cathode via electrolysis of water driven by renewable energy, however, the water splitting is highly dependent on having an efficient and stable oxygen evolution reaction (OER) at the anode, to counterbalance the hydrogen evolution reaction (HER) at the cathode. Furthermore, if water splitting is used to store a substantial portion of the world's energy, water distribution issues may arise if vast amounts of purified water are used for hydrogen fuel production. On the other hand, seawater is the most abundant aqueous electrolyte feedstock on Earth but its implementation in the water-splitting process presents many challenges, especially for the anodic reaction.The most serious challenges in seawater splitting are posed by the chloride anions (around 0.5 M in seawater). Under acidic conditions, the OER equilibrium potential is only slightly higher than that of chlorine evolution, e.g., by 0.130 V, and in fact the OER is a four-electron oxidation requiring a high over potential while chlorine evolution is a facile two-electron oxidation with a kinetic advantage. While chlorine is a high value product, the amount of chlorine that would be generated to supply the world with hydrogen would quickly exceed demand. Nevertheless, under alkaline conditions, the equilibrium potential of OER is significantly shifted to lower value but that of chorine evolution does not change so much, which facilitates OER over chorine evolution with 0.490 V difference in potential domain. Therefore, this project aims to develop highly efficient OER catalysts with over potential less than 0.480 V under alkaline conditions, as well as highly efficient and low cost HER catalysts such as transitional metal carbides and nitrogen doped carbon nanomaterials.