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，这要归功于其高重量能量密度（142 MJ/kg）和环保用途。通过由可再生能源驱动的水的电解在阴极产生纯氢是一种清洁且理想的方式，然而，水裂解高度依赖于在阳极处具有有效且稳定的析氧反应（OER），以平衡阴极处的析氢反应（HER）。此外，如果水分解用于储存世界能量的相当大一部分，则如果大量的纯化水用于氢燃料生产，则可能出现水分配问题。另一方面，海水是地球上最丰富的含水电解质原料，但其在水裂解过程中的实施提出了许多挑战，特别是对于阳极反应。海水裂解中最严重的挑战是氯阴离子（海水中约0.5 M）。在酸性条件下，OER平衡电位仅略高于析氯的平衡电位，例如，0.130 V，实际上OER是需要高过电位的四电子氧化，而氯析出是具有动力学优势的容易的两电子氧化。虽然氯是一种高价值的产品，但为世界提供氢气所产生的氯量将很快超过需求。而在碱性条件下，OER的平衡电位明显向低值移动，但析氯的平衡电位变化不大，这使得OER的电位域比析氯的电位域相差0.490 V。因此，本项目旨在开发碱性条件下过电位小于0.480 V的高效OER催化剂，以及高效低成本HER催化剂，如过渡金属碳化物和氮掺杂碳纳米材料。

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.