Main Group Element Based Catalysis for Photolytic HX-Splitting

随着全球人口的增加和生活水平的提高，人类对依赖化石燃料的过程的依赖也在增加，这伴随着不必要的二氧化碳排放增加。因此，许多现代科学都被一个共同的目标统一起来--通过寻找这些基于化石燃料的过程的“绿色”替代品来减少全球二氧化碳排放。能源消耗的主要形式是发电，风能和太阳能等替代能源被认为是以可持续方式做到这一点的可行途径。然而，这些方法有其固有的缺点，主要表现在地理限制和功率输出的间歇性。本质上：并不是地球上所有的地区都有相同的风能和太阳覆盖率，即使在那些覆盖率很高的地区，这些自然过程也不是一直都能可靠地运行。因此，必须开发最大化功率输出和有效存储此类电力的方法，以使这些绿色方法在大范围内可靠。关于可再生能源的储存，一种特殊的方法引起了科学界的注意--化学键储存能量。当两个或更多的原子彼此共享电子时，就会产生化学键，导致这些电子存在于键合原子之间的某个地方。这种键的形成导致能量储存在生成的分子中--我们称之为“化学能”。现在的问题是，我们使用什么键，以及我们如何储存产生的分子/燃料？显而易见的出发点是只考虑不会导致全球变暖的燃料--例如，废弃那些含碳的燃料，转而选择那些在形成和燃烧时都会释放出无污染化合物的燃料。出于这个原因，氢的使用，氢，作为一种燃料已经得到了极大的关注。大规模的氢气合成已经是一个既定的和广泛实施的过程，但目前它需要使用一种称为甲烷蒸汽重整的化学过程。顾名思义，这种方法负责美国95%的氢气生产，需要使用甲烷(CH4，也就是天然气)作为主要的化学前体，并导致二氧化碳的释放。显然，当目标是实现净零碳排放时，这种通向氢气的途径是不可行的。因此，需要设计一条新的路线。这一领域的研究人员已经提出了一种最具吸引力的方法--电化学水分离。这意味着：利用电力(自身可持续地产生)将水(H2O)分解成其组成部分--H2和O2。然而，这一过程受到了内在的惩罚，因为水的分裂在能量上是不利的，需要大量的能量投入才能打破强大的O-H键。这个问题可以通过使用不同的原料--化学上更直接的氢卤酸HX(X=F、Cl、Br、I)来简化。HX裂解是一个两电子、两质子的反应，因此降低了与四电子、四质子水裂解反应相关的复杂性。该项目属于EPSRC能源研究主题，其重点是开发能够有效地进行HX裂解反应的新的含磷化合物。传统上，对这一领域的研究集中在使用贵金属来提供类似的结果，但通过将注意力转向更容易获得和丰富的磷，这种方法变得更具吸引力，适合大规模采用。

As global populations increase and standards of living improve, so does humanity's dependence on fossil fuel reliant processes, which is accompanied by an unwanted increase in CO2 emissions. As such, much of modern science is unified by a common goal - to reduce global CO2 emissions by finding "green" alternatives to these fossil fuel-based processes. The dominant form of energy consumption is the generation of electricity, with alternatives such as wind and solar energy considered viable routes to do so in a sustainable manner. However, these approaches have their inherent drawbacks, mainly in the form of geographical constraints and intermittency of power output. Essentially: not all areas of the globe have equal wind and sun coverage, and even in those with plenty, these natural processes do not operate reliably at all times. Therefore, methods of maximising power output and efficiently storing such power must be developed to make these green approaches reliable on a large scale. Concerning the storage of renewable energy, one particular method has caught the attention of the scientific community - energy storage in chemical bonds. The chemical bond arises when two or more atoms share electrons with one another, resulting in these electrons existing somewhere in-between the bonded atoms. The formation of this bond results in energy being stored in the resulting molecule - we call this "Chemical Energy".The question now is - what bonds do we use and how do we store the resulting molecule/fuel?The obvious starting point is to only consider fuels which do not contribute to global warming - for example by scrapping those which contain carbon and opting instead for those which release non- polluting compounds upon both formation and combustion. For this reason, the use of hydrogen, H2, as a fuel has gained significant attention. The large-scale synthesis of hydrogen is already an established and widely implemented procedure, however it currently requires the use of a chemical process known as Methane Steam Reforming. As the name suggests, this method, which is responsible for 95% of hydrogen production in the United States, requires the use of methane (CH4, a.k.a natural gas) as the main chemical precursor and results in the release of CO2. Clearly, this route towards hydrogen is not viable when aiming to achieve net-zero carbon emissions. Therefore, a new route needs to be devised.Efforts in this field have led to one particular approach emerging as most attractive - electrochemical water splitting. What this means is: splitting water (H2O) into its constituent parts - H2 and O2 - using electricity (itself sustainably generated). This process, however, suffers an intrinsic penalty as water- splitting is energetically unfavourable, requiring a large energy input to break strong O-H bonds. This issue may be simplified by using a different feedstock - the chemically more-straightforward hydrohalic acids, HX (X = F, Cl, Br, I). HX-splitting is a two-electron, two-proton reaction, thus reducing the complexities associated with the four-electron, four-proton water-splitting reaction. The focus of this project, which falls within the EPSRC Energy research theme, is to develop new phosphorous- containing compounds which enable the HX-splitting reaction to occur efficiently. Traditionally, research into this field focuses on the use of precious metals to provide a similar result, but by turning attention to the much more accessible and abundant phosphorous, this approach becomes more attractive for large scale adoption.