Solar fuels from sustainable feedstock using Earth-abundant catalysts: Can light drive affordable electrocatalysts for fuel production?

拟议中的研究目标是利用可持续原料和可再生能源合成燃料的新技术。这是一项重要的工作，因为全球五分之三的能源使用是以燃料燃烧的形式用于运输和供暖。虽然太阳能和风能等可再生能源发电正在减少发电过程中的碳排放，但只有五分之二的最终用途能源是以电力的形式出现的。在全球范围内，找到可持续的、具有成本效益的方式来减少运输和供暖的碳排放至关重要。利用唯一无限的可再生能源——太阳能——从二氧化碳原料中合成燃料将是一个理想的解决方案。然而，目前还没有开发出可行的技术。为什么不呢?传统的二氧化碳转化催化剂是基于诺贝尔金属的，价格昂贵，不适合大规模部署。铼是最广泛使用的二氧化碳还原催化剂的基础，非常昂贵和稀有。它的类似物锰的含量是它的130万倍，占地壳的0.1%。2011年，研究人员表明，与二亚胺配体和羰基的mn配合物在减少二氧化碳方面可能比它们的Re类似物更活跃。这些催化剂现在被用于电化学还原，其中电子从“电源”流向电极，然后流向催化剂，最后流向二氧化碳。2016年，我们开发了一种新型的多功能锰基催化剂，可以附着在表面上。我们能否使用可再生能源来激活这些廉价、多功能、地球丰富的催化剂？到目前为止，主要的障碍是这些催化剂是光敏的，我们不能用阳光直接激活它们。我们建议将廉价的催化剂（锰基）与可用的原料（二氧化碳）和可再生能源（太阳能）结合在一个间接利用阳光的装置中。我们将以最近（2016年）在吸光半导体方面取得的进展为基础，研究一种集成技术，这种技术可以提供人们所追求的突破。整体愿景是一种基于板的技术（很像太阳能光伏板），它可以廉价地大批量生产，吸收阳光并将太阳能转移到锚定在吸收光表面的催化剂上。催化剂在水基电解质中注入二氧化碳，来自阳光的能量将二氧化碳还原为CO，这是一种活性中间体，进一步的，众所周知的，反应可以产生燃料。我们的计划是使用一种特殊的光吸收电极（由TiO2保护的Cu2O/AlZnO），该电极已被证明与稀缺的铼基催化剂结合非常有效。我们将用铼代替丰富的锰催化剂，并测量它们的效果。催化剂需要固定在电极上，不能直接暴露在阳光下。我们的研究将通过对催化剂进行化学修饰，将其附着在吸收光的半导体电极上，并从结构的背面照亮吸收电极，从而克服这些限制。此外，我们将建立一个原型工业过程方案，从中我们将研究拟议设备的能源经济性能和碳排放。这将使我们能够评估该技术在减缓气候变化和提供具有成本效益的燃料方面可能产生的影响。我们拥有一支跨越化学、物理、材料和设备以及技术经济分析的专业研究团队，这对此类研究的成功至关重要。总之，找到一种利用太阳能为这些廉价、多功能的催化剂提供动力的方法，将使所有人朝着清洁、可再生的方式生产燃料和能源迈出一大步。它将促进廉价催化剂、材料和设备的研究，提高生活质量——并帮助地球。

The proposed research targets new technology to synthesise fuels from sustainable feedstocks and renewable energy. This is important work since three fifths of all global energy usage is in the form of fuel burning for transportation and heating. While renewable electricity generation from solar and wind amongst others is on track to reduce the carbon emissions of electricity generation, only two fifths of end use energy is in the form of electricity. It is globally critical to find sustainable and cost effective ways to decarbonise transport and heating. Synthesising fuels from CO2 feedstocks using the only infinite source of renewable energy - solar - would be an ideal solution. Yet no viable technology have been developed.Why not?Traditional catalysts for conversion of CO2 are Nobel-metal based, expensive, and not suitable for mass deployment. Rhenium, which is the basis of the most broadly used catalysts for CO2 reduction, is extremely expensive and rare. Its analog, Manganese, is 1.3 million times more abundant, constituting 0.1% of the Earth's crust. In 2011, researchers showed that Mn-complexes with diimine ligands and carbonyls could be even more active then their Re analogs in reducing CO2. These catalysts are used now used in electrochemical reduction, where the electrons flow from the "mains" to the electrode, then to the catalyst, and finally to CO2. In 2016, we developed a new class of versatile Mn-based catalysts which can be attached to surfaces.Can we use renewable energy to activate these cheap, versatile, Earth-abundant catalysts?The major obstacle so far has been that these catalysts are light-sensitive, and we can not use sunlight to activate them directly. We propose to combine the cheap catalysts (Mn-based) with available feedstock (CO2) and renewable energy (solar) in a device which uses sunlight indirectly. We will build on recent (2016) progress in light-absorbing semiconductors and investigate an integrated technology that could provide the sought after breakthrough. The overall vision is a plate based technology (much like a solar photovoltaic panel) that can be manufactured cheaply in high volumes, that absorbs sunlight and transfers the solar energy to a catalyst that is anchored on the light absorbing surface. The catalyst is fed CO2 in a water based electrolyte and the energy from the sunlight reduces the CO2 to CO, a reactive intermediate from which further, well-known, reactions can make fuels.Our plan is to use a particular light absorbing electrode (Cu2O/AlZnO protected by TiO2) that has been shown to be highly effective in combination with scarce rhenium based catalysts. We will substitute Rhenium for highly abundant Manganese catalysts and measure how effective they are. The catalyst needs to be anchored to the electrode and must not be directly exposed to sunlight. Our research will overcome these constraints using chemical modification of the catalyst to attach it to the light-absorbing semiconductor electrode, and by illuminating the absorbing electrode from the back of the structure.In addition, we will build a prototype industrial process scheme from which we will investigate the energy economic performance and carbon emissions of the proposed device. This will allow us to evaluate the likely impact of the technology in terms of mitigation of climate change, and in providing cost effective access to fuels.We have a team of researchers with expertise spanning chemistry, physics, materials and devices, and techno-economic analysis - the cross-section that is vital for such research to succeed. Overall, finding a way to solar-power these cheap, versatile catalysts, will make a huge step forward towards clean, renewable ways of producing fuels, and energy, for all. It will invigorate research in cheaper catalysts, materials and devices, improve quality of life - and help the Planet.