Earth-abundant catalysts and novel layered 2D perovskites for solar water splitting (H2CAT)

气候变化委员会得出结论，清洁氢生产对于实现英国到2050年净零碳排放的目标至关重要。在英国每年生产的27太瓦时氢气中，只有1太瓦时来自使用可再生能源直接电解水。使用可再生能源生产真正清洁的氢气需要在材料和设备开发方面进行阶段性改变。此外，利用可再生能源生产氢气的最先进方法依赖于昂贵的催化剂，如铂、钌和铱。因此，迫切需要减少对资源有限的材料的依赖。根据亨利·罗伊斯爵士研究所（SHRI）最近制定的一份关于清洁氢生产的战略文件，光化学方法清洁氢生产为英国提供了一个具有吸引力的高风险/高回报的研究活动。SHRI建议，为了使太阳能制氢可行，需要通过开发新的催化剂和光电极材料，将效率从1%提高到10 - 15%。用于水分解的高效PEC电池可能具有颠覆性，而英国在实现和转化这项技术方面处于世界领先地位。为了获得PEC电池用于清洁制氢的优势，必须克服带隙在1 - 2ev之间的光电极长期稳定性的基本限制。光化学电池通常使用半导体/液体，这取决于带边位置，可以引发HER或OER或两者，而在PEC中，半导体通常是宽带隙材料，也可作为光催化剂。对于光化学电池来说，半导体在水介质中必须是稳定的，这是一个关键的挑战。另一方面，使用宽带隙催化剂的PECs是稳定的，但效率在1%左右，因此不适合大规模生产氢气。该提案旨在开拓光电极（阴极和阳极），克服目前使用层状二维卤化物钙钛矿作为极其高效的光吸收剂和电压源的限制-具有了解支撑其稳定性的关键过程的动机，以便实现具有前所未有的能源效率和性能的设备。该提案基于我们最近在HER和OER催化剂方面的突破（Science 2016, Nature Materials 2019），以及在高效稳定的混合钙钛矿太阳能电池方面的开创性工作（Nature, 2018 & 2020）。它还建立在剑桥大学通过SHRI对能源转型材料主题的战略投资基础上。我们的目标是实现带隙可调的层状二维钙钛矿，具有理想的能带偏移，通过机械/环境障碍与廉价且富含土壤的HER和OER催化剂电子耦合，这将解决和克服用简单的设备设计实现高效PEC电池的长期挑战。拟议的工作将支持和影响正在进行的计划和倡议，这些计划和倡议与EPSRC在能源材料方面的几个优先领域相一致。这包括催化剂材料、二维材料和钙钛矿太阳能电池的稳定运行的自适应操作特性。该提案旨在通过使用基于二维催化剂材料和混合钙钛矿作为光电极的高性能PEC电池，实现太阳能制氢的逐步改变和建立一个国际领先的项目，这将增加价值并连接广泛的社区。拟议的工作将为实现基于二维和混合钙钛矿材料的新型设备的深入物理基础知识开辟新的途径，以加速其向高附加值产品的技术准备和商业化发展。

The Committee on Climate Change concluded that clean hydrogen production was essential for meeting UK's goal of net zero carbon emission by 2050. Of the 27 TWh of hydrogen produced per annum in the UK, only 1TWh of comes from direct electrolysis of water using renewable energy sources. The production of truly clean hydrogen using renewable sources requires a step change in the materials and device development. Moreover, the state-of-the-art methods utilizing renewable energy for production of hydrogen rely on expensive catalysts such as platinum, ruthenium and iridium. Thus, there is an urgent need to for reducing reliance on resource limited materials. According to a recent strategic document on clean production of hydrogen developed by the Sir Henry Royce Institute (SHRI), photochemical methods for clean production of hydrogen offer an attractive strand for high risk/high reward research activity for the UK. The SHRI suggests that for solar to hydrogen to be viable, an increase in efficiency from 1% to 10 - 15% is required through development of new catalysts and photo-electrode materials. High efficiency PEC cells for water splitting could be disruptive and the UK is in a world leading position to realize and translate this technology. To reap the benefits of PEC cells for clean hydrogen production, fundamental limitations of long-term stability of photo-electrodes with band gaps between 1 - 2 eV must be overcome. A photochemical cell typically uses semiconductor/liquid, which depending on the band-edge position can initiate HER or OER or both, whereas in a PEC, the semiconductor is usually a wide band-gap material that also serves as the photocatalyst. For photochemical cells, a mandatory requirement is for the semiconductor to be stable in aqueous media and this is a key challenge. On the other hand, PECs employing wide band-gap catalysts are stable but the efficiency is around 1%, thus making them impractical for large scale generation of hydrogen. This proposal aims to pioneer photo-electrodes (cathodes and anodes) that overcome the current limitations using layered 2D halide perovskites as extremely efficient light absorbers and voltage sources - with the motivation to understand key processes that underpin their stability so that devices with unprecedented energy efficiency and performance can be realized. The proposal builds on our recent breakthroughs in HER and OER catalysts (Science 2016, Nature Materials 2019) as well as pioneering work in efficient and stable hybrid perovskite solar cells (Nature, 2018 & 2020). It also builds on strategic investments in the Materials for Energy Transition theme at Cambridge through the SHRI. Our ambition is to achieve band gap tunable layered 2D perovskites with ideal band offsets that are electronically coupled to inexpensive and earth abundant HER and OER catalysts through mechanical/environmental barriers that will address and overcome the long-standing challenge of realizing high efficiency PEC cells with simple device design. The proposed work will underpin and impact ongoing programmes and initiatives aligned with several EPSRC priority areas in energy materials. This includes adaptation operando characterization of catalyst materials, 2D materials and stable operation of perovskites for solar cells. This proposal aims to bring a step-change and establish an internationally leading programme in solar production of hydrogen using high- performance PEC cells based on two-dimensional catalyst materials and hybrid perovskites as photo-electrodes that will add value and connect a broad range of communities. The proposed work will open up new pathways for achieving in-depth fundamental knowledge of physics of novel devices based on 2D and hybrid perovskite materials to accelerate their development towards technological readiness and commercialization in higher value-added products.