Collaborative Research Opportunities in Energy with South Africa: Ab-Initio development and testing of fuel cell catalysts

提议者密切参与了与领导一项新的南非催化方案的主要团体举行的会议。该提案是在这些讨论中提出的，鉴于南非即将启动十年战略计划，以及在开普敦大学和Mintek建立新的催化能力中心，该提案是及时的。它与南非能源合作研究机会的目标密切相关。氧气减少可能被认为是我们在能源研究中面临的重大挑战之一。这一领域的成功可能导致低温燃料电池系统的效率至少提高20%，并显著降低燃料电池的成本。在低温燃料电池中，用于氧还原的最活跃和最稳定的催化剂是铂，不幸的是，这种催化剂有些罕见。因此，如今使用直径不断减小的铂颗粒来提供每个贵金属原子的最大量的催化表面。然而，纳米级铂颗粒比本体铂更不稳定，并且提供较差的催化活性。实际上，本体铂显示出每个表面原子的氧还原活性，其比2.5nm颗粒上的原子高约20倍。如果我们能够在这些超小颗粒中实现与散装铂相同的氧还原反应的表面反应性，那么我们将能够生产燃料电池驱动的汽车，其中的贵金属量不会超过当今汽车的催化排气系统中的贵金属量。二元核壳纳米粒子的工程化是实现这一目标的一种有前途的方法。这些催化剂由一个由贵金属壳包围的廉价金属核组成。这种方法的一个明显优点是减少了所需的铂，因为所有的铂都限制在颗粒的表面。此外，这种表面铂的结构和电子性质被改变，可能导致稳定性和活性的改善。文献中报道了几个具有不同核的颗粒示例的制备，表明具有优异的上级催化活性。然而，人们对它们的热力学稳定性知之甚少，也不知道最好的核-壳催化剂的可能组成。该项目的目的是生产一系列稳定的核-壳催化剂，其铂质量活性比相同粒度的铂催化剂的质量活性高20倍。这样的改进将允许当前燃料电池中铂需求下降近20倍，因此显著超过能源部（美国）在所需催化剂性能方面的目标。我们的方法是将计算材料发现与先进的测试程序联系在一起，以有效地映射大范围的可能材料。少量催化剂的合成和测试将被用来向我们保证，计算搜索方法是有效和准确地操作。这项建议得益于我们的南非伙伴正在进行的大量研究投入。他们将匹配该提案所需的人力（一名PDRA，一名博士和工作人员时间），并将承担通过开普敦大学和Mintek的南非氢催化能力中心资助的大部分研究工作。

The proposers have been closely involved in meetings with the key groups leading a new South African programme in catalysis. This proposal has emerged from these discussions, and is timely given the imminent launch of the ten year strategic programme in South Africa, and the establishment of the new Catalysis Competence Centre at the University of Cape Town and Mintek. It is closely aligned to the goals of the Collaborative Research Opportunities in Energy with South Africa call.Oxygen reduction may be considered one of the Grand Challenges faced by us in energy research. Success in this area may lead to at least a 20% improvement in the efficiency of low temperature fuel cell systems and a significant cost reduction in fuel cells. The most active and stable catalyst for oxygen reduction in low temperature fuel cells is platinum, which unfortunately is somewhat rare. Consequently, platinum particles with ever decreasing diameter are employed today to provide the largest amount of catalytic surface per precious metal atom. Yet nano-scale platinum particles are less stable than bulk platinum and provide inferior catalytic activity. Indeed, bulk platinum shows an oxygen reduction activity per surface atom which is about 20-times higher than for an atom on a 2.5 nm particle. If we could achieve the same surface reactivity for the oxygen reduction reaction in these ultra small particles as for bulk platinum, then we would be able to produce fuel cell powered cars with no more precious metal in them than the amount which is in the catalytic exhaust system of today's cars. The engineering of binary core-shell nanoparticles is a promising approach to achieve this goal. These catalysts consist of a core of inexpensive metal surrounded by a shell of precious metal. An obvious advantage of this approach is the reduction in required platinum as all the platinum is restricted to the surface of the particles. Additionally, structural and electronic properties of this surface platinum are altered potentially leading to improved stability and activity. The preparation of a few examples of particles with different cores is reported in the literature with indications of superior catalytic activity. However little is known about their thermodynamic stability, nor the likely composition of the best core-shell catalysts. The aim of this project is to produce a range of stable core-shell catalyst which have a platinum mass activity which is twenty times higher than the mass activity for a platinum catalyst of the same particle size. Such an improvement would allow a near 20-fold drop in platinum requirement in current fuel cells and thus significantly surpass the goals of the Department of Energy (USA) in required catalyst performance. Our approach is to link together both computational materials discovery with advanced testing procedures to efficiently map a large range of possible materials. Synthesis and testing of a small number of catalysts will be utilised to assure us that the computational search approach is operating efficiently and accurately. The proposal benefits from the significant research input being expended by our South African partners. They will match the manpower requested for this proposal (one PDRA, one PhD and staff time), and will take on a significant portion of the research effort funded through the South African Hydrogen Catalysis Competence Centre at the University of Capetown and Mintek.