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Single-Site Electrocatalytic Flow Reactor for C-C Coupling

Periodic Reporting for period 1 - SSEFR (Single-Site Electrocatalytic Flow Reactor for C-C Coupling)

Période du rapport: 2021-05-01 au 2023-04-30

Catalysis is a fundamental cornerstone of modern society and is used in many industrial processes to accelerate chemical reactions and increase their efficiency. Numerous essential products, such as fuels, pharmaceuticals, fertilizers, and fine chemicals, are made using catalysts. However, certain catalytic processes still rely on methods that involve the use of heat derived from burning fossil fuels, or the use of expensive metals that are being rapidly depleted.
In this Fellowship, we aimed to address these challenges in two ways. Firstly, we wanted to investigate a new class of catalysts, named single-atom catalysts (SACs), in which single metal atoms are entrapped within a ‘support’ material. In particular, we focused on designing SACs that could be activated by electricity or solar irradiation, using conductive or light-activated scaffolds. This approach offers promising alternatives to heat-activated catalysis. Secondly, we chose to work with metals that are more earth-abundant and ubiquitous on our planet. For this reason, this fellowship focused on the use of nickel single-atom catalysts.
Our research provided us with a strategic approach to address some of the pressing challenges facing our society today, such as minimizing the use of precious natural resources (like commonly used transition metals including platinum, palladium, and iridium), while simultaneously embracing the adoption of renewable power sources to drive catalytic processes and meet society's growing demand for essential chemical products.
During the duration of this MSCA fellowship, significant progress has been made in two key areas of research within the field of single-atom catalysis. The first area focuses on the development of a Ni single atom catalyst for the C-O coupling of carboxylic acids and alkyl halides, an important reaction to make greener pharmaceuticals and agrochemicals. In the past, researchers tried using combinations of light-absorbing materials and transition metals for this reaction. However, this approach had drawbacks. It relied on scarce and expensive materials like iridium complexes, and the reaction was not easily scalable or economically viable, due to challenges in downstream processing of the catalyst.
During this MSCA fellowship, we have successfully devised a new catalytic method that allows for the efficient coupling of simple organic building blocks to produce esters. What sets this system apart is that it exclusively employs readily available, earth-abundant components. Moreover, the process exhibits short reaction times, facilitates easy recovery (thanks to the heterogeneous nature of the catalyst), and demonstrates high catalyst stability. These appealing features make our method highly attractive for industrial applications, particularly for the greener manufacturing of fine chemicals and pharmaceuticals. The results were published in Nature Synthesis. Another area of significant progress during this MSCA fellowship involved the fabrication of single-atom electrocatalysts. Our focus was on designing ‘action-specified electrodes’ to enhance the catalytic activity and selectivity for specific organic transformations. Typically, in electrochemical organic synthesis, commercial electrodes like platinum and reticulated vitreous carbon are used. To improve the selectivity, the reactions often require the addition of various homogeneous complexes and additives. Unfortunately, this complicates the scalability of the electrocatalytic method and hampers downstream processing. Therefore, we created a composite material of carbon nanotubes and nickel SACs within a standalone electrode film. The film was characterized and used for generating pharmaceuticals through electricity-driven processes.
Disseminating the project results has been an overall central aspect of this two-year fellowship, and the engagement with the community has been essential to share the progress of our work, and gain insights and advice from other scientists in related disciplines. Besides the direct dissemination of results at scientific conferences and seminars for the general public, we also modified part of Prof. Gianvito Vilé’s course for M.Sc. Chemical Engineering students enrolled at Politecnico di Milano, titled ‘Flow Chemistry’. In 2021, this was altered in order to feature fundamental concepts related to flow photocatalysis and flow electrocatalysis. These lectures served as a means to promote and teach novel and progressive lines of research, along with providing the fundamental concepts required to begin a chemistry/chemical engineering PhD within this sustainable field. Finally, we have used our personal social media tools, along with Politecnico di Milano’s media reach, to promote our work and results to a wider audience, primarily via posts and updates on platforms such as LinkedIn and Twitter.
The strategy of engineering atomically dispersed non-precious metal sites on the surface of a carbonaceous scaffold is a promising approach to enhance the efficiency and atom economy of heterogeneous catalysts. This advancement has significant implications for sustainable and green synthetic chemistry. By moving beyond complex, expensive homogeneous systems that rely on precious metals and generic electrodes, our results represent a significant breakthrough with the potential to impact researchers, chemical manufacturers, and consumers, attracting industrial and political engagement and investment.
More specifically, the application of single-atom photocatalytic and electrocatalytic methods at higher technology readiness levels (TRL 4–6) can contribute to achieving United Nations' Sustainable Development Goals in chemistry and chemical engineering. These benefits include resource conservation, cost reduction, and energy efficiency. Furthermore, precious metals like platinum and palladium, commonly used as catalysts in many industrial processes, are not only expensive but are also a finite resource on our planet. Reducing or eliminating reliance on these elements will make products and processes more affordable, benefiting both consumers and businesses. Such an action will also help preserve the natural environment, reduce the ecological impact of mining activities, and ensure the availability of precious metals for future generations.
Renewable electricity and sunlight are clean and sustainable energy sources. Compared to traditional fossil fuel-based energy sources to power catalytic reactors, renewables can reduce greenhouse gas emissions, thus helping to mitigate climate change. The merger of the renewable energy sector and catalytic reactors which are powered through renewable electricity or direct sunlight will also lead to the creation of various new jobs along the supply chain. This will also prompt further research, development, and technological advancements in the design of catalytic materials and more efficient reactor designs, which in-turn have the potential to spur economic growth, attract investment, and enhance competitiveness in the global market. Finally, by relying on renewable electricity or sunlight to power catalytic reactors, countries can reduce their dependence on fossil fuel imports, which enhances energy security and reduces vulnerability to price fluctuations and geopolitical tensions associated with fossil fuel trade.
SSEFR concept: a greener chemical synthesis using electricity, light, and single-atom catalysis