【Frontiers in HaiChuan Chemical Technology】Cambridge University has achieved a 446-fold increase in efficiency in producing hydrogen and carbon nanotubes by using multi-cycle reactors

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A team of researchers at the University of Cambridge achieved a 446-fold improvement in efficiency in producing hydrogen and carbon nanotubes by using multi-cycle reactors. In a pyrolysis reactor at a temperature of 1300°C, diluted methane is no longer just a fossil gas; it transforms into two strategic products: hydrogen and carbon nanotubes. There is no combustion, nor is carbon dioxide produced as a byproduct. Only finely controlled chemical reactions and one key principle are required: reusing the gas until it is almost completely exhausted. In this study, researchers from Cambridge University demonstrated the possibility of shutting down the methane cycle inside a reactor, thereby achieving a higher conversion rate than existing systems and opening up an interesting pathway for energy transition and the economy of advanced materials. The key to making this breakthrough lies in improving an existing process: floating catalyst chemical vapor deposition (FCCVD). Traditionally, this method has been used to produce high-quality carbon nanotubes, which are in high demand for use in lithium-ion batteries, electronic products, or composite materials. The problem all along has been: low efficiency. In traditional systems, methane passes through the reactor only once. The unreacted portion will be wasted. Furthermore, external hydrogen is required to prevent soot formation, which makes the process more expensive and complex. A large amount of gas enters, but very little of it is actually useful. The Cambridge team decided to change this logic. They designed a closed-loop system with multiple cycles, rather than a single-cycle system. The gas is circulated repeatedly in the reactor until methane is almost completely consumed. The hydrogen generated is reused within the system, thus eliminating the need for external input. The production of carbon nanotubes (CNTs) and hydrogen – the methane pyrolysis reaction is not new. It obtains solid carbon and gaseous hydrogen by high-temperature decomposition of methane (CH4). It is generally considered a secondary method for producing hydrogen, with very limited output. What happens here is different. Carbon is not deposited in any form, but appears as long, well-structured nanotubes that possess high industrial value. Hydrogen is no longer an almost negligible by-product, but has become a continuous and available flow product. The system can operate properly even when the input gas contains methane and carbon dioxide, a mixture similar to the gas emitted by biogas plants. This detail is not insignificant. It shows that this technology can be used in conjunction with existing infrastructure, without having to rely entirely on pure fossil fuels. The working principle of the multi-step methane pyrolysis reactor is both simple and continuous. After passing through the high-temperature zone each time, about 1% of the gas is extracted; hydrogen is separated out and the deposited nanotubes are collected to form a network. The remaining gases will return to the reactor. Over and over again. This internal recycling significantly reduces waste and completely changes the overall efficiency of the process. Compared to single-cycle reactors, the team observed an 8.7-fold increase in carbon production, and a more than 400-fold increase in molar efficiency (which reflects how many gas molecules are actually utilized). To improve efficiency, in order to test whether this technology could be applied outside the laboratory, researchers fed actual data from industrial plants into the computational model. The results are consistent: multi-step design can convert approximately 75% of the gas into useful products, with the generated nanotubes and hydrogen appearing in a ratio of roughly 3:1. This is not an exaggeration. It is a conservative estimate based on actual industrial conditions. Nevertheless, it represents a significant leap compared to current technologies for producing hydrogen from methane, such as steam reforming, which still generate carbon monoxide and carbon dioxide. This type of reactor will not solve the climate crisis on its own. But it is highly suitable for a more mixed and pragmatic energy future, in which not everything relies on a single \"miracle solution\". It can be used in the short and medium term to reduce carbon emissions in hydrogen production, while fully renewable alternatives are deployed. It can also strengthen the supply chain for key battery materials and reduce external dependence. It can be used in conjunction with biogas plants, agricultural or industrial waste to close cycles that are currently wasted. This is not a technological utopia. This is a specific, measurable, and replicable improvement. That kind of improvement that is subtle yet capable of gradually changing the rules. Sometimes, this is exactly what’s needed. Source: https://fuelcellsworks.com/2025/12/29/energy-innovation/the-university-of-cambridge-creates-a-reactor-that-recycles-99-percent-of-the-gas-to-produce-clean-hydrogen-and-co2-free-carbon-nanotubes