Against the backdrop of accelerated transformation of the global energy structure and synchronous growth in demand for advanced materials, how to achieve large-scale preparation of high value-added materials while reducing carbon emissions is becoming a core issue in the fields of materials science and energy engineering. Recently, a research team from the University of Cambridge published a study in the journal Nature Energy, providing a new technological path for this problem: by systematically reconstructing the methane pyrolysis and floating catalyst chemical vapor deposition (FCCVD) process, carbon nanotubes and clean hydrogen gas were produced synchronously without producing carbon dioxide by-products throughout the entire process.

The key to this achievement lies in the deep transformation of the process logic of the existing methane pyrolysis system. Methane, as the main component of natural gas and biogas, has long been regarded as an important raw material for hydrogen production and carbon materials. However, the mainstream steam methane reforming process inevitably produces carbon monoxide and carbon dioxide, making it controversial in the "low-carbon hydrogen production" path. In contrast, methane pyrolysis reaction can theoretically directly decompose methane into solid carbon and hydrogen gas, avoiding oxygen participation in the reaction and eliminating the risk of carbon dioxide emissions from the root.

In previous research and industrial practice, methane pyrolysis has been regarded more as one of the preparation routes for carbon nanotubes, and its byproduct hydrogen gas is usually ignored or only exists as an incidental product. The Cambridge University team has noticed that if the hydrogen yield can be significantly improved without sacrificing the quality of carbon nanotubes, methane pyrolysis is expected to be upgraded from a "material process" to a "material energy coupling process". This approach directly points to the long-standing efficiency bottleneck in the FCCVD system.

The traditional FCCVD process uses methane as the carbon source and utilizes gas-phase catalysts to generate high-quality, high aspect ratio carbon nanotubes under high temperature conditions, which has significant advantages in fields such as battery conductive agents and high-end composite materials. But this process highly relies on external hydrogen input to dilute methane and prevent smoke and dust generation. This design imposes dual constraints on FCCVD during the amplification process: on the one hand, it requires a large amount of pre hydrogen production capacity, and on the other hand, the reaction gas usually adopts a one-way flow mode, with a large amount of unreacted methane discharged with the exhaust gas, resulting in low overall atomic utilization efficiency.

The breakthrough of the Cambridge team is precisely based on this "one-way high loss" model. They proposed and validated a multi-stage circulating gas flow scheme, which allows methane to repeatedly pass through the high-temperature pyrolysis zone in the reactor until it is fully converted. This closed system no longer relies on external hydrogen gas, but gradually establishes a suitable gas composition through the reaction itself, thereby suppressing smoke and maintaining the controllable growth of carbon nanotubes.

In the experimental design, researchers constructed a laboratory scale multi pass FCCVD reactor. Methane gas circulates in a high-temperature pyrolysis environment at approximately 1300 ° C. After each round of reaction, only about 1% of the gas is extracted for hydrogen separation, while the remaining gas re enters the reaction zone to continue participating in the reaction. The generated carbon nanotubes were continuously spread and collected, while other hydrocarbons and trace amounts of hydrogen sulfide in the gas phase did not significantly interfere with the growth of carbon nanotubes.

The efficiency improvement brought about by this cyclic strategy is significant. Research data shows that compared to traditional one-way FCCVD reactors, the carbon yield of this system has increased by 8.7 times, while the molar process efficiency, which measures molecular level utilization efficiency, has increased by 446 times. This result means that every gas molecule entering the system is more fully converted and utilized, resulting in a significant reduction in reactor waste emissions.

Further model analysis shows that under industrial parameter conditions, the multi-stage reactor can theoretically convert about 75% of the feed gas in the system into the target product, and the product ratio of carbon nanotubes to hydrogen is about 3:1. This ratio has practical significance for both the service materials industry and hydrogen energy applications: on the one hand, carbon nanotubes can be used as conductive additives for lithium-ion batteries, and their demand is continuously increasing with the expansion of the power battery and energy storage markets; On the other hand, the by-product hydrogen forms a stable output without introducing additional carbon emissions, providing a potential low-carbon source for the hydrogen energy system.

It is worth noting that the research team also validated the composition of renewable gas sources such as biogas by using a mixture of methane and carbon dioxide as the feed. This experimental design further expands the application boundaries of the technology, making it no longer limited to fossil energy systems, but has the possibility of combining with biomass energy and agricultural waste treatment systems. In this scenario, carbon dioxide is no longer directly emitted, but is "locked" in solid carbon materials as part of the feed system, forming a new carbon cycling pathway.

From an industry perspective, the value of this research lies not in disrupting the existing hydrogen production or carbon nanotube industry landscape in the short term, but in demonstrating a highly integrated process approach: by reconstructing the reactor structure and gas management methods, material preparation and energy output can be achieved simultaneously in the same system. This concept of "process coupling" is precisely one of the most scarce capabilities in the current trend of large-scale and low-carbon development of the new materials industry.

Of course, there are still many engineering challenges from laboratory reactors to industrial grade devices, including long-term stability of high-temperature systems, cost of gas separation and circulation control, catalyst lifespan, and consistency in continuous collection of carbon nanotubes. But it can be confirmed that the multi pass FCCVD pathway proposed by the Cambridge University team has provided a new reference frame for methane pyrolysis in terms of reaction efficiency and resource utilization.

Against the backdrop of the parallel growth of global demand for hydrogen energy and advanced carbon materials, this research achievement demonstrates the redefinition of methane, a traditional energy molecule, in a new system: no longer just a fuel or chemical raw material, but a key node connecting clean energy and high-end materials. If this technology can achieve reliable amplification in the future, its impact may surpass a single industry and become a demonstrative underlying process innovation in the low-carbon industrial system.

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