Every time you light up your gas stove to cook, it releases a powerful greenhouse gas into the air. Known as methane, this carbon-based fuel is burned in stoves, engines and power plants worldwide, but also has a global warming effect projected to be 28 to 80 times that of carbon dioxide.
Now, researchers aim to craft a cleaner-burning fuel from methane: hydrogen gas. One promising method is methane ‘cracking’ or pyrolysis, which breaks methane into hydrogen and solid carbon. However, many metal-based catalysts being explored for methane cracking tend to quickly stop working as they get clogged up with carbon deposits.
Jia Zhang, a Principal Scientist at the A*STAR Institute of High Performance Computing (A*STAR IHPC), and Lili Zhang, Division Director of Emerging Technologies at the A*STAR Institute of Sustainability for Chemicals, Energy and Environment (A*STAR ISCE²), are studying how carbon itself might do a better catalytic job, particularly when shaped as graphene: orderly sheets of carbon only one atom thick.
“Graphene is not only good at catalysing methane pyrolysis reactions but can also guide the formation of solid carbon into valuable byproducts for electronics, batteries and strong lightweight materials, making the process more economically attractive,” said Lili Zhang.
In a recent collaboration between A*STAR IHPC, A*STAR ISCE² and ExxonMobil Technology and Engineering, Jia Zhang, Lili Zhang and colleagues explored the atomic-level mechanics of methane pyrolysis on armchair-edged graphene. The team aimed to identify fundamental bottlenecks in the process and guide meaningful improvements to boost its commercial viability.
“It was not clear if or how this deposition plays an active role in catalysis, or changes the catalyst’s behaviour under different conditions,” said Jia Zhang. “A systematic theoretical study allowed us to look at and better understand what happens at the atomic level.”
By combining quantum-mechanical computer simulations with experimental validation, the team mapped out, step by step, how graphene helps split methane into hydrogen and carbon products. The simulations helped them calculate how individual atoms interact during the process, and how stable the different intermediate chemicals are under real temperature and pressure conditions.
“Our study helped identify which reaction steps are the most difficult under different process conditions,” said Jia Zhang. “This helps pinpoint which elementary reactions need to be accelerated and provides clear guidance on how catalysts should be improved to target those steps.”
Among the study’s insights were that graphene edges are far more reactive than the material’s flat interior: simulations revealed that edges effectively lowered the activation energy needed to break methane’s carbon-hydrogen bonds at low temperature. Our experimental results mirror the theoretical trend.
The study’s findings provide new guidance for the directed design of graphene catalysts for more energy-efficient methane pyrolysis, providing an alternative to trial-and-error approaches, noted the researchers. “Understanding how carbon atoms attach, rearrange, and grow at specific sites also helps in designing better processes for producing graphene, graphite, carbon nanotubes and other advanced carbon materials,” added Lili Zhang.
The A*STAR-affiliated researchers contributing to this research are from the A*STAR Institute of Sustainability for Chemicals, Energy and Environment (A*STAR ISCE²) and the A*STAR Institute of High Performance Computing (A*STAR IHPC).
