Methane decomposition for hydrogen production: A comprehensive review on catalyst selection and reactor systems

The rampant global energy demand is predominantly met by fossil fuels, resulting in the reduction of their supply and an alarming increase in greenhouse gas (GHG) emissions. These two challenges have fascinated the scientific community in finding solutions to these problems. Hydrogen (H2) as an energy carrier is considered as one of the solutions to address the challenges. Methane (CH4) decomposition is considered a favourable technology for the production of H2 and valuable by-products in the form of carbon nanomaterial. The H2 could be directly used for various applications such as fuel cell technology, transportation fuel, and for the synthesis of chemicals such as ammonia (NH3) and methanol (CH3OH). In the current scenario, demand for COx-free H2 has increased on an annual basis, either in terms of quantity or number of applications and the thermo-catalytic methane decomposition (CDM) process is gaining more attention to produce H2. To improve the H2 yield and quality of the structured carbon by-product, various approaches involving the catalyst and process parameters have been investigated. This review critically discusses various conventional and novel catalyst systems to identify the recent progress for CDM and the way forward. Furthermore, reactor system configurations powered by conventional and renewable energy sources for methane decomposition, as well as their working principles, technical advantages, and limitations are thoroughly discussed. Finally, the various potential applications of carbon nanomaterial are briefly devised.