CNTs are grown in large scale by catalytic decomposition of hydrocarbons or oxygen containing compounds in the presence of supported transition metal catalysts such as iron oxide or Ni/SiO₂ but these use non-renewable fuels (methane or hydrocarbons).

Hydrogen is a material of great industrial interest particularly for the desulphurization and/or hydrogenation of aromatic derivatives produced in oil refinering plants. Hydrogen is also used in mixtures with carbon monoxide and nitrogen for the synthesis of methanol, ammonia and liquid hydrocarbon products (Fischer-Tropsch reactions). Moreover, the utilization of hydrogen for fuel-cell type applications is considered to be one of the most promising leads to answer the energy needs of the future. However, the main drawbacks associated with the current production of hydrogen is the use of non-renewable fuels (natural gas or hydrocarbons) and the emission of carbon dioxide during the process.