Effect of macro-structure of Ni-based catalysts on methane splitting systems

• Carbon growth inside a catalytic matrix clogs or destroys catalysts; • Methane splitting catalyzed preferentially over the surface alleviates macrostructural changes; • Ni-based systems self-tune catalyst properties at the micro and nanoscale; • The macroscopic structure of Ni catalysts affects the changes suffered by the nanostructure. Methane splitting, also known as methane decomposition or cracking, is an emergent technology to allow swift energy decarbonization since it produces hydrogen without emitting CO 2 . This work aims at improving hydrogen production from low temperature methane splitting process catalyzed on Ni surfaces. Six different systems were evaluated for their productivity: Ni-foil (pristine and acid treated), Ni particles deposited on α–Al 2 O 3 and on carbon felt, and SiO 2 -Al 2 O 3 -supported Ni catalyst deposited on α–Al 2 O 3 and on carbon felt. Ni-foil displayed negligible hydrogen production even after chemical abrasion treatments were used to increase the surface area. For α–Al 2 O 3 substrates, the coating of Ni/SiO 2 -Al 2 O 3 vastly outperformed the bulk Ni system ( ca . 40 vs 0.011 g H2 ·g Ni –1 total hydrogen production). Depositing bulk Ni on carbon felt improved total hydrogen production to ca . 0.095 g H2 ·g Ni –1 . Ni/SiO 2 -Al 2 O 3 deposited over carbon felt was particularly stable (40 g H2 ·g Ni –1 total hydrogen production), presenting an activity loss rate of ca . 0.011·g H2 ·g Ni –1 ·h −2 , compared to ca . 0.020 g H2 ·g Ni –1 ·h −2 for the Ni/SiO 2 -Al 2 O 3 deposited over α–Al 2 O 3 . Furthermore, the mechanical integrity of the carbon felt-deposited film was shown to be maintained, while the α–Al 2 O 3 -deposited film structure collapsed, due to carbon formation.