Methane pyrolysis over activated biochar and red mud-biochar composite catalysts for turquoise hydrogen production

As the global demand for hydrogen increases, low-emission hydrogen production methods are necessary. This work explores the use of biochar catalysts for methane pyrolysis to produce CO X -free hydrogen and valuable solid carbon deposits. Biochar was produced via pyrolysis of white spruce in N 2 followed by activation with CO 2 . Composite catalysts were synthesized by co-pyrolyzing biomass with dried and untreated red mud, an iron-rich waste product. Activated white spruce biochar catalysts performed well, with autocatalytic behaviour at 900 °C and above. The presence of red mud in the catalysts aided in methane pyrolysis, improving the methane conversion compared to activated biochar alone. The carbon deposits were characterized as amorphous for the activated biochar and as graphite for the red mud biochars. This work highlights the potential to use biochar as a catalyst for methane pyrolysis and the key characteristics necessary to facilitate conversion, offering further understanding towards developing low-emission hydrogen. • H 2 was produced from methane pyrolysis using biochar and biochar/red mud catalysts. • Biochar catalysts achieved 19.7 % methane conversion at 950 °C over an 8-h test. • Autocatalytic activity is observed with biochar catalysts above 900 °C. • Doping biochar with red mud in select quantities improves methane conversion. • Amorphous carbon and graphite are the deposits found from methane pyrolysis.