Influence of process parameters on direct solar-thermal hydrogen and graphite production via methane pyrolysis

Current hydrogen and carbon production technologies emit massive amounts of CO2 that threaten Earth's climate stability. Here, a new solar-thermal methane pyrolysis process involving flow through a fibrous carbon medium to produce hydrogen gas and high-value graphitic carbon product is presented and experimentally quantified. A 10 kW(e) solar simulator is used to instigate the methane decomposition reaction with direct irradiation in a custom solar reactor. From localized solar heating of fibrous medium, the process reaches steady-state thermal and chemical operation from room temperature within the first minute of irradiation. Additionally, no measurable carbon deposition occurs outside the fibrous medium, leaving the graphitic product in a form readily extractable from the solar reactor. Parametric variations of methane inlet flow rate (10-2000 sccm), solar power (0.92-2.49 kW) and peak flux (1.3-3.5 MW/m(2)), operating pressure (1.33-40 kPa), and medium thickness (0.36-9.6 mm) are presented, with methane conversion varying from 22% to 96%.& COPY; 2023 The Author(s). Published by Elsevier Ltd on behalf of Hydrogen Energy Publications LLC. This is an open access article under the CC BY-NC-ND license (http:// creativecommons.org/licenses/by-nc-nd/4.0/).