Solar-thermal production of graphitic carbon and hydrogen via methane decomposition

This work reports a process in which concentrated irradiation from a simulated solar source converts methane to high-value graphitic carbon and hydrogen gas. Methane flows within a photo-thermal reactor through the pores of a thin substrate irradiated by several thousand suns at the focal peak. The methane decomposes primarily into hydrogen while depositing highly graphitic carbon that grows conformally over ligaments in the porous substrate. The localized solar heating of the porous substrate serves to capture the solid carbon into a readily extractable and useful form while maintaining active deposition site density with persistent catalytic activity. Results indicate a strong temperature dependence with high decomposition occurring in the central heating zone with concentration factors and temperatures above 1000 suns and 1300 K, respectively. Even with a large flow area through regions of lower irradiation and temperature, methane conversion and hydrogen yields of approx. 70\% are achieved, and 58\% of the inlet carbon is captured in graphitic form.