Experimental investigation of solar hydrogen production via photo-thermal driven steam methane reforming

Solar-driven steam methane reforming (SMR) is a sustainable technology for hydrogen production. For solar energy utilization, photo-thermochemistry combines the advantages of solar photochemistry and thermochemistry, which can utilize the solar energy in the long-wavelength spectrum and the strong activation ability of photons in the short-wavelength spectrum. In this work, the photo-enhanced reaction of solar hydrogen production from SMR using a Co/Al2O3 catalyst is experimentally investigated. The performance of the reaction in different light conditions is compared with those under dark conditions. Results show that the H2 yield by photo-thermochemical reaction (149.9 mmol·h−1·g−1) can be increased by 30.8% at 600 °C compared with the thermochemical reaction (114.6 mmol·h−1·g−1), indicating photo energy can promote the reaction. To achieve hydrogen production rate equivalent to that under light irradiation, a temperature rise of 30–40 °C is needed under thermochemical conditions. In-situ infrared studies demonstrate that light can encourage the formation of methyl (CH3⁎) and hydroxyl (OH⁎) groups, and the enhancement of these key intermediates in SMR reactions promotes hydrogen generation under photo-thermochemical conditions. The photoactivation effect reduces the apparent activation energy by 28.6% and is the main reason for the increase in photo-thermochemical activity. These findings provide valuable guidance on the use of solar energy for steam methane conversion to hydrogen.