Enhanced solar hydrogen generation with the direct coupling of photo and thermal energy – An experimental and mechanism study

Abstract

The complementary use of solar light and heat to overcome respective drawbacks, such as low solar spectral utilization in photocatalysis and light-to-heat conversion in thermochemistry has been a popular research topic. The photo-thermochemical synergy effect of solar hydrogen production with methanol steam reforming reactions using Cu/ZnO/Al2O3 catalyst is experimentally investigated in this study. Solar energy directly shines onto the surface of the catalyst, causing the synergistic effect of light and heat. Experimental results show that the photo-thermochemical reaction can reduce the reaction temperature by more than 10 °C at 188 °C compared with the thermochemical reaction, while increasing hydrogen production by 32.9%. Further mechanism studies show that hot electrons excited by the irradiation of sunlight on Cu and ZnO promote the production of the key intermediates (hydroxyl groups) in the process of the thermochemical methanol steam reforming, which can explain the increase in hydrogen yield under photo-thermochemical conditions. These findings are different from thermochemical reactions, and provide a new route for mid-and-low temperature hydrogen production.