Investigating the performance of liquid and gas phase photoreactors for dynamic H2 production over bimetallic TiO2 and Ni2P dispersed MAX Ti3AlC2 monolithic nanocomposite under UV and visible light

Abstract

Monolithic TiO2 and Ni2P dispersed 2D Ti3AlC2 MAX nanocomposite synthesized by sol-gel method, was investigated for stimulating photocatalytic H2 production. The performance was tested in three types of photoreactors including visible light irradiated slurry, visible and UV light irradiated fixed-bed and monolith photoreactors in batch and continuous operation. Using TiO2/Ni2P/Ti3AlC2 highest H2 production was achieved, which was 1.13, 3.25 and 3.80 times higher compared to TiO2/Ti3AlC2, TiO2/Ni2P and TiO2 samples. Under visible irradiation, slurry photoreactor in continuous operation depicted the highest activity, which was 23.6 and 32.5 times increased than fixed bed and monolith photoreactor, respectively. Using monolith photoreactor operating under UV light, 136 times more H2 was produced compared to monolith photoreactor under visible-light and 1.73 times higher H2 production than slurry photoreactor under visible-light. This was evidently due to higher penetration power of UV irradiations inside the monolith channels. The light penetration was declined when monolith channel length was increased or visible light was employed. With increasing feed composition, H2 production was further increased due to efficient oxidation and reduction reactions. Fixed-bed and monolith photoreactors operating in batch mode under visible light revealed 301 and 20 times higher H2 production than fixed bed and monolith photoreactors under continuous operation. The highest photonic yield and space yield were achieved using slurry photoreactor, while under UV light illuminated monolith showed highest apparent photonic yield and space yield. The findings of this work would be helpful to maximize photocatalytic H2 generation performance using various reactors under visible and UV irradiations.