Highly stable honeycomb structured 2D/2D vanadium aluminum carbide MAX coupled g-C3N4 composite for stimulating photocatalytic CO2 reduction to CO and CH4 in a monolith photoreactor

Abstract

Developing efficient materials for photocatalytic conversion of CO2 to value added chemicals and fuels has gained significant attractions in the recent years. However, this is still a difficult task. In this work, a well-designed vanadium aluminum carbide (V2AlC) MAX coupled with porous graphitic carbon nitride (g-CN) to construct a nanocomposite for photocatalytic CO2 reduction has been investigated. 2D/2D V2AlC/g-CN performance was conducted in a fixed-bed and monolith photoreactor under UV and visible light. The V2AlC/g-CN exhibited photoactivity of 1747 and 67 µmol g−1 h−1 for CO and CH4 evolution, which were 4.13 and 1.94 folds more than their production compared to using pristine g-CN, respectively. More importantly, among the sacrificial reagents such as H2O, CH3OH, and H2, the highest productivity was obtained using CO2-CH3OH due to more attachment of methanol over g-C3N4 with more proton generation. Similarly, performance of V2AlC/g-CN under UV-light was promising due to the ability of long pathways to penetrate light inside the fixed bed reactor. In addition to photocatalysts, the performance comparison of reactors confirms that the monolith photoreactor has higher productivity for CO2 reduction to CO and CH4. This was evidently due to the large illuminated active surface area, and more light utilization, and proficient mass transfer inside the monolithic microchannels. The stability examination further confirms the unceasing evolution of CO and CH4 in the consecutive four cycles. Thus, V2AlC MAX is a promising layered material and can be coupled with semiconductors as a support or cocatalyst to achieve both photoactivity and stability for continuous fuel production.