Constructing Highly Stable CoAl-LDH-Coupled g-C<sub>3</sub>N<sub>4</sub> 2D/2D Heterojunctions for Solar Energy-Driven Conversion of Flared Gas to Syngas through Dry-/Bireforming of Methane
Muhammad Tahir, Rehan Mansoor
Abstract
Fabricating highly stable CoAl-layered double hydroxide (LDH)-anchored graphitic carbon nitride (g-C 3 N 4 ) 2D/2D heterojunction composites for photocatalytic flared gas (methane) reduction with CO 2 through methane dry reforming (MDR) and methane bireforming has been investigated. The self-assembly growth of CoAl-LDH flakes with layered g-C 3 N 4 sheets enables proficient charge carrier separation to provide good photoactivity and stability. The optimized 15 wt % CoAl-LDH/g-C 3 N 4 exhibited efficient syngas production, in which H 2 and CO yield rates were 4.8 and 3.8 folds higher than those of pure CoAl-LDH, respectively. This activity enhancement can be attributed to strong interfacial interaction, higher light absorption, acidic/basic characteristics, and an improved charge-transfer process. With different feed ratios (CH 4 /CO 2 ), the highest syngas production was achieved with a ratio of 1.0, confirming efficient adsorption of both reactants due to the basic characteristics of composites to uptake CO 2 /CH 4 . During photocatalytic CO 2 reduction with CH 4 /H 2 O through the bireforming of methane, lower photoactivity for CO/H 2 production was observed than using MDR due to a competing sorption process. The quantum yield further confirms higher photon flux utilization for continuous CO and H 2 evolution, as evidenced by good recyclability in multiple cycles. This study provides a new opportunity to construct CoAl-LDH-coupled g-C 3 N 4 heterojunctions to utilize natural gas flaring toward syngas production through the dry reforming process. Photocatalytic MDR technology proves to be an excellent option for flared gas utilization for syngas (CO and H 2 ) production in a cleaner environment.