Constructing a stable 2D Ti3AlC2 MnAXm cocatalyst-modified gC3N4/CoAl-LDH/Ti3AlC2 heterojunction for efficient dry and bireforming of methane for photocatalytic syngas production

Abstract

2D titanium aluminium carbide (Ti3AlC2) dispersed with cobalt aluminium layered double hydroxide (CoAl-LDH) and graphitic carbon nitride (g-C3N4) was designed to construct heterojunction with promising charge separation. The performance of the nanotextures was tested for gas flaring (CH4) reduction through photocatalytic dry reforming of methane (DRM) and bireforming of methane (BRM) under visible light irradiation. Coupling Ti3AlC2 with CoAl-LDH/g-C3N4 was found promising to enhance visible light absorption and charge carrier separation. Using ternary CoAl-LDH/g-C3N4/Ti3AlC2 composite and the DRM process, the highest yield rate for CO and H2 of 30.29 and 4.74 µmole g-1 h-1 at selectivity 86.46% and 13.53%, respectively were obtained. This photocatalytic efficiency was 8 and 5-fold higher than pure CoAl-LDH. This improved photocatalytic activity can be attributed to interfacial contact with Z-scheme heterojunction integrated with an exfoliated MAX structure for efficient electron conductivity. The effect of the feed ratio was further investigated, which revealed a direct impact on syngas production due to reactant adsorption competition over the catalyst surface. The higher yield rate of CO and H2 were obtained at a CO2/CH4 feed ratio of 1.0 due to equal opportunity to attach both the molecules to maximize the oxidation and reduction reactions. Likewise, stability analysis revealed excellent composite recyclability with continuous syngas production. Performance comparison with the bireforming process (BRM) revealed that adding H2O to the feed mixture generated more protons, activating the reversed water gas shift reaction (RWGSR), thus reducing the productivity of syngas. This study would provide a green and effective strategy towards gas flaring reduction by utilizing CH4 and CO2 simultaneously and reforming them into energy-efficient renewable fuels, which serves the dual purposes of flaring reduction and utilization.