Ag-La loaded protonated carbon nitrides nanotubes (pCNNT) with improved charge separation in a monolithic honeycomb photoreactor for enhanced bireforming of methane (BRM) to fuels

Well-designed Ag-La modified protonated graphitic carbon nitride nanotubes (pCNNT) are fabricated via a template-free sonicated assisted one-pot hydrothermal method. The structure and properties of the catalyst samples are obtained by XRD, SEM, TEM, EDX, N₂-sorption, XPS, UV–vis DRS and PL spectroscopy characterization techniques. The effect of Ag-La-modified pCNNT is evaluated for different CH₄ reforming processes such as dry reforming of methane (DRM) and bi-reforming of methane (BRM), carried out in a fixed-bed and monolithic honeycomb photoreactor systems under UV and visible light irradiations. The optimized 3%Ag-5%La/pCNNT performance displayed increased productivity under UV-light due to more production of charges with strong ability for cleaving both stable CO₂ and CH₄ molecules. More importantly, the performance of Ag-La loaded pCNNT is 1.45 and 2.10 folds higher for CO and H₂ production, respectively compared with Ag-La loaded pCN nanosheets. CO and H₂ evolutions prevailed in a monolith photoreactor compared to fixed-bed reactor. Besides, the amount of CO, H₂ and CH₃OH are 1.79, 2.12 and 2.13 folds higher in BRM compared to DRM. The improved performance can be ascribed to effective interfacial carrier separation due to Ag-La synergistic effect with suitable redox potentials for BRM process. The quantum yield is significantly enhanced with BRM in the monolithic honeycomb photoreactor loaded with Ag-La modified pCNNTs due to greater photon energy utilization, larger illuminated surface area, improved sorption process and surface reactions with efficient charge carrier utilization for CO₂ reduction and CH₄/H₂O oxidation. Reaction mechanism is proposed to commensurate with the performance of Ag-La/pCNNT for BRM process based on characterization analysis and experimental results. The experimental results could provide guidance for further development of advanced and highly efficient hetero-structures for photocatalytic BRM applications.

1. Tahir, B., Tahir, M. and Amin, N. (2019). Ag-La loaded protonated carbon nitrides nanotubes (pCNNT) with improved charge separation in a monolithic honeycomb photoreactor for enhanced bireforming of methane (BRM) to fuels. Applied Catalysis B: Environmental, 248, pp.167-183.
2. https://doi.org/10.1016/j.apcatb.2019.01.076