Silver loaded protonated graphitic carbon nitride (Ag/pg-C3N4) nanosheets for stimulating CO2 reduction to fuels via photocatalytic bi-reforming of methane

Silver-nanoparticles (Ag-NPs) supported over protonated graphitic-carbon nitride (pg-C3N4) for photocatalytic CO2 reduction in different reforming processes have been investigated. The Ag-NPs/pg-C3N4 samples, prepared by a combined ultrasonic-dispersion and photo-deposition process, were tested for photocatalytic CO2 reduction by H2O, steam reforming of methane (SRM), dry reforming of methane (DRM) and bi-reforming of methane (BRM). Pure g-C3N4 was favourable for CO evolution, while pg-C3N4 promoted both H-2 and CH3OH production. Similarly, yield of CO over 5 wt% Ag/pg-C3N4 was 2.5 times more than CO over the pg-C3N4 and 5.2 times higher than for the g-C3N4 catalyst. This enhancement was evidently due to faster charge separation because of protonation and Ag-loading. More interestingly, performance of photocatalyst was entirely different when using different reforming systems. Enhanced photoactivity was achieved in BRM process compared to SRM and DRM process during efficient utilization of charge carriers. The highest QY was achieved for CO, H-2 and CH3OH production during BRM process. This revealed that photocatalytic BRM is a promising approach for the production of CH3OH, CO and H-2 in a single step. The results of this study fully demonstrate superiority of Ag/pg-C3N4 nanosheets for the development of photocatalytic dry/bi-reforming of methane systems for renewable fuels production.