Engineering approach in stimulating photocatalytic H2 production in a slurry and monolithic photoreactor systems using Ag-bridged Z-scheme pCN/TiO2 nanocomposite

Ag-bridged pCN/TiO2 Z-scheme heterojunction composite with faster charges separation for stimulating H-2 evolution under UV and visible light in different photo-catalytic reactor systems has been investigated. The photocatalytic activity was tested using slurry, fixed bed and monolith photo-reactor systems for continuous H-2 production from glycerol-water mixture. Using slurry system, Ag-pCN/TiO2 photo-catalyst produced 470 mu mol h(-1) of H-2 which is 8.41 and 9.66 times higher than pCN/TiO2 and pristine TiO2, respectively. The efficiency was improved due to development of heterojunction with faster charges separation, whereas, Ag provides hot photogenerated electrons by surface plasmon resonance (SPR) and active sites for H-2 production. The parameters study reveals that highest H-2 was obtained at pH 7, glycerol concentration of 5 wt% and 0.15 g of catalyst loading. Furthermore, by applying engineering approach Ag-pCN/TiO2 showed H-2 production rate of 10150 mu mol h(-1) using monolith reactor, a 13.36 and 21.6 times higher than fixed-bed and slurry photoreactors. The monolith honeycomb reactor exhibited higher AQY and space yield of 49.15% and 67.67 mu mol h(-1) cm(-3) than slurry reactor (15.77%, 3.615 mu mol h(-1)cm(-3)) and fixed-bed reactor (1.63%, 3.233 mu mol h(-1)cm(-3)). The superior performance of a monolith reactor was due to higher photon flux utilization, large illuminated surface area and processing volume. The schematic of conversional and Z-scheme mechanism of Ag-pCN/TiO2 were proposed based on the results. Thus, excellent performance of catalyst using monolith reactor compared to slurry and fixed-bed reactor for H-2 production would offer a new opportunity of engineering approach for renewable fuels applications.