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

Abstract

Ag-bridged pCN/TiO2 Z-scheme heterojunction composite with faster charges separation for stimulating H2 evolution under UV and visible light in different photo-catalytic reactor systems has been investigated. The photo-catalytic activity was tested using slurry, fixed bed and monolith photo-reactor systems for continuous H2 production from glycerol-water mixture. Using slurry system, Ag-pCN/TiO2 photo-catalyst produced 470 µmol h−1 of H2 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 photo-generated electrons by surface plasmon resonance (SPR) and active sites for H2 production. The parameters study reveals that highest H2 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 H2 production rate of 10150 μmol 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 µmol h−1 cm−3 than slurry reactor (15.77%, 3.615 µmol h-1cm−3) and fixed-bed reactor (1.63%, 3.233 µmol h-1cm−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 H2 production would offer a new opportunity of engineering approach for renewable fuels applications.