A direct Z-scheme plasmonic AgCl@g-C3N4 heterojunction photocatalyst with superior visible light CO2 reduction in aqueous medium

A direct Z-scheme AgCl@g-C3N4 composite with different ratios of AgCl loaded on g-C3N4 was constructed through modified deposition-precipitation method and as prepared composite was well characterized. The photocatalytic performance efficiency of AgCl@g-C3N4 composite was evaluated for the reduction of CO2 in an aqueous medium under visible light irradiation. The gas chromatographic analysis confirms the formation of methane, acetic acid and formic acid as products. The experimental results indicated that the AgCl@ g-C3N4 composite displays better photocatalytic activity than pure AgCl and g-C3N4. Effects of metal loading concentration (0.5-1.5 wt%), catalyst dosage (1-4 g L-1), reaction medium (triethanolamine (TEA)), water and sodium hydroxide (NaOH)), irradiation time and catalyst stability on the CO2 reduction reaction were investigated. The maximum yield and selectivity of methane, acetic acid and formic acid from CO2 in TEA medium over was about 53.03 lmol g(-1), 6.01 lmol g(-1), 2.51 lmol g(-1) and 88.87%, 10.08% and 1.05% respectively for 8 h, 3 g L-1 of 1% AgCl@g-C3N4. However, no formation of acetic acid and formic acid were observed in the water mediated system. The enhanced photocatalytic activity towards CO2 reduction reaction was attributed to the combination effect of Z-scheme g-C3N4 and AgCl heterojunction, an absence of electron mediator, which efficiently inhibits the recombination rate and improved photocatalytic activity of g-C3N4. This study will provide a new insight for fabrication of Z-scheme g-C3N4 based photocatalytic system for environmental remediation. (C) 2018 Elsevier B.V. All rights reserved.