A dual-function photocatalytic system for simultaneous separating hydrogen from water splitting and photocatalytic degradation of phenol in a twin-reactor

Abstract

Coupling photocatalytic H 2 evolution and phenol degradation have drawn much attention on H 2 as clean energy and phenol as an organic pollutant to the environment. Such dual-function reaction can utilize the chemical potential of phenol oxidation to make up the chemical potential required for hydrogen evolution from water splitting. The production of H 2 thus was enhanced via the phenol oxidation. However, H 2 is still needed to be purified from the reaction products by traditional methods. In this study, we demonstrated the simultaneous separation of H 2 using a photo twin-reactor under artificial sunlight, in which the photocatalytic efficiency was substantially increased due to the inhibition of backward reaction by separating H 2 from the products directly. Three Rh-doped SrTiO 3 (STO) photocatalysts calcined at 900, 1100, 1200 ¢XC (named as STO:Rh900, STO:Rh1100, and STO:Rh1200, respectively) were prepared by solid-state fusion reaction, then photo-deposition method was applied to synthesize Pt loading STO:Rh. All photocatalysts were fully characterized by XRD, XPS, UV¡Vvis, SEM, TEM, and DLS. A single reactor and a twin-reactor (Z-scheme system) were systematically designed by using Pt/STO:Rh for H 2 evolution photocatalyst and WO 3 for phenol oxidation photocatalyst, where Fe 3+ /Fe 2+ pairs were served as electron transfer mediators to conduct the dual-function reaction. In the single reactor, the stoichiometric of the dual-function reaction was proposed and with high consistency to the experimental data. By using the twin-reactor, H 2 production rate increased 2.7 times, reaching 1.90 £gmol g ?1 h ?1 , compared to that in the single reactor. Moreover, the H 2 concentration of the gas-phase products increased from 70% (in the single reactor) to 94% owing to the separation function of the twin-reactor, which would significantly reduce the cost for further purification. The effect of phenol concentration on H 2 production in the twin-reactor was also thoroughly investigated. The results showed that increased phenol initial concentration would enhance the production of H 2 . With 200 £gmol L ?1 phenol, the H 2 yield (11.37 £gmol g ?1 in 6-h reaction) was increased by 20% compared to that of pure water splitting. ? 2018 Elsevier B.V.