TY - JOUR

T1 - Performance of mesoporous α-Fe2O3/g-C3N4 heterojunction for photoreduction of Hg(II) under visible light illumination

AU - Kadi, Mohammad W.

AU - Mohamed, Reda M.

AU - Ismail, A.A.

AU - Bahnemann, D.W.

N1 - Funding information: This project was funded by the Deanship of Scientific Research ( DSR ) at King Abdulaziz University , Jeddah, under grant no. RG-35-130-38 . The authors, therefore, acknowledge DSR for technical and financial support. The N2 adsorption-desorption isotherms of the mesoporous ?-Fe2O3 NPs, g-C3N4, and 6 wt% mesoporous ?-Fe2O3/g-C3N4 nanocomposite were obtained as shown in Fig. 2a. The results revealed that the isotherm type for all synthesized samples was determined to be IV with a H2 hysteresis loop [47,48]. The inflection sharpness resulting at a relative pressure of p/p0 from capillary condensation from 0.5 to 0.92 represented mesoporous structures with a pore geometry with three-dimensional interconnections (Fig. 2a). The surface areas of the mesoporous ?-Fe2O3 NPs and porous g-C3N4 nanosheet were ~120 m2 g?1 and ~220 m2 g?1, respectively (Table 1). The mesoporous ?-Fe2O3/g-C3N4 nanocomposite was reduced to ~147 m2 g?1 at 6 wt% ?-Fe2O3 in the heterojunction nanocomposite, suggesting the introduction of ?-Fe2O3 to the porous g-C3N4 nanosheet, as summarized in Table 1. Interestingly, the introduction of ?-Fe2O3 to the porous g-C3N4 nanosheet did not influence the formed mesoporous structure of pure ?-Fe2O3 NPs. In general, the greater surface area of the newly synthesized mesoporous ?-Fe2O3/g-C3N4 nanocomposites indicates more efficient photoreduction of Hg(II). Furthermore, these mesostructures will not only support diffusion of Hg(II) but will also encourage light penetration within the pores and, hence, promote solar energy absorption. The FT-IR spectra of the g-C3N4 nanosheets and 5 and 6 wt% mesoporous ?-Fe2O3/g-C3N4 nanocomposites are depicted in Fig. 2b. As clearly seen in Fig. 2b, the main stretching mode at the 808 cm?1 peak was observed, indicating the existence of triazine units in the g-C3N4 nanosheets [49]. This peak was slightly shifted at 816 cm?1 for both the 5 and 6 wt% mesoporous ?-Fe2O3/g-C3N4 nanocomposites, indicating an intense interaction between the ?-Fe2O3 NPs and g-C3N4 nanosheets (Fig. 2b) [50]. The intensity of the FTIR peaks of g-C3N4 was weakened with the increase in ?-Fe2O3 content. The stretching mode of the CN-heterocyclic was confirmed by observing the few peaks located at 1250, 1325, 1439, 1575, and 1639 cm?1, as displayed in Fig. 2b [51]. In addition, a broad peak appeared at 3600-3000 cm?1, suggesting the existence of a stretching vibration for NH [51]. The observed peak for the stretching vibration for NH did not shift after incorporation of ?-Fe2O3 NPs into layered g-C3N4. This project was funded by the Deanship of Scientific Research (DSR) at King Abdulaziz University, Jeddah, under grant no. RG-35-130-38. The authors, therefore, acknowledge DSR for technical and financial support.

PY - 2020/10/1

Y1 - 2020/10/1

N2 - In this study, mesoporous α-Fe 2O 3/g-C 3N 4 nanocomposites were constructed with diverse α-Fe 2O 3 contents for photocatalytic Hg(II) reduction under visible light by employing formic acid as a sacrificial donor and compared with either pure mesoporous α-Fe 2O 3 or g-C 3N 4. The α-Fe 2O 3 nanoparticles (NPs) were uniformly dispersed onto a layered g-C 3N 4 nanosheet with a particle size of 5–15 nm. The photocatalytic Hg(II) reduction efficiency of the α-Fe 2O 3/g-C 3N 4 nanocomposites was increased from 41.1% to 90% within 60 min with increasing α-Fe 2O 3 contents (1–6%). Interestingly, the photocatalytic Hg(II) reduction rate of the mesoporous 6%α-Fe 2O 3/g-C 3N 4 nanocomposite was 4.6 times and 6.8 times greater than that of both pure α-Fe 2O 3 NPs and g-C 3N 4 nanosheets, respectively. The key benefits of photocatalytic Hg(II) reduction over the use of mesoporous α-Fe 2O 3/g-C 3N 4 nanocomposites include the high crystallinity, narrow bandgap, large surface area, mesoporous structure, highly dispersed particles and small particle sizes of α-Fe 2O 3, and the use of a construction Z-scheme photocatalyst. The α-Fe 2O 3/g-C 3N 4 photocatalyst exhibited nearly stable photocatalytic Hg(II) reduction activity (for up to five respective recycles) without a significant reduction in photocatalytic efficiency. The obtained results may provide methods for the fabrication and design of new categories of Z-scheme photocatalysts for photocatalytic reduction and oxidation of toxic organic and inorganic pollutants under visible light.

AB - In this study, mesoporous α-Fe 2O 3/g-C 3N 4 nanocomposites were constructed with diverse α-Fe 2O 3 contents for photocatalytic Hg(II) reduction under visible light by employing formic acid as a sacrificial donor and compared with either pure mesoporous α-Fe 2O 3 or g-C 3N 4. The α-Fe 2O 3 nanoparticles (NPs) were uniformly dispersed onto a layered g-C 3N 4 nanosheet with a particle size of 5–15 nm. The photocatalytic Hg(II) reduction efficiency of the α-Fe 2O 3/g-C 3N 4 nanocomposites was increased from 41.1% to 90% within 60 min with increasing α-Fe 2O 3 contents (1–6%). Interestingly, the photocatalytic Hg(II) reduction rate of the mesoporous 6%α-Fe 2O 3/g-C 3N 4 nanocomposite was 4.6 times and 6.8 times greater than that of both pure α-Fe 2O 3 NPs and g-C 3N 4 nanosheets, respectively. The key benefits of photocatalytic Hg(II) reduction over the use of mesoporous α-Fe 2O 3/g-C 3N 4 nanocomposites include the high crystallinity, narrow bandgap, large surface area, mesoporous structure, highly dispersed particles and small particle sizes of α-Fe 2O 3, and the use of a construction Z-scheme photocatalyst. The α-Fe 2O 3/g-C 3N 4 photocatalyst exhibited nearly stable photocatalytic Hg(II) reduction activity (for up to five respective recycles) without a significant reduction in photocatalytic efficiency. The obtained results may provide methods for the fabrication and design of new categories of Z-scheme photocatalysts for photocatalytic reduction and oxidation of toxic organic and inorganic pollutants under visible light.

KW - Heterojunction

KW - Hg(II) photoreduction

KW - Mesoporous

KW - Visible light

KW - α-Fe O /g-C N

UR - http://www.scopus.com/inward/record.url?scp=85086509034&partnerID=8YFLogxK

U2 - 10.1016/j.ceramint.2020.06.087

DO - 10.1016/j.ceramint.2020.06.087

M3 - Article

VL - 46

SP - 23098

EP - 23106

JO - Ceramics international

JF - Ceramics international

SN - 0272-8842

IS - 14

ER -