Role of Graphene Oxide as a Sacrificial Interlayer for Enhanced Photoelectrochemical Water Oxidation of Hematite Nanorods

Abstract

Photoelectrochemical cells (PECs) with a structure of F-doped SnO 2 (FTO)/graphene oxide (GO)/hematite (α-Fe 2 O 3 ) photoanode were fabricated, in which GO serves as a sacrificial underlayer layer. In contrast to low temperature sintering carried out under a normal atmosphere, high temperature sintering was carried out for the GO underlayer-based hematite photoanodes. The photocurrent density of the PECs with GO underlayers gradually increased as the spin speed of the FTO substrate increased. In particular, GO at a spin speed of 5,000 rpm showed the highest photocurrent of 1.3 mA/cm 2 . The higher performance of the GO/α-Fe 2 O 3 photoanodes was attributed to the improved FTO/α-Fe 2 O 3 interface. When sintered at 800°C for activation of the hematite (FTO/GO/α-Fe 2 O 3 ) photoanodes, the GO layers before being decomposed act as localized hot zones at the FTO/α-Fe 2 O 3 interface. These localized hot zones play a very crucial role in reducing the micro strain (increased crystallinity) which was confirmed from the synchrotron X-ray diffraction studies. The sacrificial GO underlayer may contribute to relaxing the inhomogeneous internal strain of the α-Fe 2 O 3 nanorods and reducing the deformation of FTO to an extent. In other words, the reduction of the micro strain minimizes the lattice imperfections and defects at the FTO/α-Fe 2 O 3 interface, which may enhance the charge collection efficiency, as demonstrated by the impedance measurements. From the EXAFS analysis, it is clearly evident that the sacrificial GO underlayer does not affect the structure of α-Fe 2 O 3 in the short range. The effects of the GO sacrificial layers are restricted to the FTO/α-Fe 2 O 3 interface and they do not affect the bulk properties of α-Fe 2 O 3 .

Fe2PO5‐Encapsulated Reverse Energetic ZnO/Fe2O3 Heterojunction Nanowire for Enhanced Photoelectrochemical Oxidation of Water

“…These images show an interplanar spacing of 0.27 and 0.301 nm, which is in good agreement with the d‐spacing of the α‐Fe 2 O 3 (104) and ZnFe 2 O 4 (220) planes, respectively. This confirms that the iron oxide shell is in α‐Fe 2 O 3 phase and should be generated from FeOOH through phase transition under high‐temperature annealing . The existence of ZnFe 2 O 4 is likely caused by the reaction between ZnO and FeOOH .…”

“…These images show an interplanar spacingo f0 .27 and 0.301 nm, which is in good agreement with the d-spacing of the a-Fe 2 O 3 (104) [21] and ZnFe 2 O 4 (220) [22] planes, respectively.T his confirms that the iron oxide shell is in a-Fe 2 O 3 phase and should be generated from FeOOHt hroughp hase transition under high-temperature annealing. [23] The existence of ZnFe 2 O 4 is likely caused by the reactionb etween ZnO and FeOOH. [24] LinearX -ray mapping shown in Figure 2d In contrast to pristine samples, PH 3 -treated1 0min ZnO/ Fe 2 O 3 core-shell NWse xhibit ar elativelys mooth surface, with as hell thickness of about 13-18 nm along the wire, as shown in Figure 2a',b'.H igh-resolution TEM images (Figure 2e'-g') measuredi nt he edge region of the wire show clear lattice fringes separated by 0.251 and 0.484 nm, whichc orrespond to the a-Fe 2 O 3 (110) [25] and Fe 2 PO 5 (011) [26] planes, respectively.…”

Synthesis and Characterization of a Novel Ternary Hematite Nanocomposites Structure with Fullerene and 2D-Electrochemical Reduced Graphene Oxide for Superior Photoelectrochemical Performance

“…Figure shows the Raman spectra for GO, bare hematite, and hematite nanocomposites photoanodes. The sharp peak at 1317 cm −1 comes from the two photon scatterings of bare hematite photoanode . The Raman spectra of GO present two distinct peaks at 1354 and 1596 cm −1 , while the eRGO/hematite and eRGO/C 60 /hematite nanocomposites photo­anodes show two obvious peaks at 1323 and 1605 cm −1 that correspond to the D‐band and G‐band, respectively.…”

Enhancing Hematite Photoanode Activity for Water Oxidation by Incorporation of Reduced Graphene Oxide

“…The good effect of the thermalt reatment of hematite photoanodesi sw ell described in the literature, showing the remarkable high-temperature dependence of the photoactivity of this material. [42,43] The pristine hematitep hotoanodee xhibited lower performance compared to the three photoanodes containingr GO.…”