Enhanced Visible Activities of α-Fe₂O₃ by Coupling N-Doped Graphene and Mechanism Insight

Abstract

In this work, we first have prepared graphene doped with different amounts of N through a one-pot ammonia-modified hydrothermal process and then successfully coupled them with nanocrystalline α-Fe2O3 by a common wet-chemical method. On the basis of the atmosphere-controlled surface photovoltage spectra, time-resolved surface photovoltage responses, and photoinduced hydroxyl radical amount measurements, it is confirmed that the photogenerated charge separation of α-Fe2O3 could be enhanced in N2 or in air atmosphere after coupling with a certain ratio of graphene. It is especially obvious with the graphene doped with a proper amount of nitrogen. This is responsible for the obviously improved visible activities of α-Fe2O3 for photoelectrochemical water oxidation to produce O2 and photocatalytic degradation of gas-phase acetaldehyde and liquid-phase phenol after coupling graphene doped with a proper amount of N species. It is suggested for the first time, mainly by means of N1s XPS data, electrochemical impedance spectra, O2 temperature-programmed desorption curves, surface acidity-related pyridine-adsorbed FT-IR spectra, and electrochemical O2 reduction measurements, that the increased amount of doped quaternary-type N would be quite favorable for photogenerated charge transfer and transportation and for O2 adsorption. As a result, photogenerated charge separation of the resulting N-doped graphene–Fe2O3 nanocomposite is greatly promoted. In addition, the enhanced O2 adsorption of α-Fe2O3 results mainly from the increased surface acidity after coupling with graphene, especially with quaternary-type N-doped graphene. This work would help us to better understand the important roles of doped N in graphene in the fabricated nanocomposites and also provide us with a feasible route to improve visible photocatalytic activities of α-Fe2O3 greatly.

Novel Composites of α‐Fe2O3 Tetrakaidecahedron and Graphene Oxide as an Effective Photoelectrode with Enhanced Photocurrent Performances

“…This result demonstrates that the introduction of graphene decreases the charge-transfer resistance of composite materials, which agreed with the previous paper. [ 53,54 ] α-Fe 2 O 3 with N-doped graphene has been coupled and found the charge transfer resistance decreased after the introduction of graphene. [ 54 ] This complex is responsible for the decrease of onset potential and increase of current density partly.…”

“…[ 53,54 ] α-Fe 2 O 3 with N-doped graphene has been coupled and found the charge transfer resistance decreased after the introduction of graphene. [ 54 ] This complex is responsible for the decrease of onset potential and increase of current density partly. The photocurrent response of α-Fe 2 O 3 /GO and pure α-Fe 2 O 3 electrodes is displayed in Figure 7 c, taking the α-Fe 2 O 3 /GO 3 electrode as representation.…”

Enhanced visible-light activities of porous BiFeO3 by coupling with nanocrystalline TiO2 and mechanism

“…Interestingly, the SS-SPS response peaks are in good agreement with the TS-SPV responses and PL peak intensities as follows. Based on the SS-SPS principles [29], the SPS responses for nanocrystalline material are equivalent to the quick TS-SPV responses. Hence, it is deduced that the separation of visible-light excited charge carriers is greatly improved.…”

Heterojunctions in Composite Photocatalysts

“…4). Combinations with graphene usually improve the performance of hematite for photoelectrochemistry and photocatalysis in visible light [59] or for Li-ion batteries [60].…”