Hybrid FeNiOOH/α‐Fe₂O₃/Graphene Photoelectrodes with Advanced Water Oxidation Performance

Abstract

In this study, the photoelectrochemical behavior of electrodeposited FeNiOOH/Fe 2 O 3 /graphene nanohybrid electrodes is investigated, which has precisely controlled structure and composition. The photoelectrode assembly is designed in a bioinspired manner where each component has its own function: Fe 2 O 3 is responsible for the absorption of light, the graphene framework for proper charge carrier transport, while the FeNiOOH overlayer for facile water oxidation. The effect of each component on the photoelectrochemical behavior is studied by linear sweep photovoltammetry, incident photon‐to‐charge carrier conversion efficiency measurements, and long‐term photoelectrolysis. 2.6 times higher photocurrents are obtained for the best‐performing FeNiOOH/Fe 2 O 3 /graphene system compared to its pristine Fe 2 O 3 counterpart. Transient absorption spectroscopy measurements reveal an increased hole‐lifetime in the case of the Fe 2 O 3 /graphene samples. Long‐term photoelectrolysis measurements in combination with Raman spectroscopy, however, prove that the underlying nanocarbon framework is corroded by the photogenerated holes. This issue is tackled by the electrodeposition of a thin FeNiOOH overlayer, which rapidly accepts the photogenerated holes from Fe 2 O 3 , thus eliminating the pathway leading to the corrosion of graphene.

Photoelectrochemical Oxidation in Ambient Conditions Using Earth-Abundant Hematite Anode: A Green Route for the Synthesis of Biobased Polymer Building Blocks

“…Upon doping with fluorine, the J ph at 1.23 V RHE for the modified hematite photoelectrode increased significantly to 0.1, 0.16, and 1.18 mA/cm 2 at pH 4.5, 9.0, and 12.5, respectively (Figure 1 wine color bar), indicating the PEC performance of the α-Fe 2 O 3 photoanode to be enhanced when functionalized with F-doped FeOOH. The effect is attributed to the reduced recombination losses at the surface of the α-Fe 2 O 3 nanorods and enhanced charge transfer through the FeOOH, consistent with recent reports on F-doped hematite for water oxidation [28,29]. Thus, the F-doped FeOOH avoids the corrosion of the hematite electrode surface and enhances charge transfer even in mildly acidic electrolytes.…”

Embedding Metal–Organic Frameworks for the Design of Flexible Hybrid Supercapacitors by Electrospinning: Synthesis of Highly Graphitized Carbon Nanofibers Containing Metal Oxide Nanoparticles

“…For FOCNF, the characteristic Raman peaks at around 217 cm −1 can be assigned to the A 1g modes with peaks at 281 and 383 cm −1 originating from the E g modes of Fe 2 O 3 . [ 37 ] The Raman spectrum of NOCNF contains obvious peaks at around 355, 515, 673, 837, and 1063 cm −1 . The Raman peaks at 355 and 515 cm −1 can be ascribed to the NiO vibrational first‐order phonon (1 P) modes including transverse optical (TO) and longitudinal optical (LO) modes, while the peaks at 673, 837, and 1063 cm −1 correspond to the second‐order phonon (2 P) modes 2P TO , 2P TO+LO , and 2P LO .…”

Spectroelectrochemical and Chemical Evidence of Surface Passivation at Zinc Ferrite (ZnFe2O4) Photoanodes for Solar Water Oxidation

“…Metal oxides have been long pursued as candidate materials for solar water oxidation (photoanode) given their earth‐abundant composition, and specially, their durability under the harsh oxidative conditions associated with the O 2 evolution reaction. [ 3–5 ] However, these materials are prone to a high degree of recombination at the reactive interface, [ 6–9 ] which ultimately limits the photovoltage generated and hence, the photocurrent onset potential ( V on ) obtained, therefore urgently demanding for new strategies to heal this interface. Indeed, several surface passivation routes, involving Ga 2 O 3 , [ 10 ] Al 2 O 3 , [ 11 ] SiO 2 , [ 12 ] and TiO 2 [ 13 ] coatings, have been so far described for well‐established photoanode materials such as α‐Fe 2 O 3 and BiVO 4 .…”