Hematite-based photoelectrochemical water splitting supported by inverse opal structures of graphene

By coupling ??-Fe2O3 with a 3D graphene inverse opal (3D-GIO) conducting electrode, the short diffusion length of carriers and low absorption coefficient in ??-Fe2O3 for photoelectrochemical applications were successfully addressed. GIO was directly grown on FTO substrate under low temperature conditions, removing the need for a graphene transfer process. ??-Fe2O3 nanoparticles (NPs) were hydrothermally deposited on the surface of GIO, creating ??-Fe2O3/GIO. The photocurrent density of ??-Fe2O3/GIO in water splitting reactions reached 1.62 mA/cm2 at 1.5 V vs RHE, which is 1.4 times greater than that of optimized ??-Fe2O3. The EIS and IPCE data confirm reduced electron-hole recombination and fast electron transfer processes due to the short distance between active materials and the conducting electrode in the ??-Fe2O3/GIO system. Our result may pave the way for designing devices in advanced energy conversion applications as well as a high efficiency hematite-based PEC system.close3

Fabrication of TiO 2 binary inverse opals without overlayers via the sandwich-vacuum infiltration of precursor

A sandwich-vacuum method was demonstrated for the fabrication of titania (TiO2) binary inverse opals with an open surface. In this method, a moisture-stable TiO2 precursor was backfilled into the interstitial spaces of polystyrene binary colloidal crystals (PS bCCs), which served as a template. Removal of the template by calcination yielded TiO2 binary inverse opals with a 3D-ordered macroporous (3DOM) structure. Optical reflectance spectra revealed the existence of a pseudostop band gap in the 3DOMTiO2 samples. The position of the pseudostop band gap shifted to the low-wavelength region as the number ratio of small over large PS spheres was increased in the template. The sandwich-vacuum method proved to be simple and rapid for the fabrication of TiO2 binary inverse opals without overlayers in large domains. The 3DOM TiO2 materials were used as a photocatalyst for the degradation of benzoic acid. Results showed that in comparison to TiO2 nanoparticles prepared under the same sintering conditions, the 3DOM TiO2 materials displayed enhanced photocatalytic activity