Oxygen evolution NiOOH catalyst assisted V2O5@BiVO4 inverse opal hetero-structure for solar water oxidation

Abstract

Abstract Using vanadium oxide (V2O5) inverse opal (IO) as a three-dimensional (3D) electron transporting tunnel, bismuth vanadate (BiVO4) as a light harvester, and Amorphous Nickel Hydroxide (NiOOH) as an oxygen evolution co-catalyst, a V2O5@BiVO4@NiOOH IO architecture was fabricated as an efficient photoanode on a conductive fluorine doped tin oxide (FTO) substrate for photoelectrochemical (PEC) water oxidation. V2O5 is the visible light absorbing photoanodes for water oxidation; however, the efficiency of this compound remains low (∼0.08\xa0mA/cm2 at 1.23\xa0V vs. reversible hydrogen electrode (VRHE)) and the unfavorable surface trap states limits the activity of V2O5 photoelectrodes in a PEC system. We found that the photoactive thin conductive BiVO4 (∼12\xa0nm) in the V2O5 IO greatly enhanced the charge separation efficiency to achieve better PEC water oxidation through modification of the surface states. The subsequent addition of NiOOH as an effective Oxygen evolution catalyst subsequently reduces the large overpotential and generates the photocurrent density of 1.14\xa0mA/cm2 at 1.23 VRHE. Electrochemical impedance spectroscopy (EIS) evidenced that NiOOH deposition can substantially lower the charge transfer resistance (Rct) at the semiconductor interface. Specifically, the consecutive and ordered morphology renders direct conduction pathways for the extraction of photogenerated electron/hole pairs and the convenient structure to penetrate the photogenerated carriers toward the semiconductor surface over the electrolyte. It is expected that the uninterrupted pathways will improve the electron transportation and thus the charge collection properties.