Hierarchically arranged γ-NiOOH/β-FeOOH layer supported on modified Molybdenum-BiVO4 thin film for oxygen evolution reaction

Abstract

Due to the slow kinetics of water oxidation, severe surface charge recombination is a significant energy loss that impedes efficient photoelectrochemical performance. Constructing a scheelite bismuth vanadate (BiVO4) electrode with an oxygen evolution catalyst and doping is an effective way to increase the performance of water oxidation. Importantly, this attempt avoids any sacrificial agents and binders. Using a single-step hydrothermal-based method, a nickel-iron (oxy)hydroxide is deposited unlike conventional two-step photoelectrodeposition method onto the surface of BiVO4 doped with 2% molybdenum dopant. Through this method, the as-formed nickel-iron (oxy)hydroxide is in γ-NiOOH and β-FeOOH forms. The difficulty of transporting charge carriers-hole pairs along the BiVO4 is reduced by incorporating molybdenum. A low-cost but efficient co-catalyst, nickel-iron (oxy)hydroxide is introduced to surpass the charge recombination on BiVO4. A comparison of photocurrent density-voltage and photocurrent density-time curves with and without an oxygen evolution catalyst reveals that nickel-iron (oxy)hydroxide accelerates the anodic photocurrent of the BiVO4 from ∼1 to 5 mA cm−2 (1.23 V vs. RHE). Simultaneously, the molybdenum-doped BiVO4 layer with a small band gap and extremely good photoelectrostability and the (oxy)hydroxide layer with good conductivity provide synergetic enhancement of both stability over 12 hours and photocurrent density.