Nanotube Array-Like WO₃ Photoanode with Dual-Layer Oxygen-Evolution Cocatalysts for Photoelectrocatalytic Overall Water Splitting

The nanotube array-like WO3 (WA) photoanode has been widely utilized in solar-driven photoelectrocatalytic applications due to its excellent light absorption. However, it still suffers from a low quantum efficiency. Herein, double oxygen-evolution catalyst (OEC) layers (FeOOH and NiOOH) were deposited onto the surface of WA with the formation of a WA-FeOOH/NiOOH photoanode (WA-FeNi). The FeOOH greatly decreased the WA/OEC interfacial electron–hole pair recombination rate, while the NiOOH reduced the OEC/electrolyte interfacial electron–hole pairs recombination and promoted the composite’s water oxidation activity significantly. The as-formed WA-FeNi photoanode possessed a photocurrent density of 120 μA/cm2 under simulated sunlight irradiation, which is almost 200% that of WA. The electron–hole separation yield at 0.6 V versus SCE in the former was determined to be 39.3%, which is nearly 2.5 times that of the latter. As a result, the photoanode exhibited superstrong simulated-sunlight-driven photoelectrocatalytic overall water splitting, with a H2 evolution rate of 3.43 μmol cm–2 h–1. This research provides an effective method for constructing a highly active WO3-based photoelectrocatalytic system for overall water splitting.