High Water Oxidation Performance of W‐Doped BiVO₄ Photoanodes Coupled to V₂O₅ Rods as a Photoabsorber and Hole Carrier

Abstract

Monoclinic BiVO 4 is recognized as a promising photoanode for water oxidation, but its relatively wide bandgap energy ( E g ≈2.5 eV) and poor charge transport limit the light absorption ( η abs ) and charge separation ( η sep ) efficiencies, thus resulting in low photocurrents. To solve these drawbacks, here the η abs × η sep product has been decoupled by combining W‐doped BiVO 4 and V 2 O 5 rods ( E g ≈2.1 eV) for simultaneously increasing the light harvesting and the charge separation in photoanodes under back‐side illumination. In this strategy, V 2 O 5 rods maximize the light absorption and hole transport throughout the W‐BiVO 4 film, making more holes to achieve the V 2 O 5 /W‐BiVO 4 /H 2 O interface to trigger the water oxidation reaction with photocurrents as high as 6.6 mA cm −2 at 1.23 V RHE after 2 h reaction. Notably, under back‐side illumination, the W‐BiVO 4 /V 2 O 5 photoanode exhibited η abs × η sep of 74.5 and 93.0% at 0.5 and 1.23 V RHE , respectively, the highest values reported up to date for BiVO 4 ‐based photoelectrodes. This simple strategy brings us closer to develop efficient photoanodes for photoelectrochemical water splitting devices.