Extremely low onset potential of modified Fe2O3 photoanode for water oxidation

The photoelectrochemical (PEC) performance of hematite ( α -Fe 2 O 3 )-based photoanodes is still far from its theoretical value because they are constrained by serious charge recombination and sluggish water oxidation kinetics. Herein, we developed a heterostructural photoanode by coating boron doped graphite carbon nitride nanolayers onto an Fe 2 O 3 nanoarray (BCN/Fe 2 O 3 ), followed by modification with NiCo(OH) x cocatalyst. The constructed NiCo(OH) x /BCN/Fe 2 O 3 demonstrates a significantly improved photocurrent density of 2.7 mA cm −2 at 1.23 V RHE (V versus reversible hydrogen electrode), which is 3.2 times higher than that of pristine Fe 2 O 3 . Additionally, it exhibits an extremely negative onset potential of 0.60 V RHE . Detailed studies reveal that the BCN/Fe 2 O 3 heterojunction endows a driving force for charge separation and establishes a direct pathway for their transport, while NiCo(OH) x acts as a cocatalyst to accelerate the surface water oxidation reaction.