Enhancing Photoelectrochemical Water Oxidation Efficiency of WO 3 /α‐Fe 2 O 3 Heterojunction Photoanodes by Surface Functionalization with CoPd Nanocrystals

Sunlight can be used to split water into hydrogen and oxygen by means of a photoelectrochemical (PEC) cell. Oxide nanostructures in heterojunction geometry, consisting of anisotropic WO 3 nanostructures coated with a second semiconductor having a narrower band gap, such as α‐Fe 2 O 3 , have emerged as prospective photoanodes. Herein, the integration of monodisperse CoPd nanocrystals (NCs) with α‐Fe 2 O 3 and WO 3 /α‐Fe 2 O 3 heterojunction semiconductor nanostructures for PEC water oxidation is reported. Depositing CoPd NCs on the surface of hematite leads to more stable photocurrent in comparison to the bare electrode, which indicates improved electron–hole separation at the semiconductor/electrolyte interface. Altering the surface of WO 3 /α‐Fe 2 O 3 photoanodes with CoPd NCs induces a cathodic shift of the onset potential and increases photocurrent density from 0.15 to 0.5 mA cm –2 during water oxidation at 1.23 V versus RHE under AM 1.5 G illumination (pH 7).